science guruji

Use of Vermi compost in crops

2021-04-08T10:29:00.001+05:30

vermi compost

Vermicomposting is the conversion of dung manure and other agricultural waste by earthworms.

Vermi compost contains 2.5 to 3.0 nitrogen, 1% phosphorus and 1.5% potash elements.

Use of Vermi compost crops

Common crops - 5 tonnes per hectare

Vegetables - 5 - 4 tonne per hectare

Fruit Trees - 5kg per plant

Flower beds - 1-2 kg per square meter

Vitamins and Minerals

2021-01-23T13:59:00.002+05:30

Vitamins and Minerals •

Give examples of vitamins and minerals, and state their functions

How do you get your vitamins?

You may take a vitamin pill. That is a good way to make sure you are getting most of the vitamins your body needs to grow. But the best way to get your vitamins is through eating a healthy diet.

Vitamins and Minerals

Vitamins and minerals are also nutrients. They do not provide energy, but they are needed for good health.

Vitamins

Vitamins are organic compounds that the body needs in small amounts to function properly. Humans need 13 different vitamins. Some of them are listed below (Table 1.2). The table also shows how much of each vitamin you need every day. Vitamins have many roles in the body. For example, Vitamin A helps maintain good vision. Vitamin B9 helps form red blood cells. Vitamin K is needed for blood to clot when you have a cut or other wound.

Some vitamins are produced in the body. For example, vitamin D is made in the skin when it is exposed to sunlight. Vitamins B12 and K are produced by bacteria that normally live inside the body. Most other vitamins must come from foods. Foods that are good sources of vitamins include whole grains, vegetables, fruits, and milk (Table 1.2).

Not getting enough vitamins can cause health problems. For example, too little vitamin C causes a disease called scurvy. People with scurvy have bleeding gums, nosebleeds, and other symptoms

Minerals

Minerals are chemical elements that are needed for body processes. Minerals that you need in relatively large amounts are listed below (Table ). Minerals that you need in smaller amounts include iodine, iron, and zinc.

Minerals have many important roles in the body. For example, calcium and phosphorus are needed for strong bones and teeth. Potassium and sodium are needed for muscles and nerves to work normally.

Your body cannot produce any of the minerals that it needs. Instead, you must get minerals from the foods you eat. Good sources of minerals include milk, leafy green vegetables, and whole grains (Table ).

Not getting enough minerals can cause health problems. For example, too little calcium may cause osteoporosis. This is a disease in which bones become soft and break easily. Getting too much of some minerals can also cause health problems. Many people get too much sodium. Sodium is added to most packaged foods. People often add more sodium to their food by using table salt. Too much sodium causes high blood pressure in some people.

Vocabulary

• mineral: Chemical element, such as calcium or potassium, that is needed for body processes.

• vitamin: Organic compound needed in small amounts for the body to function properly.

BIOTECHNOLOGICAL APPLICATIONS IN MEDICINE

2021-01-03T13:01:00.002+05:30

BIOTECHNOLOGICAL APPLICATIONS IN MEDICINE

The recombinant DNA technological processes have made immense impact in the area of healthcare by enabling mass production of safe and more effective therapeutic drugs. Further, the recombinant therapeutics do not induce unwanted immunological responses as is common in case of similar products isolated from non-human sources. At present, about 30 recombinant therapeutics have been approved for human-use the world over. In India, 12 of these are presently being marketed.

Genetically Engineered Insulin

Management of adult-onset diabetes is possible by taking insulin at regular time intervals. What would a diabetic patient do if enough human-insulin was not available? If you discuss this, you would soon realise that one would have to isolate and use insulin from other animals. Would the insulin isolated from other animals be just as effective as that secreted by the human body itself and would it not elicit an immune response in the human body? Now, imagine if bacterium were available that could make human insulin. Suddenly the whole process becomes so simple. You can easily grow a large quantity of the bacteria and make as much insulin as you need.

Think about whether insulin can be orally administered to diabetic people or not. Why?

Insulin used for diabetes was earlier extracted from pancreas of slaughtered cattle and pigs. Insulin from an animal source, though caused some patients to develop allergy or other types of reactions to the foreign protein. Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphid bridges(Figure-1).

In mammals, including humans, insulin is synthesised as a pro-hormone (like a pro-enzyme, the pro-hormone also needs to be processed before it becomes a fully mature and functional hormone) which contains an extra stretch called the C peptide. This C peptide is not present in the mature insulin and is removed during maturation into insulin.The main challenge for production of insulin using rDNA techniques was getting insulin assembled into a mature form. In 1983, Eli Lilly an American company prepared two DNA sequences corresponding to A and B, chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains. Chains A and B were produced separately, extracted and combined by creating disulfide bonds to form human insulin.

Gene Therapy

If a person is born with a hereditary disease, can a corrective therapy be taken for such a disease? Gene therapy is an attempt to do this. Gene therapy is a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo. Here genes are inserted into a person’s cells and tissues to treat a disease. Correction of a genetic defect involves delivery of a normal gene into the individual or embryo to take over the function of and compensate for the non-functional gene.

The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency. This enzyme is crucial for the immune system to function. The disorder is caused due to the deletion of the gene for adenosine deaminase. In some children ADA deficiency can be cured by bone marrow transplantation; in others it can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection. But the problem with both of these approaches that they are not completely curative. As a first step towards gene therapy, lymphocytes from the blood of the patient are grown in a culture outside the body. A functional ADA cDNA (using a retroviral vector) is then introduced into these lymphocytes, which are subsequently returned to the patient. However, as these cells are not immortal, the patient requires periodic infusion of such genetically engineered lymphocytes. However, if the gene isolate from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.

Molecular Diagnosis

You know that for effective treatment of a disease, early diagnosis and understanding ipathophysiology is very important. Using conventional methods of diagnosis (serum and urine analysis, etc.) early detection is not possible. Recombinant technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-sorbent Assay (ELISA) are some of the techniques that serve the purpose of early diagnosis.

Presence of a pathogen (bacteria,viruses, etc.) is normally suspected only when the pathogen has produced a disease symptom. By this time the concentration of pathogen is already very high in the body. However, very low concentration of a bacteria or virus (at a time when the symptoms of the disease are not yet visible) can be detected by amplification of their nucleic acid by PCR. Can you explain how PCR can detect very low amounts of DNA? PCR is now routinely used to detect HIV in suspected AIDS patients. It is being used to detect mutations in genes in suspected cancer patients too. It is a powerful techqnique to identify many other genetic disorders.

A single stranded DNA or RNA, tagged with a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of cells followed by detection using autoradiography. The clone having the mutated gene will hence not appear on the photographic film, because the probe will not have complementarity with the mutated gene.

ELISA is based on the principle of antigen-antibody interaction. Infection by pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesised against the pathogen.

Structure of Polynucleotide Chain

2020-12-30T22:47:00.000+05:30

THE DNA

DNA is a long polymer of deoxyribonucleotides. The length of DNA is usually defined as number of nucleotides (or a pair of nucleotide referred to as base pairs) present in it. This also is the characteristic of an organism. For example, a bacteriophage known as f ×174 has 5386 nucleotides, Bacteriophage lambda has 48502 base pairs (bp), Escherichia coli has 4.6 × 106 bp, and haploid content of human DNA is 3.3 × 109 bp. Let us discuss the structure of such a long polymer.

Structure of Polynucleotide Chain

Let us recapitulate the chemical structure of a polynucleotide chain (DNA or RNA). A nucleotide has three components – a nitrogenous base, a pentose sugar (ribose in case of RNA, and deoxyribose for DNA), and a phosphate group. There are two types of nitrogenous bases – Purines (Adenine and Guanine), and Pyrimidines (Cytosine, Uracil and Thymine). Cytosine is common for both DNA and RNA and Thymine is present in DNA. Uracil is present in RNA at the place of Thymine. A nitrogenous base is linked to the OH of 1' C pentose sugar through a N-glycosidic linkage to form a nucleoside, such as adenosine or deoxyadenosine, guanosine or deoxyguanosine, cytidine or deoxycytidine and uridine or deoxythymidine. When a phosphate group is linked to OH of 5' C of a nucleoside through phosphoester linkage, a corresponding nucleotide (or deoxynucleotide depending upon the type of sugar present) is formed. Two nucleotides are linked through 3'-5' phosphodiester linkage to form a dinucleotide. More nucleotides can be joined in such a manner to form a polynucleotide chain. A polymer thus formed has at one end a freephosphate moiety at 5' -end of sugar, which is referred to as 5’-end of polynucleotide chain. Similarly, at the other end of the polymer the sugar has a free OH of 3'C group which is referred to as 3' -end of the polynucleotide chain. The backbone of a polynucleotide chain is formed due to sugar and phosphates. The nitrogenous bases linked to sugar moiety project from the backbone (Figure-1)

In RNA, every nucleotide residue has an additional –OH group present at 2' -position in the ribose. Also, in RNA the uracil is found at the place of thymine (5-methyl uracil, another chemical name for thymine).

DNA as an acidic substance present in nucleus was first identified by Friedrich Meischer in 1869. He named it as ‘Nuclein’. However, due to technical limitation in isolating such a long polymer intact, the elucidation of structure of DNA remained elusive for a very long period of time. It was only in 1953 that James Watson and Francis Crick, based on the X-ray diffraction data produced by Maurice Wilkins and Rosalind Franklin, proposed a very simple but famous Double Helix model for the structure of DNA. One of the hallmarks of their proposition was base pairing between the two strands of polynucleotide chains. However, this proposition was also based on the observation of Erwin Chargaff that for a double stranded DNA, the ratios between Adenine and Thymine and Guanine and Cytosine are constant and equals one.

The base pairing confers a very unique property to the polynucleotide chains. They are said to be complementary to each other, and therefore if the sequence of bases in one strand is known then the sequence in other strand can be predicted. Also, if each strand from a DNA (let us call it as a parental DNA) acts as a template for synthesis of a new strand, the two double stranded DNA (let us call them as daughter DNA) thus, produced would be identical to the parental DNA molecule. Because of this, the genetic implications of the structure of DNA became very clear.

The salient features of the Double-helix structure of DNA are as follows:

(i) It is made of two polynucleotide chains, where the backbone is constituted by sugar-phosphate, and the bases project inside.

(ii) The two chains have anti-parallel polarity. It means, if one

chain has the polarity 5'>3', the other has 3'>5' .

(iii) The bases in two strands are paired through hydrogen bond (H-bonds) forming base pairs (bp). Adenine forms two hydrogen bonds with Thymine from opposite strand and vice-versa. Similarly, Guanine is bonded with Cytosine with three H-bonds. As a result, always a purine comes opposite to a pyrimidine. This generates approximately uniform distance between the two strands of the helix (Figure-2).(iv) The two chains are coiled in a right-handed fashion. The pitch of the helix is 3.4 nm (a nanometre is one billionth of a metre, that is 10-9 m) and there are roughly 10 bp in each 2020-turn. Consequently, the distance between a bp in a helix is approximately 0.34 nm.

(v) The plane of one base pair stacks over the other in double helix. This, in addition to H-bonds, confers stability of the helical structure (Figur-3)

Compare the structure of purines and pyrimidines. Can you find out why the distance between two polynucleotide chains in DNA remains almost constant?

The proposition of a double helix structure for DNA and its simplicity in explaining the genetic implication became revolutionary. Very soon, Francis Crick proposed the Central dogma in molecular biology, which states that the genetic information flows from DNAàRNAàProtein.In some viruses the flow of information is in reverse direction, that is, from RNA to DNA. Can you suggest a simple name to the process?

आपका शरीर ठंड के लिए कैसे प्रतिक्रिया करता है?

2020-12-27T01:18:00.004+05:30

आपका शरीर ठंड के लिए कैसे प्रतिक्रिया करता है?

ये लोग बर्फीले पानी में मस्ती कर रहे होंगे, लेकिन उनके शरीर ठंड की प्रतिक्रिया के लिए संघर्ष कर रहे हैं। उदाहरण के लिए, वे कांपना शुरू कर सकते हैं। कंपकंपी शरीर को एक स्थिर तापमान पर लौटने में मदद करती है। शरीर हमेशा काम कर रहा है स्थिरता, या होमोस्टेसिस प्राप्त करें।

होमियोस्टैसिस और प्रतिक्रिया विनियमन

जब आप एक शांत दिन पर बाहर चलते हैं, तो क्या आपके शरीर का तापमान गिरता है? नहीं, आपके शरीर का तापमान स्थिर रहता है लगभग 98.6 डिग्री फ़ारेनहाइट पर। जब आपके आसपास का तापमान बदलता है, तब भी आपका आंतरिक तापमान स्थिर रहता है

वही बदलते परिवेश के बावजूद स्थिर आंतरिक वातावरण बनाए रखने के लिए शरीर की इस क्षमता को होमोस्टेसिस कहा जाता है। होमोस्टैसिस केवल तापमान परिवर्तन से रक्षा नहीं करता है। आपके आंतरिक वातावरण के अन्य पहलू स्थिर भी रहें। उदाहरण के लिए, आपका शरीर आपके द्रव संतुलन को बारीकी से नियंत्रित करता है। आपने देखा होगा कि यदि आप हैं थोड़ा निर्जलित, आपका मूत्र गहरा होता है। ऐसा इसलिए है क्योंकि मूत्र अधिक केंद्रित है और कम पानी में मिलाया जाता है

होमोस्टैसिस को बनाए रखना

तो आपका शरीर होमोस्टैसिस को कैसे बनाए रखता है? आपके आंतरिक वातावरण का नियमन मुख्य रूप से होता है नकारात्मक प्रतिक्रिया। नकारात्मक प्रतिक्रिया एक उत्तेजना के लिए एक प्रतिक्रिया है जो एक चर को एक निर्धारित मूल्य (चित्रा) के करीब रखती है

उदाहरण के लिए, आपके शरीर में एक आंतरिक थर्मोस्टैट है। एक सर्दियों के दिन के दौरान, आपके घर में थर्मोस्टैट को होश आता है एक कमरे में तापमान और हीटर को चालू या बंद करके प्रतिक्रिया करता है। आपका शरीर उसी तरह से कार्य करता है। कब शरीर का तापमान बढ़ जाता है, त्वचा में रिसेप्टर्स और मस्तिष्क को तापमान परिवर्तन की अनुभूति होती है। तापमान में बदलाव होता है मस्तिष्क से एक आदेश चलाता है। यह आदेश कई प्रतिक्रियाओं का कारण बन सकता है।

यदि आप बहुत गर्म हैं, तो त्वचा बनाती है त्वचा की सतह के पास पसीना और रक्त वाहिकाएं फैल जाती हैं। यह प्रतिक्रिया शरीर के तापमान को कम करने में मदद करती है।

सकारात्मक प्रतिक्रिया

शरीर में कुछ प्रक्रियाओं को सकारात्मक प्रतिक्रिया द्वारा नियंत्रित किया जाता है। सकारात्मक प्रतिक्रिया एक घटना की प्रतिक्रिया है जारी रखने के लिए घटना की संभावना बढ़ जाती है। सकारात्मक प्रतिक्रिया का एक उदाहरण नर्सिंग में दूध उत्पादन है माताओं। जैसे ही बच्चा अपनी मां का दूध पीता है,

हार्मोन प्रोलैक्टिन, एक रासायनिक संकेत जारी होता है। जितना अधिक बेबी चूसा, अधिक प्रोलैक्टिन जारी किया जाता है, जिससे अधिक दूध का उत्पादन होता है।

• होमियोस्टेसिस:

एक स्थिर आंतरिक वातावरण रखने की क्षमता; एक स्थिर आंतरिक बनाए रखने के लिए शरीर की क्षमता बदलते परिवेश के बावजूद पर्यावरण।
• हार्मोन:

रासायनिक संदेशवाहक अणु।
• नकारात्मक प्रतिक्रिया: एक उत्तेजना के प्रति प्रतिक्रिया जो एक चर को एक निर्धारित मूल्य के करीब रखती है।
• सकारात्मक प्रतिक्रिया: किसी घटना के प्रति प्रतिक्रिया से घटना के जारी रहने की संभावना बढ़ जाती है।

सारांश •

होमोस्टेसिस शरीर की एक बदलती बाहरी स्थिति के बावजूद एक स्थिर आंतरिक वातावरण बनाए रखने की क्षमता है वातावरण। • होमोस्टैसिस को मुख्य रूप से नकारात्मक प्रतिक्रिया के माध्यम से बनाए रखा जाता है, जब एक उत्तेजना की प्रतिक्रिया एक रहती है एक सेट मान के करीब चर।

मानव जीवविज्ञान

2020-12-27T00:19:00.002+05:30

मानव जीवविज्ञान की परिभाषा

मानव जीव विज्ञान जीव विज्ञान की शाखा है जो मानव और मानव आबादी पर केंद्रित है; यह आनुवांशिकी, पारिस्थितिकी, शरीर रचना विज्ञान और शरीर विज्ञान, नृविज्ञान और पोषण सहित मानव जीव के सभी पहलुओं को शामिल करता है। मानव जीव विज्ञान का संबंध जीव विज्ञान के अन्य क्षेत्रों जैसे चिकित्सा, प्राण जीव विज्ञान और जैविक नृविज्ञान से है।

मानव जीवविज्ञान का इतिहास

मनुष्य उच्च-क्रम की विचार प्रक्रियाओं को प्राप्त करने के बाद से स्वयं को समझने पर केंद्रित है। कोई कह सकता है कि मानव जीव विज्ञान का अध्ययन मनुष्यों के विकास के साथ शुरू हुआ। हालांकि, 20 वीं शताब्दी तक "मानव जीव विज्ञान" शब्द का उपयोग जीव विज्ञान के एक अलग उपक्षेत्र का वर्णन करने के लिए नहीं किया गया था। रेमंड पर्ल, जो जॉन्स हॉपकिन्स विश्वविद्यालय में बायोमेट्रिक और महत्वपूर्ण आँकड़ों के एक प्रोफेसर थे, "मानव जीव विज्ञान" शब्द का उपयोग करने वाले पहले आधुनिक जीवविज्ञानी थे। 1929 में उन्होंने सहकर्मी की समीक्षा की वैज्ञानिक पत्रिका ह्यूमन बायोलॉजी की स्थापना की, जो आज भी मौजूद है।

अतीत में मानव जीवविज्ञान का अधिकांश भाग नस्ल के मुद्दे से संबंधित था। अन्वेषण के युग में शुरुआत से, विभिन्न जातीय समूह एक-दूसरे के साथ अधिक से अधिक बार संपर्क में आए, और यह इस समय के दौरान था कि दौड़ की धारणा विकसित होनी शुरू हो गई थी। 19 वीं और 20 वीं शताब्दी की शुरुआत में, जीवविज्ञानी नस्ल के टाइपोलॉजिकल मॉडल का उपयोग करते थे। इस अवधारणा ने दुनिया की मानव आबादी को भौगोलिक स्थिति और भौतिक लक्षणों की एक छोटी संख्या के आधार पर अलग-अलग श्रेणियों में वर्गीकृत किया। यह पिछले जीवविज्ञानियों के काम पर आधारित था।
उदाहरण के लिए, 18 वीं शताब्दी में, टैक्सोनॉमी कैरोलस लिनियस के पिता ने दुनिया के लोगों को चार श्रेणियों में बांटा था, जहाँ तक कहा गया था कि विभिन्न नस्लीय श्रेणियां मानव प्रजातियों की अलग-अलग उप-प्रजातियाँ थीं। टाइपोलॉजिकल मॉडल ने विभिन्न जातीयताओं के लोगों के बारे में व्यापक, गलत सामान्यीकरण किए, लेकिन इसका उपयोग लगभग 100 वर्षों तक किया गया था, जब तक कि 1940 के दशक के अंत तक। बारीकी से टाइपोलॉजिकल मॉडल से संबंधित यूजीनिक्स आंदोलन था, जिसका उद्देश्य चयनात्मक प्रजनन और प्रजनन के लोगों के कुछ समूहों पर प्रतिबंध लगाने के माध्यम से मानव जाति के आनुवंशिक मेकअप को "सुधार" करना था।
20 वीं शताब्दी की शुरुआत में संयुक्त राज्य अमेरिका में नसबंदी कार्यक्रम किए गए थे। पहले इन कार्यक्रमों को मानसिक रूप से बीमार लोगों की ओर लक्षित किया गया था, लेकिन उन्होंने शराबियों, वेश्याओं, और यहां तक कि ऐसे लोगों को भी लक्षित किया, जिन्हें प्रमोटी, कमजोर दिमाग या पुरानी गरीबी में माना जाता था। लगभग 65,000 अमेरिकी, जिनमें से अधिकांश अल्पसंख्यक थे, उनकी इच्छा के खिलाफ निष्फल कर दिए गए थे। युजीनिक्स ने द्वितीय विश्व युद्ध के पक्ष में हार का सामना किया, खासकर नाजी जर्मनी की भयावहता और हिटलर के यूजीनिक्स सिद्धांतों का उपयोग स्पष्ट होने के बाद।
1940 के दशक में, जनसंख्या मॉडल ने टाइपोलॉजिकल मॉडल को बदल दिया। यह मॉडल इस विचार पर आधारित था कि समान लक्षणों वाले लोगों के समूह पूर्वजों से आते हैं जो हजारों वर्षों से अलग-अलग प्रजनन आबादी में एक-दूसरे के साथ रहते हैं। हालांकि, पूरे मानव इतिहास में, आबादी अक्सर पलायन और अंतर्विवाहित रही है, इसलिए जनसंख्या मॉडल पूरी तरह से सटीक नहीं है। यह वास्तव में केवल बहुत कम पृथक समूहों का अध्ययन करने के लिए उपयोग किया जा सकता है जो आज मौजूद हैं। 1960 के दशक में, क्लिनल मॉडल विकसित किया गया था, जो बताता है कि लक्षण धीरे-धीरे एक भौगोलिक स्थान से अगले तक बदलते हैं। उदाहरण के लिए, रक्त वाहिकाओं में बी एलील की आवृत्ति धीरे-धीरे बढ़ जाती है क्योंकि एक यूरोप से एशिया की यात्रा करता है। क्लिनल मॉडल कई (लेकिन सभी नहीं) मानव लक्षणों का वर्णन कर सकता है। आज के विचार, आधुनिक आनुवंशिकी अनुसंधान द्वारा सहायता प्राप्त, यह है कि चूंकि सभी मनुष्य एक दूसरे के समान कम से कम 99.9% हैं, इसलिए लोगों की अलग-अलग दौड़ वास्तव में मौजूद नहीं है; जबकि अलग-अलग जातीय हैं, दौड़ एक सामाजिक निर्माण है।
वर्तमान में, मानव जीव विज्ञान का क्षेत्र बहुत विविध है, लेकिन मनुष्यों के अध्ययन का अधिकांश ध्यान अब एक आनुवांशिकी दृष्टिकोण से है और 20 वीं शताब्दी की कई वैज्ञानिक प्रगति के पथ पर जारी है, जैसे कि आनुवंशिक सामग्री डीएनए की खोज। इसकी संरचना। अनुसंधान विषयों के कुछ उदाहरण माइटोकॉन्ड्रियल डीएनए हैं, जो पूरी तरह से मातृ रेखा, विभिन्न आबादी के बीच स्वास्थ्य संबंधी असमानताओं (जो विभिन्न प्रकार के आनुवंशिक और पर्यावरणीय प्रभावों के कारण हो सकते हैं), और प्राचीन मनुष्यों के विकास और प्रवासन के माध्यम से पारित हो जाते हैं।

Myst ery of space

2020-12-26T10:02:00.000+05:30

Myst ery of space

Usually when we boil water, many bubbles are formed in it. But this does not happen in space. A large bubble is formed when the water is heated there. The reason is also gravity.

Studies on germs for 30 years have shown that germs spread more rapidly in space than on Earth
and are also more dangerous.

Drinking soda in space can be dangerous. There is difficulty in digesting soda here. It is also
because of gravity. This is the reason why experiments are being done on space beer in Australia

BIOTECHNOLOGICAL APPLICATIONS IN AGRICULTURE

2020-12-25T15:10:00.002+05:30

Biotechnology, as you would have learnt from the previous chapter, essentially deals with industrial scale production of biopharmaceuticals and biologicals using genetically modified microbes, fungi, plants and animals. The applications of biotechnology include therapeutics, diagnostics, genetically modified crops for agriculture, processed food, bioremediation, waste treatment, and energy production. Three critical research areas of biotechnology are:
(i) Providing the best catalyst in the form of improved organism usually a microbe or pure enzyme.
(ii) Creating optimal conditions through engineering for a catalyst to act, and
(iii) Downstream processing technologies to purify the protein/organic compound.
Let us now learn how human beings have used biotechnology to improve the quality of human life, especially in the field of food production and health.

BIOTECHNOLOGICAL APPLICATIONS IN AGRICULTURE

Let us take a look at the three options that can be thought for increasing food production

(i) agro-chemical based agriculture;

(ii) organic agriculture; and

(iii) genetically engineered crop-based agriculture.

The Green Revolution succeeded in tripling the food supply but yet it was not enough to feed the growing human population. Increased yields have partly been due to the use of improved crop varieties, but mainly due to the use of better management practices and use of agrochemicals (fertilisers and pesticides). However, for farmers in the developing world, agrochemicals are often too expensive, and further increases in yield with existing varieties are not possible using conventional breeding. Is there any alternative path that our understanding of genetics can show so that farmers may obtain maximum yield from their fields? Is there a way to minimise the use of fertilisers and chemicals so that their harmful effects on the environment are reduced? Use of genetically modified crops is a possible solution.

Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO). GM plants have been useful in many ways. Genetic modification has:

(i) made crops more tolerant to abiotic stresses (cold, drought, salt, heat).

(ii) reduced reliance on chemical pesticides (pest-resistant crops).

(iii) helped to reduce post harvest losses.

(iv) increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil).

(v) enhanced nutritional value of food, e.g., golden rice, i.e., Vitamin ‘A’ enriched rice.

In addition to these uses, GM has been used to create tailor-made plants to supply alternative resources to industries, in the form of starches, fuels and pharmaceuticals.

Some of the applications of biotechnology in agriculture that you will study in detail are the production of pest resistant plants, which could decrease the amount of pesticide used. Bt toxin is produced by a bacterium called Bacillus thuringiensis (Bt for short). Bt toxin gene has been cloned from the bacteria and been expressed in plants to provide resistance to insects without the need for insecticides; in effect created a bio-pesticide. Examples are Bt cotton, Bt corn, rice, tomato, potato and soyabean etc.

Bt Cotton:

Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes). B. thuringiensis forms protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein. Why does this toxin not kill the Bacillus? Actually, the Bt toxin protein exist as inactive protoxins but once an insect ingest the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilise the crystals. The activated toxin binds to the surface of midgut epithelial cells andcreate pores that cause cell swelling and lysis and eventually cause death of the insect.

Specific Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton (Figure-1). The choice of genes depends upon the crop and the targeted pest, as most Bt toxins are insect-group specific. The toxin is coded by a gene cryIAc named cry. There are a number of them, for example, the proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms, that of cryIAb controls corn borer.

(Figure-1) - Cotton boll: (a) destroyed by bollworms; (b) a fully mature cotton boll

Pest Resistant Plants: Several nematodes parasitise a wide variety of plants and animals including human beings. A nematode Meloidegyne incognitia infects the roots of tobacco plants and causes a great reduction in yield. A novel strategy was adopted to prevent this infestation which was based on the process of RNA interference (RNAi). RNAi takes place in all eukaryotic organisms as a method of cellular defense. This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing). The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate.

Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant (Figure 12.2). The introduction of DNA was such that it produced both sense and anti-sense RNA in the host cells. These two RNA’s being complementary to each other formed a double stranded (dsRNA) that initiated RNAi and thus, silenced the specific mRNAof the nematode. The consequence was that the parasite could not survive in a transgenic host expressing specific interfering RNA. The transgenic plant therefore got itself protected from the parasite (Figure-2)

(Figure-2)Host plant-generated dsRNA triggers protection against nematode infestation:(a) Roots of a typical control plants; (b) transgenic plant roots 5 days after deliberateinfection of nematode but protected through novel mechanism

BIODIVERSITY

2020-12-22T14:47:00.004+05:30

BIODIVERSITY

In our biosphere immense diversity (or heterogeneity) exists not only at the species level but at all levels of biological organisation ranging from macromolecules within cells to biomes. Biodiversity is the term popularised by the sociobiologist Edward Wilson to describe the combined diversity at all the levels of biological organisation. The most important of them are–

(i) Genetic diversity: A single species might show high diversity at the genetic level over its distributional range. The genetic variation shown by the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges might be in terms of the potency and concentration of the active chemical (reserpine) that the plant produces. India has more than 50,000 genetically different strains of rice, and 1,000 varieties of mango.

(ii) Species diversity: The diversity at the species level, for example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.

(iii) Ecological diversity: At the ecosystem level, India, for instance, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows has a greater ecosystem diversity than a Scandinavian country like Norway. It has taken millions of years of evolution, to accumulate this rich diversity in nature, but we could lose all that wealth in less than two centuries if the present rates of species losses continue. Biodiversity and its conservation are now vital environmental issues of international concern as more and more people around the world begin to realise the critical importance of biodiversity for our survival and well- being on this planet.

How Many Species are there on Earth and How Many in India?

Since there are published records of all the species discovered and named, we know how many species in all have been recorded so far, but it is not easy to answer the question of how many species there are on earth. According to the International Union for Conservation of Nature and Natural Resources (IUCN) (2004), the total number of plant and animal species described so far is slightly more than 1.5 million, but we have no clear idea of how many species are yet to be discovered and described. Estimates vary widely and many of them are only educated guesses. For many taxonomic groups, species inventories are more complete in temperate than in tropical countries. Considering that an overwhelmingly large proportion of the species waiting to be discovered are in the tropics, biologists make a statistical comparison of the temperate-tropical species richness of an exhaustively studied group of insects and extrapolate this ratio to other groups of animals and plants to come up with a gross estimate of the total number of species on earth. Some extreme estimates range from 20 to 50 million, but a more conservative and scientifically sound estimate made by Robert May places the global species diversity at about 7 million.

Let us look at some interesting aspects about earth’s biodiversity based on the currently available species inventories. More than 70 per cent of all the species recorded are animals, while plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) comprise no more than 22 per cent of the total. Among animals, insects are the most species-rich taxonomic group, making up more than 70 per cent of the total. That means, out of every 10 animals on this planet, 7 are insects. Again, how do we explain this enormous diversification of insects? The number of fungi species in the world is more than the combined total of the species of fishes, amphibians, reptiles and mammals. biodiversity is depicted showing species number of major taxa.

Representing global biodiversity: proportionate number of

species of major taxa of plants, invertebrates and vertebrates

FigureIt should be noted that these estimates do not give any figures for prokaryotes. Biologists are not sure about how many prokaryotic species there might be. The problem is that conventional taxonomic methods are not suitable for identifying microbial species and many species are simply not culturable under laboratory conditions. If we accept biochemical or molecular criteria for delineating species for this group, then their diversity alone might run into millions. Although India has only 2.4 per cent of the world’s land area, its share of the global species diversity is an impressive 8.1 per cent. That is what makes our country one of the 12 mega diversity countries of the world. Nearly 45,000 species of plants and twice as many of animals have been recorded from India. How many living species are actually there waiting to be discovered and named? If we accept May’s global estimates, only 22 per cent of the total species have been recorded so far. Applying this proportion to India’s diversity figures, we estimate that there are probably more than 1,00,000 plant species and more than 3,00,000 animal species yet to be discovered and described. Would we ever be able to complete the inventory of the biological wealth of our country? Consider the immense trained manpower (taxonomists) and the time required to complete the job. The situation appears more hopeless when we realise that a large fraction of these species faces the threat of becoming extinct even before we discover them. Nature’s biological library is burning even before we catalogued the titles of all the books stocked there.

POPULATION STABILISATION AND BIRTH CONTROL IN INDIA

2020-12-19T18:05:00.003+05:30

POPULATION STABILISATION AND BIRTH CONTROL

In the last century an all-round development in various fields significantly improved the quality of life of the people. However, increased health facilities along with better living conditions had an explosive impact on the growth of population. The world population which was around 2 billion (2000 million) in 1900 rocketed to about 6 billion by 2000 and 7.2 billion in 2011. A similar trend was observed in India too. Our population which was approximately 350 million at the time of our independence reached close to the billion mark by 2000 and crossed 1.2 billion in May 2011. A rapid decline in death rate, maternal mortality rate (MMR) and infant mortality rate (IMR) as well as an increase in number of people in reproducible age are probable reasons for this. Through our Reproductive Child Health (RCH) programme, though we could bring down the population growth rate, it was only marginal. According to the 2011 census report, the population growth rate was less than 2 per cent, i.e., 20/1000/year, a rate at which our population could increase rapidly. Such an alarming growth rate could lead to an absolute scarcity of even the basic requirements, i.e., food, shelter and clothing, in spite of significant progress made in those areas. Therefore, the government was forced to take up serious measures to check this population growth rate.

The most important step to overcome this problem is to motivate smaller families by using various contraceptive methods. You might have seen advertisements in the media as well as posters/bills, etc., showing a happy couple with two children with a slogan Hum Do Hamare Do (we two, our two). Many couples, mostly the young, urban, working ones have even adopted an ‘one child norm’. Statutory raising of marriageable age of the female to 18 years and that of males to 21 years, and incentives given to couples with small families are two of the other measures taken to tackle this problem. Let us describe some of the commonly used contraceptive methods, which help prevent unwanted pregnancies.

An ideal contraceptive should be user-friendly, easily available, effective and reversible with no or least side-effects. It also should in no way interfere with the sexual drive, desire and/or the sexual act of the user. A wide range of contraceptive methods are presently available which could be broadly grouped into the following categories, namely Natural/Traditional, Barrier, IUDs, Oral contraceptives, Injectables, Implants and Surgical methods.

Natural methods work on the principle of avoiding chances of ovum and sperms meeting. Periodic abstinence is one such method in which the couples avoid or abstain from coitus from day 10 to 17 of the menstrual cycle when ovulation could be expected. As chances of fertilisation are very high during this period, it is called the fertile period. Therefore, by abstaining from coitus during this period, conception could be prevented. Withdrawal or coitus interruptus is another method in which the male partner withdraws his penis from the vagina just before ejaculation so as to avoid insemination. Lactational amenorrhea (absence of menstruation) method is based on the fact that ovulation and therefore the cycle do not occur during the period of intense lactation following parturition. Therefore, as long as the mother breast-feeds the child fully, chances of conception are almost nil. However, this method has been reported to be effective only upto a maximum period of six months following parturition. As no medicines or devices are used in these methods, side effects are almost nil. Chances of failure, though, of this method are also

In barrier methods, ovum and sperms are prevented from physically meeting with the help of barriers. Such methods are available for both males and females. Condoms are barriers made of thin rubber/ latex sheath that are used to cover the penis in the male or vagina and cervix in the female, just before coitus so that the ejaculated semen would not enter into the female reproductive tract. This can prevent conception. ‘Nirodh’ is a popular brand of condom for the male. Use of condoms has increased in recent years due to its additional benefit of protecting the user from contracting STIs and AIDS. Both the male and the female condoms are disposable, can be self-inserted and thereby gives privacy to the user. Diaphragms, cervical caps and vaults are also barriers made of rubber that are inserted into the female reproductive tract to cover the cervix during coitus. They prevent conception by blocking the entry of sperms through the cervix. They are reusable. Spermicidal creams, jellies and foams are usually used alongwith these barriers to increase their contraceptive efficiency.

Another effective and popular method is the use of Intra Uterine Devices (IUDs). These devices are inserted by doctors or expert nurses in the uterus through vagina. These Intra Uterine Devices are presently available as the non-medicated IUDs (e.g., Lippes loop), copper releasing IUDs (CuT, Cu7, Multiload 375) and the hormone releasing IUDs (Progestasert, LNG-20) . IUDs increase phagocytosis of sperms within the uterus and the Cu ions released suppress sperm motility and the fertilising capacity of sperms. The hormone releasing IUDs, in addition, Condom for female Condom for male make the uterus unsuitable for implantation and the cervix hostile to the sperms. IUDs are ideal contraceptives for the females who want to delay pregnancy and/or space children. It is one of most widely accepted methods of contraception in India.

Oral administration of small doses of either progestogens or progestogen–estrogen combinations is another contraceptive method used by the females. They are used in the form of tablets and hence are popularly called the pills. Pills have to be taken daily for a period of 21 days starting preferably within the first five days of menstrual cycle. After a gap of 7 days (during which menstruation occurs) it has to be repeated in the same pattern till the female desires to prevent conception. They inhibit ovulation and implantation as well as alter the quality of cervical mucus to prevent/retard entry of sperms. Pills are very effective with lesser side effects and are well accepted by the females. Saheli –the new oral contraceptive for the females contains a non-steroidal preparation. It is a ‘once a week’ pill with very few side effects and high contraceptive value.

Progestogens alone or in combination with estrogen can also be used by females as injections or implants under the skin . Their mode of action is similar to that of pills and their effective periods are much longer. Administration of progestogens or progestogen-estrogen combinations or IUDs within 72 hours of coitus have been found to be very effective as emergency contraceptives as they could be used to avoid possible pregnancy due to rape or casual unprotected intercourse. Surgical methods, also called sterilisation, are generally advised for the male/female partner as a terminal method to prevent any morepregnancies. Surgical intervention blocks gamete transport and thereby prevent conception. Sterilisation procedure in the male is called ‘vasectomy’ and that in the female, ‘tubectomy’. In vasectomy, a small part of the vas deferens is removed or tied up through a small incision on the scrotum whereas in tubectomy, a small part of the fallopian tube is removed or tied up through a small incision in the abdomen or through vagina. These techniques are highly effective but their reversibility is very poor.


Vasectomy	Tubectomy

It needs to be emphasised that the selection of a suitable contraceptive method and its use should always be undertaken in consultation with qualified medical professionals. One must also remember that contraceptives are not regular requirements for the maintenance of reproductive health. In fact, they are practiced against a natural reproductive event, i.e., conception/pregnancy. One is forced to use these methods either to prevent pregnancy or to delay or space pregnancy due to personal reasons. No doubt, the widespread use of these methods have a significant role in checking uncontrolled growth of population. However, their possible ill-effects like nausea, abdominal pain, breakthrough bleeding, irregular menstrual bleeding or even breast cancer, though not very significant, should not be totally ignored.

TISSUE CULTURE

2020-12-19T16:59:00.009+05:30

TISSUE CULTURE

As traditional breeding techniques failed to keep pace with demand and to provide sufficiently fast and efficient systems for crop improvement, another technology called tissue culture got developed. What does tissue culture mean? It was learnt by scientists, during 1950s, that whole plants could be regenerated from explants, i.e., any part of a plant taken out and grown in a test tube, under sterile conditions in special nutrient media. This capacity to generate a whole plant from any cell/explant is called totipotency. You will learn how to accomplish this in higher classes. It is important to stress here that the nutrient medium must provide a carbon source such as sucrose and also inorganic salts, vitamins, amino acids and growth regulators like auxins, cytokinins etc. By application of these methods it is possible to achieve propagation of a large number of plants in very short durations. This method of producing thousands of plants through tissue culture is called micropropagation. Each of these plants will be genetically identical to the original plant from which they were grown, i.e., they are somaclones. Many important food plants like tomato, banana, apple, etc.,

have been produced on commercial scale using this method. Try to visit a tissue culture laboratory with your teacher to better understand and appreciate the process. Another important application of the method is the recovery of healthy plants from diseased plants. Even if the plant is infected with a virus, the meristem (apical and axillary) is free of virus. Hence, one can remove the meristem and grow it in vitro to obtain virus-free plants. Scientists have succeeded in culturing meristems of banana, sugarcane, potato, etc. Scientists have even isolated single cells from plants and after digesting their cell walls have been able to isolate naked protoplasts (surrounded by plasma membranes). Isolated protoplasts from two different varieties of plants – each having a desirable character – can be fused to get hybrid protoplasts, which can be further grown to form a new plant. These hybrids are called somatic hybrids while the process is called somatic hybridisation. Imagine a situation when a protoplast of tomato is fused with that of potato, and then they are grown – to form new hybrid plants combining tomato and potato characteristics. Well, this has been achieved – resulting in formation of pomato; unfortunately this plant did not have all the desired combination of characteristics for its commercial utilisation.

Animal Breeding

2020-12-17T11:31:00.000+05:30

Animal Breeding

Breeding of animals is an important aspect of animal husbandry. Animal breeding aims at increasing the yield of animals and improving the desirable qualities of the produce. For what kind of characters would we breed animals? Would the selection of characters differ with the choice of animals?

What do we understand by the term ‘breed’? A group of animals related by descent and similar in most characters like general appearance, features, size, configuration, etc., are said to belong to a breed. Find out the names of some common breeds of cattle and poultry in the farms of your area.

When breeding is between animals of the same breed it is called inbreeding, while crosses between different breeds are called outbreeding.

Improved breed of

jersey cattle

Inbreeding :

Inbreeding refers to the mating of more closely related individuals within the same breed for 4- 6 generations. The breeding strategy is as follows – superior males and superior females of the same breed are identified and mated in pairs. The progeny obtained from such matings are evaluated and superior males and females among them are identified for further mating. A superior female, in the case of cattle, is the cow or buffalo that produces more milk per lactation. On the other hand, a superior male is the bull, which gives rise to superior progeny as compared to those of other males.

. A similar strategy is used for developing purelines in cattle as was used in case of peas. Inbreeding increases homozygosity. Thus inbreeding is necessary if we want to evolve a pureline in any animal. Inbreeding exposes harmful recessive genes that are eliminated by selection. It also helps in accumulation of superior genes and elimination of less desirable genes. Therefore, this approach, where there is selection at each step, increases the productivity of inbred population. However, continued inbreeding, especially close inbreeding, usually reduces fertility and even productivity. This is called inbreeding depression. Whenever this becomes a problem, selected animals of the breeding population should be matedwith unrelated superior animals of the same breed. This usually helps restore fertility and yield.

Out-breeding :

Out-breeding is the breeding of the unrelated animals, which may be between individuals of the same breed but having no common ancestors for 4-6 generations (out-crossing) or between different breeds (cross-breeding) or different species (inter-specific hybridisation).

Out-crossing:

This is the practice of mating of animals within the same breed, but having no common ancestors on either side of their pedigree up to 4-6 generations. The offspring of such a mating is known as an out-cross. It is the best breeding method for animals that are below average in productivity in milk production, growth rate in beef cattle, etc. A single outcross often helps to overcome inbreeding depression.

Cross-breeding:

In this method, superior males of one breed are mated with superior females of another breed. Cross-breeding allows the desirable qualities of two different breeds to be combined. The progeny hybrid animals may themselves be used for commercial production. Alternatively, they may be subjected to some form of inbreeding and selection to develop new stable breeds that may be superior to the existing breeds. Many new animal breeds have been developed by this approach. Hisardale is a new breed of sheep developed in Punjab by crossing Bikaneri ewes and Marino rams.

Interspecific hybridisation:

In this method, male and female animals of two different related species are mated. In some cases, the progeny may combine desirable features of both the parents, and may be of considerable economic value, e.g., the mule (Figure 9.2). Do you know what cross leads to the production of the mule?

Mule

Controlled breeding experiments are carried out using artificial insemination. The semen is collected from the male that is chosen as a parent and injected into the reproductive tract of the selected female by the breeder. The semen may be used immediately or can be frozen and used at a later date. It can also be transported in a frozen form to where the female is housed. In this way desirable matings are carried. Artificial insemination helps us overcome several problems of normal matings. Can you discuss and list some of them?

Often, the success rate of crossing mature male and female animals is fairly low even though artificial insemination is carried out. To improve chances of successful production of hybrids, other means are also used. Multiple Ovulation Embryo Transfer Technology (MOET) is one such programme for herd improvement. In this method, a cow is administered hormones, with FSH-like activity, to induce follicular maturation and super ovulation – instead of one egg, which they normally yield per cycle, theyproduce 6-8 eggs. The animal is either mated with an elite bull or artificially inseminated. The fertilised eggs at 8–32 cells stages, are recovered non-surgically and transferred to surrogate mothers. The genetic mother is available for another round of super ovulation. This technology has been demonstrated for cattle, sheep, rabbits, buffaloes, mares, etc. High milk-yielding breeds of females and high quality (lean meat with less lipid) meat-yielding bulls have been bred successfully to increase herd size in a short time.

Bee-keeping

Bee-keeping or apiculture is the maintenance of hives of honeybees for the production of honey. It has been an age-old cottage industry. Honey is a food of high nutritive value and also finds use in the indigenous systems of medicine. Honeybee also produces beeswax, which finds many uses in industry, such as in the preparation of cosmetics and polishes of various kinds. The increased demand of honey has led to large-scale beekeeping practices; it has become an established income generating industry, whether practiced on a small or on a large scale.

Bee-keeping can be practiced in any area where there are sufficient bee pastures of some wild shrubs, fruit orchards and cultivated crops. There are several species of honeybees which can be reared. Of these, the most common species is Apis indica. Beehives can be kept in one’s courtyard, on the verandah of the house or even on the roof. Bee-keeping is not labour-intensive.

Bee-keeping though relatively easy does require some specialised knowledge and there are several organisations that teach bee-keeping. The following points are important for successful bee-keeping:

(i) Knowledge of the nature and habits of bees,

(ii) Selection of suitable location for keeping the beehives,

(iii) Catching and hiving of swarms (group of bees),

(iv) Management of beehives during different seasons, and

(v) Handling and collection of honey and of beeswax. Bees are the pollinators of many of our crop species (see chapter 2) such as sunflower, Brassica, apple and pear. Keeping beehives in crop fields during flowering period increases pollination efficiency and improves the yield–beneficial both from the point of view of crop yield and honey yield.

Fisheries

Fishery is an industry devoted to the catching, processing or selling of fish, shellfish or other aquatic animals. A large number of our population is dependent on fish, fish products and other aquatic animals such as prawn, crab, lobster, edible oyster, etc., for food. Some of the freshwater fishes which are very common include Catla, Rohu and common carp. Some of the marine fishes that are eaten include – Hilsa, Sardines, Mackerel and Pomfrets. Find out what fishes are commonly eaten in your area.Fisheries has an important place in Indian economy. It provides income and employment to millions of fishermen and farmers, particularly in the coastal states. For many, it is the only source of their livelihood. In order to meet the increasing demands on fisheries, different techniques have been employed to increase production. For example, through aquaculture and pisciculture we have been able to increase the production of aquatic plants and animals, both fresh-water and marine. Find out the difference between pisciculture and aquaculture. This has led to the development and flourishing of the fishery industry, and it has brought a lot of income to the farmers in particular and the country in general. We now talk about ‘Blue Revolution’ as being implemented along the same lines as ‘Green Revolution’.

Animal husbandry

2020-12-16T22:05:00.000+05:30

With ever -increasing population of the world, enhancement of food production is a major necessity. Biological principles as applied to animal husbandry and plant breeding have a major role in our efforts to increase food production. Several new techniques like embryo transfer technology and tissue culture techniques are going to play a pivotal role in further enhancing food production.

Animal husbandry

Animal husbandry is the agricultural practice of breeding and raising livestock. As such it is a vital skill for farmers and is as much science as it is art. Animal husbandry deals with the care and breeding of livestock like buffaloes, cows, pigs, horses, cattle, sheep, camels, goats, etc., that are useful to humans. Extended, it includes poultry farming and fisheries. Fisheries include rearing, catching, selling, etc., of fish, molluscs (shell-fish) and crustaceans (prawns, crabs, etc.). Since time immemorial, animals like bees, silk-worm, prawns, crabs, fishes, birds, pigs, cattle, sheep and camels have been used by humans for products like milk, eggs, meat, wool, silk, honey, etc. It is estimated that more then 70 per cent of the world livestock population is in India and China. However, it issurprising to note that the contribution to the world farm produce is only 25 per cent, i.e., the productivity per unit is very low. Hence, in addition to conventional practices of animal breeding and care, newer technologies also have to be applied to achieve improvement in quality and productivity.

Management of Farms and Farm Animals

A professional approach to what have been traditional practices of farm management gives the much needed boost to our food production. Let us discuss some of the management procedures, employed in various animal farm systems.

Dairy Farm Management

Dairying is the management of animals for milk and its products for human consumption. Can you list the animals that you would expect to find in a dairy? What are different kinds of products that can be made with milk from a dairy farm? In dairy farm management, we deal with processes and systems that increase yield and improve quality of milk. Milk yield is primarily dependent on the quality of breeds in the farm. Selection of good breeds having high yielding potential (under the climatic conditions of the area), combined with resistance to diseases is very important. For the yield potential to be realised the cattle have to be well looked after – they have to be housed well, should have adequate water and be maintained disease free. The feeding of cattle should be carried out in a scientific manner – with special emphasis on the quality and quantity of fodder. Besides, stringent cleanliness and hygiene (both of the cattle and the handlers) are of paramount importance while milking, storage and transport of the milk and its products. Nowadays, of course, much of these processes have become mechanised, which reduces chance of direct contact of the produce with the handler. Ensuring these stringent measures would of course, require regular inspections, with proper record keeping. It would also help to identify and rectify the problems as early as possible. Regular visits by a veterinary doctor would be mandatory. You would probably find it interesting if you were to prepare a questionnaire on diverse aspects of dairy keeping and then follow it up with a visit to a dairy farm in your locality and seek answers to the questions.

Poultry Farm Management

Poultry is the class of domesticated fowl (birds) used for food or for their eggs. They typically include chicken and ducks, and sometimes turkey and geese. The word poultry is often used to refer to the meat of only these birds, but in a more general sense it may refer to the meat of other birds too. As in dairy farming, selection of disease free and suitable breeds, proper and safe farm conditions, proper feed and water, and hygiene and health care are important components of poultry farm managementYou may have seen TV news or read newspaper– reports about the ‘bird flu virus’ which created a scare in the country and drastically affected egg and chicken consumption. Find out more about it and discuss whether the panic reaction was justified. How can we prevent the spread of the flu in case some chicken are infected?

fact of space

2020-12-15T18:19:00.001+05:30

अंतरिक्ष में जाने के छह महीने बाद अंतरिक्ष यात्रियों का कद बढ़ जाता है। उनका कद उनकी वास्तविक ऊंचाई से तीन फीसदी अधिक हो जाता है। यह सब इसलिए होता है क्योंकि अंतरिक्ष में जाने के बाद उनपर पृथ्वी के गुरुत्वाकर्षण का कोई प्रभाव नहीं पड़ता। लेकिन ऐसा लंबे समय तक नहीं रहता। धरती पर आने के कुछ महीनों बाद उनका कद पहले की तरह ही सामान्य हो जाता है।

Recombinant DNA technology

2020-12-14T15:32:00.003+05:30

Recombinant DNA technology

Recombinant DNA technology (also known as genetic engineering) is the set of techniques that enable the DNA from different sources to be identified, isolated and recombined so that new characteristics can be introduced into an organism. The invention of recombinant DNA technology—the way in which genetic material from one organism is artificially introduced into the genome of another organism and then replicated and expressed by that other organism—was largely the work of Paul Berg, Herbert W. Boyer, and Stanley N. Cohen, although many other scientists made important contributions to the new technology as well. Paul Berg developed the first recombinant DNA molecules that combined DNA from SV40 virus and lambda phage. Later in 1973, Herbert Boyer and Stanley Cohen develop recombinant DNA technology, showing that genetically engineered DNA molecules may be cloned in foreign cells. One important aspect in recombinant DNA technology is DNA cloning. It is a set of techniques that are used to assemble recombinant DNA molecules and to direct their replication within host organisms. The use of the word cloning refers to the fact that the method involves the replication of a single DNA molecule starting from a single living cell to generate a large population of cells containing identical DNA molecules.

DNA cloning

DNA cloning is the production of a large number of identical DNA molecules from a single ancestral DNA molecule. The essential characteristic of DNA cloning is that the desired DNA fragments must be selectively amplified resulting in a large increase in copy number of selected DNA sequences. In practice, this involves multiple rounds of DNA replication catalyzed by a DNA polymerase acting on one or more types of template DNA molecule. Essentially two different DNA cloning approaches are used: Cell-based and cell-free DNA cloning.

Cell-based DNA cloning

This was the first form of DNA cloning to be developed, and is an in vivo cloning method. The first step in this approach involves attaching foreign DNA fragments in vitro to DNA sequences which are capable of independent replication. The recombinant DNA fragments are then transferred into suitable host cells where they can be propagated selectively. The essence of cell-based DNA cloning involves following steps:

Construction of recombinant DNA molecules

Recombinants are hybrid DNA molecules consisting of autonomously replicating DNA segment plus inserted elements. Such hybrid molecules are also called chimera. Recombinant DNA molecules are constructed by in vitro covalent attachment (ligation) of the desired DNA fragments (target DNA) to a replicon (any sequence capable of independent DNA replication). This step is facilitated by cutting the target DNA and replicon molecules with specific restriction endonucleases before joining the different DNA fragments using the enzyme DNA ligase.

Transformation

The recombinant DNA molecules are transferred into host cells (often bacterial or yeast cells) in which the chosen replicon can undergo DNA replication independently of the host cell chromosome(s).

Seltive propagation of cell clones

Selective propagation of cell clones involves two stages. Initially the transformed cells are plated out by spreading on an agar surface in order to encourage the growth of well-separated cell colonies. These are cell clones (populations of identical cells all descended from a single cell). Subsequently, individual colonies can be picked from the plate and the cells can be further expanded in liquid culture.

Isolation of recombinant DNA clones

Isolation of recombinant DNA clones by harvesting expanded cell cultures and selectively isolating the recombinant DNA.

Cell-free DNA cloning

The polymerase chain reaction (PCR) is a newer form of DNA cloning which is enzyme mediated and is conducted entirely in vitro. PCR (developed in 1983 by Kary Mullis) is a revolutionary technique used for selective amplification of specific target sequence of nucleic acid by using short primers. It is a rapid, inexpensive and simple method of copying specific DNA sequence.

Enzymes for DNA manipulation

The enzymes used in the recombinant DNA technology fall into four broad categories:

Template-dependent DNA polymerase

DNA polymerase enzymes that synthesize new polynucleotides complementary to an existing DNA or RNA template are included in this category. Different types of DNA polymerase are used in gene manipulation.

DNA polymerase I (Kornberg enzyme) has both the 3’-5’ and 5’-3’ exonuclease activities and 5’-3’ polymerase activity.

Reverse transcriptase, also known as RNA-directed DNA polymerase, synthesizes DNA from RNA.

Reverse transcriptase was discovered by Howard Temin at the University of Wisconsin, and independently by David Baltimore at about the same time. The two shared the 1975 Nobel Prize in Physiology or Medicine. Taq DNA polymerase is a DNA polymerase derived from a thermostable bacterium, Thermus aquaticus. It operates at 72°C and is reasonably stable above 90°C and used in PCR. It has a 5’ to 3’ polymerase activity and a 5’ to 3’ exonuclease activity, but it lacks a 3’ to 5’ exonuclease (proofreading) activity.

Nucleases

Nucleases are enzymes that degrade nucleic acids by breaking the phosphodiester bonds that link one nucleotide to the next. Ribonucleases (RNases) attack RNA and deoxyribonucleases (DNases) attack DNA. Some nucleases will only attack single stranded nucleic acids, others will only attack double-stranded nucleic acids and a few will attack either kind. Nuclease are of two different kinds – exonucleases and endonucleases. Exonucleases remove nucleotides one at a time from the end of a nucleic acid whereas endonucleases are able to break internal phosphodiester bonds within a nucleic acid. Any particular exonuclease attacks either the 3’-end or the 5’-end but not both.

Mung bean nuclease

The mung bean nuclease is an endonuclease specific for ssDNA and RNA. It is purified from mung bean sprouts. It digests single-stranded nucleic acids, but will leave intact any region which is double stranded. It requires Zn2+ for catalytic activity.

S1 nuclease

The S1 nuclease is an endonuclease purified from Aspergillus oryzae. This enzyme degrades RNA or single stranded DNA, but does not degrade dsDNA or RNA-DNA hybrids in native conformation. Thus, its activity is similar to mung bean nuclease, however, the enzyme will also cleave a strand opposite a nick on the complementary strand.

RNase

A RNase A is an endonuclease, which digests ssRNA at the 3’ end of pyrimidine residues.
RNase H
It is an endonuclease which digests the RNA strand of an RNA-DNA heteroduplex. The enzyme does not digest ss or dsDNA.
thermodynamically less stable than DNA because of the 2’ hydroxyl group on the ribose ring that promotes hydrophilic attack on the 5’-3’ phosphodiester bond to form a 2’-3’ cyclic phosphate. Therefore, even if all RNases are eliminated or inhibited during RNA purification, RNA spontaneously degrades while in solution. To circumvent this biological decay of RNA, purified samples are stored at –20°C as ethanol precipitates. The purification of mRNA involves two basic steps
: 1. Biochemical separation of total cellular RNA from DNA and protein using a strong protein denaturant to inhibit cellular RNases, and
2. Isolation of poly A tail mRNA using an oligo dT affinity matrix. A common method used to isolate mRNA from tissue culture cells is outlined in the following figure 2.4. Guanidinium thiocyanate is a protein denaturant that lyses the cells and inhibits cellular RNases.

life on Mars

2020-12-14T14:45:00.002+05:30

Scientists searching for life on Mars have achieved great success. Such fossils have been found in Australia which lived billions of years ago without oxygen. This will make the search for life in Mars much easier.

Micro fossils found in Australia have supported the fact that life on Mars is possible. These fossils found in Australia reveal that 3.4 billion years ago, there were bacteria in the earth that did not have oxygen and this has reinforced the hope that life exists on Mars.

Fossil specimens were found from the Streley Pool in the Pilbara area of Western Australia. Here after the micro-germ die, the crystals were secured between the particles. In the year 2002, another team of scientists working just 35 km away in the same area got bacterial fossils. But this claim was rejected by some scientists, saying that it is not the fossils of bacteria but the result of mineralization of stones. Researchers from Western Australia and Oxford University say that fossils of microscopic germs located in ancient sedimentary rocks are It has been confirmed that they are the oldest fossils found so far. There was a debate about this for almost a decade.

Signs of water

If water is present on Mars, then it is possible that bacteria also grow in it in summer. However these streams only appeared in summer and disappeared in cold weather. Scientists believe that these currents may have been made of mud and mud. Last day, NASA claimed that there were signs of water flowing on Mars. After this sign, the possibility of life on Mars has increased further. Scientists believe that the latest photographs taken from the hills of the planet Mars are the biggest proof of this. Long thick lines are seen in these pictures of Mars, which can actually be flowing currents. These streams are a few meters wide and are seen flowing on the plains surface passing through the stones.

ब्लैक होल क्या है?

2020-12-14T14:32:00.002+05:30

ब्लैक होल क्या है?

ब्लैक होल अंतरिक्ष में ऐसी जगह है जहां गुरुत्वाकर्षण इतना खींचता है कि प्रकाश भी नहीं बुझ सकता । गुरुत्वाकर्षण बहुत मजबूत है क्योंकि मामले को छोटी जगह में निचोड़ा गया है । यह तब हो सकता है जब एक सितारा मर रहा हो ।
क्योंकि कोई प्रकाश नहीं निकल सकता, लोगों को ब्लैक होल नहीं दिख रहा है । वे अदृश्य हैं । विशेष उपकरणों के साथ अंतरिक्ष दूरबीन काले छेद खोजने में मदद कर सकते हैं । विशेष उपकरण देख सकते हैं कि कैसे ब्लैक होल के बहुत करीब सितारे अन्य सितारों की तुलना में अलग तरीके से काम करते हैं ।

ब्लैक होल कितने बड़े हैं?

काले छेद बड़े या छोटे हो सकते हैं । वैज्ञानिकों को लगता है कि सबसे छोटे काले छेद सिर्फ एक परमाणु की तरह छोटे हैं । ये काले छेद बहुत छोटे हैं लेकिन बड़े पहाड़ का मास है । द्रव्यमान वस्तु में ′′ वस्तु ′′ या ′′ सामान ′′ की मात्रा है ।
एक अन्य प्रकार का ब्लैक होल ′′ स्टेलर ′′ कहा जाता है । इसका द्रव्यमान सूर्य के द्रव्यमान से 20 गुना अधिक हो सकता है । पृथ्वी की आकाशगंगा में कई, कई तारकीय बड़े काले छेद हो सकते हैं । पृथ्वी की आकाशगंगा को आकाशगंगा कहा जाता है ।
सबसे बड़े काले छेद को ′′ सुपरमैसिव ′′ कहा जाता है । इन काले छेदों में आम जनता है जो एक साथ 1 लाख से अधिक सूर्य हैं । वैज्ञानिकों ने सबूत पाया है कि हर बड़ी गैलेक्सी में अपने केंद्र में एक सुपरमैसिव ब्लैक होल होता है । आकाशगंगा आकाशगंगा के केंद्र में महाशय काले छेद को धनु A कहा जाता है । इसमें लगभग 4 लाख सूर्य के बराबर एक मास है और एक बहुत बड़ी गेंद के अंदर फिट होगा जो कुछ लाख पृथ्वी को पकड़ सकता है ।

ब्लैक होल कैसे बनते हैं?

वैज्ञानिकों को लगता है कि ब्रह्मांड शुरू होने पर सबसे छोटे काले छेद बने ।
तारकीय काले छेद तब बनते हैं जब एक बहुत बड़े सितारे का केंद्र अपने आप में गिर जाता है, या गिर जाता है । जब ऐसा होता है, तो सुपरनोवा का कारण बनता है । सुपरनोवा एक विस्फोटक सितारा है जो अंतरिक्ष में सितारे के हिस्से का विस्फोट करता है ।
वैज्ञानिकों को लगता है कि सुपरमैसिव ब्लैक छेद उसी समय किए गए थे जैसे वे आकाशगंगा में हैं ।

यदि काले छेद ′′ काले ′′ हैं, तो वैज्ञानिकों को कैसे पता चलता है कि वे वहां हैं?

एक ब्लैक होल नहीं देखा जा सकता क्योंकि मजबूत गुरुत्वाकर्षण सभी प्रकाश को ब्लैक होल के बीच में खींच लेता है । लेकिन वैज्ञानिक देख सकते हैं कि मजबूत गुरुत्वाकर्षण ब्लैक होल के आसपास के सितारों और गैस को कैसे प्रभावित करता है । वैज्ञानिक स्टार्स का अध्ययन कर सकते हैं ताकि पता चल सके कि वे चारों ओर उड़ रहे हैं, या परिक्रमा कर रहे हैं, एक ब्लैक होल ।
जब एक ब्लैक होल और एक तारा एक साथ पास होता है, तो हाई-एनर्जी लाइट बनती है । इस तरह की रोशनी को इंसान की आँखों से नहीं देखा जा सकता । वैज्ञानिक उच्च ऊर्जा प्रकाश को देखने के लिए अंतरिक्ष में उपग्रहों और दूरबीन का उपयोग करते हैं ।

क्या एक ब्लैक होल पृथ्वी को नष्ट कर सकता है?

सितारे, चाँद और ग्रहों को खाकर अंतरिक्ष में काले छेद नहीं घूमते । पृथ्वी एक ब्लैक होल में नहीं गिरेगी क्योंकि कोई ब्लैक होल पृथ्वी के लिए सौर प्रणाली के पर्याप्त करीब नहीं है ।
अगर सूर्य की जगह सूर्य की तरह एक काला छेद भी हो तो भी पृथ्वी नहीं गिरती । ब्लैक होल में सूर्य के समान गुरुत्वाकर्षण होगा । पृथ्वी और अन्य ग्रह काले छेद की परिक्रमा करेंगे क्योंकि वे अब सूर्य की परिक्रमा करते हैं ।
सूरज कभी ब्लैक होल में नहीं बदलेगा । सूरज इतना बड़ा सितारा नहीं है जो ब्लैक होल कर सके ।

नासा ब्लैक होल का अध्ययन कैसे कर रहा है?

नासा उन उपग्रहों और दूरबीनों का उपयोग कर रहा है जो ब्लैक होल के बारे में अधिक जानने के लिए अंतरिक्ष में यात्रा कर रहे हैं । ये अंतरिक्ष यान वैज्ञानिकों को ब्रह्मांड के सवालों के जवाब देने में मदद करते हैं ।

छवि: वैज्ञानिकों ने एक ब्लैक होल की पहली छवि प्राप्त की है, इवेंट क्षितिज दूरदर्शी अवलोकन का उपयोग करके आकाशगंगा एम 6.5 के केंद्र के गहन गुरुत्वाकर्षण में प्रकाश झुकने के रूप में एक उज्ज्वल अंगूठी दिखाता है जो 6.5 अरब गुना है सूर्य से अधिक भारी । 

Chromosomal basis of inheritance

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Chromosomal basis of inheritance

In 1902, Walter S. Sutton and T. Boveri proposed the chromosomal theory of heredity. The theory provides a way to explain how the cellular transmission or chromosomes passes genetic determinant (i.e. genes) from parent to offspring. According to this view:

1. Chromosome contains the genetic material (genes) that is transmitted from parent to offspring.

2. Chromosomes are replicated and passed along generation after generation from parent to offspring.

3. The nuclei of most eukaryotic cells contain chromosomes that are found in homologous pairs (i.e. they are diploid). One member of each pair is inherited from the mother, the other from the father. At meiosis, one of the two members of each pair segregates into one daughter nucleus and the other segregates into different daughter nucleus. Therefore, gametes contain one set of chromosomes (i.e. they are haploid) as shown in figure 1.6.

4. During gamete formation, different types of chromosomes segregate independently of each other.

5. Each parent contributes one set of chromosomes to its offspring.

Hence, the chromosome theory of inheritance describes the relationship between Mendel’s Law and chromosomal transmission.

Genetics

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All living organisms reproduce. Reproduction results in the formation of offspring of the same kind. However, the resulting offspring need not and, most often, does not totally resemble the parent. Several characteristics may differ between individuals belonging to the same species. These differences are termed variations. The mechanism of transmission of characters, resemblances as well as differences, from the parental generation to the offspring, is called heredity. The scientific study of heredity, variations and the environmental factors responsible for these, is known as genetics (from the Greek word genno = give birth). The word genetics was first suggested to describe the study of inheritance and the science of variation by prominent British scientist William Bateson. Genetics can be divided into three areas: classical genetics, molecular genetics and evolutionary genetics. In classical genetics, we are concerned with Mendel’s principles, sex determination, sex linkage and cytogenetics. Molecular genetics is the study of the genetic material: its structure, replication and expression, as well as the information revolution emanating from the discoveries of recombinant DNA techniques. Evolutionary genetics is the study of the mechanisms of evolutionary change or changes in gene frequencies in populations (population genetics).

Appearance and genetic makeup of garden pea plant flowers: Based on Mendel’s experiments, the genotype of the pea flowers could be determined from the phenotypes of the flowers.

1.1 Mendel’s principles

Gregor Johann Mendel (1822–1884), known as the Father of Genetics, was an Austrian monk. In 1856, he published the results of hybridization experiments titled Experiments on Plant Hybrids in a journal “The proceeding of the Brunn society of natural history” and postulated the principles of inheritance which are popularly known as Mendel’s laws. But his work was largely ignored by scientists at that time. In 1900, the work was independently rediscovered by three biologists - Hugo de Vries of Holland, Carl Correns of Germany and Erich Tschermak of Austria. Mendel did a statistical study (he had a mathematical background). He discovered that individual traits are inherited as discrete factors which retain their physical identity in a hybrid. Later, these factors came to be known as genes. The term was coined by Danish botanist Wilhelm Johannsen in 1909. A gene is defined as a unit of heredity that may influence the outcome of an organism’s traits. Mendel’s experiment Mendel chose the garden pea, Pisum sativum, for his experiments since it had the following advantages.

1. Well-defined discrete characters

2. Bisexual flowers

3. Predominant self fertilization

4. Easy hybridization

5. Easy to cultivate and relatively short life cycle

Genetics Characters studied by Mendel

The characteristics of an organism are described as characters or traits. Traits studied by Mendel were clear cut and discrete. Such clear-cut, discrete characteristics are known as Mendelian characters. Mendel studied seven characters/ traits (all having two variants) and these are:

Dominant Recessive

1. Stem length Tall Dwarf

2. Flower position Axial Terminal

3. Flower colour Violet White

Seed coat colour Grey White

4. Pod shape Inflated Constricted

5 pod colour greeen Yellow

6. Cotyledon colour Yellow Green

7. Seed form Round Wrinkled

Flower colour is positively correlated with seed coat colours. Seeds with white seed coats were produced by plants that had white flowers and those with gray seed coats came from plants that had violet flower.

Allele

Each gene may exist in alternative forms known as alleles, which code for different versions of a particular inherited character. We may also define alleles as genes occupying corresponding positions on homologous chromosomes and controlling the same characteristic (e.g. height of plant) but producing different effects (tall or short). The term homologous refers to chromosomes that carry the same set of genes in the same sequence, although they may not necessarily carry identical alleles of each gene.

Wild-type versus Mutant alleles

Prevalent alleles in a population are called wild-type alleles. These alleles typically encode proteins that are made in the right amount and function normally. Alleles that are present at less than 1% in the population and have been altered by mutation are called mutant alleles. Such alleles usually result in a reduction in the amount or function of the wild-type protein and are most often inherited in a recessive fashion.

Dominant and Recessive alleles

A dominant allele masks or hides expression of a recessive allele and it is represented by an uppercase letter. A recessive allele is an allele that exerts its effect only in the homozygous state and in heterozygous condition its expression is masked by a dominant allele. It is represented by a lowercase letter.

Homozygous and Heterozygous

Each parent (diploid) has two alleles for a trait — they may be:

1. Homozygous, indicating they possess two identical alleles for a trait. a. Homozygous dominant genotypes possess two dominant alleles for a trait (TT). b. Homozygous recessive genotypes possess two recessive alleles for a trait (tt).

2. Heterozygous genotypes possess one of each allele for a particular trait (Tt ]

Lethal alleles

Certain genes are absolutely essential for survival. The alleles created by mutations in these genes are called lethal alleles. The phenotypic manifestation of these alleles is the death of the organism. Lethal alleles may be recessive or dominant. Recessive lethal alleles are lethal when present in homozygous conditions whereas dominant lethal alleles show lethal effects even in heterozygous conditions. Dominant lethal alleles are very rare. Lethal alleles fall into four categories:

• Early onset : Lethal alleles which result in early death of an organism, during embryogenesis.

• Late onset : Lethal genes which have delayed effect so that the organism can live for some time but eventually succumb to the disease.

• Conditional : Lethal alleles which kill organism under certain environmental conditions only. For example, a temperature sensitive lethal allele may kill organism at high temperature, but not at low temperature.

• Semilethal : Lethal alleles which kill only some individuals in the population but not all.

Penetra ance and expressivity

The percentage of individuals that shows a particular phenotype among those capable of showing it, is known as penetrance. Let us take an example of polydactyly in human, which is produced by a dominant gene. Homozygous recessive genotype does not cause polydactyly. However, some heterozygous individuals are not polydactylous. If suppose 20% of heterozygous individuals do not show polydactyly, this means that the gene has a penetrance of 80%. Degree of expression of a trait is controlled by a gene. A particular gene may produce different degrees of expression in different individuals. This is known as expressivity. Different degrees of expression in different individuals may be due to variation in the allelic constitution of the rest of the genome or to environmental factors. Thus, the terms penetrance and expressivity quantify the modification of gene expression by varying environment and genetic background; they measure respectively the percentage of cases in which the gene is expressed and the level of expression.

Phenocopy A phenotype that is not genetically controlled but looks like a genetically controlled one is called phenocopy. It is an environmentally induced phenotype that resembles the phenotype determined by the genotype. An example of a phenocopy is Vitamin-D-resistant rickets. A dietary deficiency of vitamin D, for example, produces rickets that is virtually indistinguishable from genetically caused rickets.

Probability

The chance that an event will occur in the future is called the event’s probability. For example, if you flip a coin, the probability is 0.50, or 50%, that the head side will be showing when it lands. The probability depends on the number of possible outcomes. In this case, there are two possible outcomes (head and tail), which are equally likely. This allows us to predict that there is a 50% chance that a coin flip will produce head. The general formula for the probability is:

Probability = Number of times an event occurs

Total number of events

Phead = 1 head/(1 head + 1 tail) = 1/2 = 50%

A probability calculation allows us to predict the likelihood that an event will occur in the future. The accuracy of this prediction, however, depends to a great extent on the size of the sample.\

In genetic problems, we are often interested in the probability that a particular type of offspring will be produced. For example, when two heterozygous tall pea plants (Tt) are crossed, the phenotypic ratio of the offspring is 3 tall : 1 dwarf. This information can be used to calculate the probability for either type of offspring:

Probability = Number of individuals with a given phenotype

Total number of individuals

Ptall = 3 tall/(3 tall + 1 dwarf) = 3/4 = 0.75 = 75% and Pdwarf = 1 dwarf/(3 tall + 1 dwarf) = 1/4 = 0.25 = 25%

The probability of obtaining a tall plant is 75% and a dwarf plant 25%. When we add together the probabilities of all the possible outcomes (tall and dwarf), we should get a sum of 100% (here, 75% + 25% = 100%). There are two basic laws of probability that are used for genetic analysis. The first law, the multiplicative law (product rule) of probability, states that the chance of two or more independent events occurring together is the product of the probability of the events occurring separately. Independent events are events whose outcomes do not influence one another. This is also known as the and rule. The product rule can be used to predict the probability of independent events that occur in a particular order.

Example 1,

A Mendelian cross has been made between pea plants that are heterozygous for plant height (Tt). What is the probability that the offspring will be homozygous recessive (tt)?

We can find the answer by applying the product rule. First, the probability that an egg will receive a ‘t’ allele = 1/2 and a sperm will receive a ‘t’ allele = 1/2. The overall probability that two recessive alleles will unite, one from the egg and one from the sperm, simultaneously, at fertilization is: 1/2 × 1/2 = 1/4.

Example 2, A cross has been made between two plants of genotypes AabbCcDd and AaBbCcdd. What is the probability that the offspring will be of genotype aabbccdd?

If we assume that all the gene pairs assort independently, then we can do this calculation easily by using the product rule. The four different gene pairs are considered individually, as if four separate crosses, and then the appropriate probabilities are multiplied together to arrive at the answer. From Aa × Aa, one-fourth of the progeny will be aa; from bb × Bb, one-half of the progeny will be bb; from Cc × Cc, one-fourth of the progeny will be cc; and from Dd × dd, one-half of the progeny will be dd. Therefore, the overall probability of progeny of genotype aabbccdd will be 1/4 × 1/2 × 1/4 × 1/2 = 1/64.

The second law is the additive law (sum rule) of probability. It states that the probability that one of two or more mutually exclusive events will occur is equal to the sum of the individual probabilities of the events. This is also known as the either or rule. The sum rule can be used to predict the occurrence of mutually exclusive events. Mutually exclusive events are events in which the occurrence of one possibility excludes the occurrence of the other possibilities.

Example 1, In a Mendelian cross between pea plants that are heterozygous for flower colour (Rr), what is the probability of the offspring being a heterozygote? There are two ways in which a heterozygote may be produced: the dominant allele (R) may be in the egg and the recessive allele (r) in the sperm or the dominant allele may be in the sperm and the recessive in the egg. Consequently, the probability that the offspring will be heterozygous is the sum of the probabilities of those two possible ways: Probability that the dominant allele will be in the egg with the recessive in the sperm is 1/2 × 1/2 = 1/4. Probability that the dominant allele will be in the sperm and the recessive in the egg is 1/2 × 1/2 = 1/4. Therefore, the probability that a heterozygous offspring will be produced is 1/4 + 1/4 = 1/2.

Example 2, A heterozygous pea plant that is tall with yellow seeds, TtYy, is allowed to self-fertilize. What is the probability that an offspring will be either tall with yellow seeds, tall with green seeds, or dwarf with yellow seeds? The problem involves three mutually exclusive events, we can use the sum rule to solve it.

जन्तु ऊतक (animal tissue)

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जंतु ऊतक

ऊतक (tissue) किसी जीव के शरीर में कोशिकाओं के ऐसे समूह को कहते हैं जिनकी उत्पत्ति एक समान हो तथा वे एक विशेष कार्य करती हो। अधिकांशतः ऊतकों का आकार एवं आकृति एक समान होती है। परंतु कभी कभी कुछ उतकों के आकार एवं आकृति में असमानता पाई जाती है, मगर उनकी उत्पत्ति एवं कार्य समान ही होते हैं। कोशिकाएँ मिलकर ऊतक का निर्माण करती हैं। ऊतक में समान संरचना और कार्य होते हैं।^[1]

ऊतक के अध्ययन को ऊतक विज्ञानं (Histology) के रूप में जाना जाता है।

ऊतक दो प्रकार के होते हैं-

१. जन्तु ऊतक (Animal tissue) २. पादप ऊतक (Plant tissue)

परिधीय तंत्रिका की अनुप्रस्थ काट

जन्तु ऊतक (animal Tissue)

जन्तु ऊतक मुख्यत:पांच प्रकार के होते हैं:

उपकला या एपिथीलियमी ऊतक (epithelial tissue)
संयोजी ऊतक (connective tissues)
पेशी ऊतक (muscular tissues)
तंत्रिका ऊतक (nervous tissues)
जनन ऊतक

उपकला (Epithelial Tissue)

यह ऊतक शरीर को बाहर से ढँकता है तथा समस्त खोखले अंगों को भीतर से भी ढँकता है। रुधिरवाहिनियों के भीतर ऐसा ही ऊतक, जिसे अंत:स्तर कहते हैं, रहता है। उपकला का मुख्य कार्य रक्षण, शोषण एवं स्त्राव का है। उपकला के निम्न प्रकार हे -

(क) साधारण
(ख) स्तंभाकार
(ग) रोमश
(घ) स्तरित
(च) परिवर्तनशील
(छ) रंजककणकित

संयोजी ऊतक (Connective tissue)

यह ऊतक एक अंग को दूसरे अंग से जोड़ने का काम करता है। यह प्रत्येक अंग में पाया जाता है। इसके अंतर्गत

(क) रुधिर ऊतक,
(ख) अस्थि ऊतक,
(ग) लस ऊतक तथा
(घ) वसा ऊतक आते हैं।

रुधिर ऊतक के, लाल रुधिरकणिका तथा श्वेत रुधिरकणिका, दो भाग होते हैं। लाल रुधिरकणिका ऑक्सीजन का आदान प्रदान करती है तथा श्वेत रुधिरकणिका रोगों से शरीर की रक्षा करती है। मानव की लाल रुधिरकोशिका में न्यूक्लियस नहीं रहता है।

अस्थि ऊतक का निर्माण अस्थिकोशिका से, जो चूना एवं फ़ॉस्फ़ोरस से पूरित रहती है, होता है। इसकी गणना हम स्केलेरस ऊतक में करेंगे,

लस ऊतक लसकोशिकाओं से निर्मित है। इसी से लसपर्व तथा टॉन्सिल आदि निर्मित हैं। यह ऊतक शरीर का रक्षक है। आघात तथा उपसर्ग के तुरंत बाद लसपर्व शोथयुक्त हो जाते हैं।

वसा ऊतक दो प्रकार के होते हैं : एरिओलर तथा एडिपोस।

इनके अतिरिक्त (1) पीत इलैस्टिक ऊतक, (2) म्युकाइड ऊतक, (3) रंजक कणकित संयोजी ऊतक, (4) न्युराग्लिया आदि भी संयोजी ऊतक के कार्य, आकार, स्थान के अनुसार भेद हैं।

पेशी ऊतक (Muscular Tissue)

इसमें लाल पेशी तंतु रहते हैं, जो संकुचित होने की शक्ति रखते हैं। पेशी उत्तक भिन्न-भिन्न तन्तुओ से संचीत हुआ है, जिस में आन्तरीक-कोष अंतराल की कमी होती है।

रेखांकित या ऐच्छिक पेशी ऊतक वह है जो शरीर को सुक्ष्म प्रकार की गतियां कराता है, कंकाल पेशी का एकम ' कोष तंतु ' है। हर कोष तंतु पतला, लंबा और अनेक कोष-केन्द्रीत होता है। अगर उच्च कक्षा के जीवो का शरीर रचना विज्ञान (Animal Anatomy) परीक्षण कीया जाने पर वे गठरी (Bundles) में पाए जाते है।
अनैच्छिक या अरेखांकित पेशी ऊतक वह है जो आशयों की दीवार बनाता है तथा
हृत् पेशी (cardiac muscle) ऊतक रेखांकित तो है, परंतु ऐच्छिक नहीं है।

तंत्रिका ऊतक (Nervous Tissue)

इसमें संवेदनाग्रहण, चालन आदि के गुण होते हैं। इसमें तंत्रिका पेशियाँ तथा न्यूराग्लिया रहता है। मस्तिष्क के धूसर भाग में ये कोशिकाएँ रहती हैं तथा श्वेत भाग में न्यूराग्लिया रहता है। कोशिकाओं से ऐक्सोन तथा डेंड्रॉन नाक प्रर्वध निकलते हैं। नाना प्रकार के ऊतक मिलकर शरीर के विभिन्न अंगों (organs) का निर्माण करते हैं। एक प्रकार के कार्य करनेवाले विभिन्न अंग मिलकर एक तंत्र (system) का निर्माण करते हैं।

स्केलेरस ऊतक

यह संयोजी तंतु के समान होता है तथा शरीर का ढाँचा बनाता है। इसके अंतर्गत अस्थि तथा कार्टिलेज आते हैं। कार्टिलेज भी तीन प्रकार के होते हैं :

हाइलाइन,
फाइब्रो-कार्टिलेज, तथा
इलैस्टिक फाइब्रो-कार्टिलेज या पीत कार्टिलेज।

मानव शरीर में २०६ अस्थिया होती है

cell organ {कोशिकांग}

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क कोशिकांग

1 . माइटोकांड्रिया - केवल यूकैरिओट कोशिकाओं मैं पाया जाता है

- खोज-कोलिकर परन्तु श्रेय -अल्तमान को जाता है
- नामकरण -सी बेंदा ने यह एक दोहरी झिल्ली युक्त कोशिकांग है
- आंतरिक झिल्ली की गुहां मई अंगुलीनुमा वालन निकले रहते है जिन्हे क्रिस्टी कहते है
- क्रिस्टी के मध्य मैट्रिक्स पाया जाता है माइटोकांड्रिया मैं 70 s रिबोसोम पाया जाता है

2 प्लास्टिड [लवक]- ये पादप कोशिकाओं मैं होते है जैसे -हरित लवक , वर्णिलावक ,अवर्णिलावक

-प्रकाश संस्लेशन के दौरान कार्बोहइड्रेट का निर्माण करते है

- यह दोहरी झिल्ली युक्त कोशिकांग है अंत झिल्ली से घिरे भगत को स्ट्रोमा कहते है स्ट्रोमा

मैं एक जटिल तंत्र होता है जिसे थयेलकोईड कहते है

-सिक्के के चट्टे के समान सरचना को ग्रेना कहते है दो ग्रेना को जोड़ने वाली थाइलेकोईड अन्तर ग्रेनं कहलाती है

- स्ट्रोमा मैं डीनए , रिबोसोम, च्लोरोफिल वर्णक पाया जाता है

3 लाइसोसोम=> क्रिश्चियन डी डूवे ने सर्वप्रथम सन् 1955 में लाइसोसोम की खोज की। ये गोलाकार काय होते हैं, जिनके व्यास 0.4u-0.8u तक होता है। ये इकहरी युनिट मेम्ब्रेन से बने होते हैं तथा इनके अन्दर सघन मैट्रिक्स भरा रहता है, जिसमें ऐसिड फास्फेटेज एन्जाइम भरे रहते हैं।

1.न्यूक्लियेजेस - ये नाभिकीय अम्लों का नाइट्रोजनी क्षार , फास्फेट तथा शर्करा में जल - अपघटन करते हैं।

2. फास्फेटेजेस - ये फास्फेट यौगिकों का जल - अपघटन करते हैं।

3. प्रोटियेजेस - ये प्रोटीन्स का अमीनो का अम्लों में जल अपघटन करते हैं।

4. ग्लाइकोसाइडेजेस - ये जटिल कार्बोहाइड्रेट्स का मोनोसैकेराइड्स में जल अपघटन करते हैं।

5. सल्फेटेजेस - ये सल्फेट यौगिकों का जल अपघटन करते हैं।

6. लाइपेजेस - ये लिपिड अणुओं का ग्लिसरॉल तथा वसीय अम्लों में जल अपघटन करते हैं। 7.लाइसोसोम के फटने के साथ ही कोशिका विभाजन का प्रक्रम आरम्भ हो जाता है।

एक आदर्श जन्तु कोशिका के कोशिकाद्रव्य में विभिन्न कोशिकांगो का चित्र - (1) केन्द्रिका (2) केंद्रक (3) राइबोसोम (छोटे विन्दु) (4) आशय (vesicle) (5) रूखड़ा आंतरद्रव्यजालिका (6) गॉल्जीकाय (जलकाय) (7) कोशिकापंजर (8) साफ़ आंतरद्रव्यजालिका (9) सूत्रकणिका (10) रसधानी (11) कोशिकाद्रव्य (12) लयनकाय (13) तारक केन्द्र (centriole)

4 आन्तरद्रव्य जालिका या अंतःप्रद्रव्यजालिका (Endoplasmic reticulum)

सुकेन्द्रिक कोशिकाओं में एक झिल्लीदार कोशिकांग है। इस की झिल्ली केन्द्रक की झिल्ली से निकलती है। अंग्रेज़ी में अन्तर्दविक जालिका को एॆन्डोप्लाज़मिक रॆटिकुलम कहा जाता है। कोशिका में इस के दो प्रकार होतें हैं। एक प्रकार (रफ़) पर राइबोसोम जुड़े होतें हैं जहां प्रोटीन संश्लेषण होता है और दूसरा प्रकार (स्मूद) राइबोसोम रहित होता है। अन्तर्द्रविक जालिका पर संश्लेषित किए प्रोटीन कोशिका के बाहर भेजने के लिए होते हैं।

5 राइबोसोम सजीव कोशिका के कोशिका द्रव में स्थित बहुत ही सूक्ष्म कण हैं, जिनकी प्रोटीनों के संश्लेषण में महत्त्वपूर्ण भूमिका है। ये आनुवांशिक पदार्थों (डीएनए या आरएनए) के संकेतों को प्रोटीन शृंखला में परिवर्तित करते हैं ये एण्डोप्लाज्मिक रेटिकुलम के ऊपरी सतह पर पाये जाते हैं, इसके अलावा ये माइटोकाण्ड्रिया तथा क्लोरोप्लास्ट में भी पाये जाते हैं। राइबोसोम एक संदेशधारक राईबोस न्यूक्लिक अम्ल (एमआरएनए) के साथ जुड़े रहता है जिसमें किसी विशेष प्रोटीन के निर्माण के लिए आवश्यक अमीनो अम्ल को सही क्रमानुसार लगाने का संदेश रहता है। अमीनो अम्ल संदेशवाहक आरएनए अणुओं के साथ संलग्न रहते हैं। इस प्रकार राइबोसोम प्रोटीन के संश्लेषण में तो सहायता करता ही है लिपिड के उपापचयी क्रियाओं में भी सहायता करता है।

राइबोसोम की खोज 1955 के दशक में रोमानिया के जीववैज्ञानिक जॉर्ज पेलेड ने की थी। उन्होंने इस खोज के लिए इलैक्ट्रॉन सूक्ष्मदर्शी का प्रयोग किया था जिसके लिए उन्हें नोबेल पुरस्कार से सम्मानित किया गया था। राइबोसोम नाम १९५८ में वैज्ञानिक रिचर्ड बी. रॉबर्ट्स ने प्रस्तावित किया था। राइबोसोम और उसके सहयोगी अणु २०वीं शताब्दी के मध्य से जीवविज्ञान के क्षेत्र में अपनी पहचान बनाए हुए हैं। उन पर काफी शोध और अनुसंधान भी प्रगति पर हैं। राइबोसोम की दो उप-इकाइयां होती हैं जो एकसाथ मिलकर प्रोटीन के निर्माण में कार्यरत रहती हैं। इन दोनों उप-इकाईयों का आकार एवं गठन प्रोकैरियोटिक एवं यूकैरियोटिक कोशिकाओं में भिन्न-भिन्न होता है। को भारतीय मूल के वैज्ञानिक वेंकटरमन रामकृष्णन को रसायन विज्ञान के क्षेत्र में नोबेल पुरस्कार से सम्मानित किया गया था।उन्हें राइबोसोम की कार्यप्रणाली व संरचना के उत्कृष्ट अध्ययन के लिए यह पुरस्कार संयुक्त रूप से दिया गया।उनके इस शोध-कार्य से कारगर प्रतिजैविकों को विकसित करने में मदद मिलेगी। इसराइली महिला वैज्ञानिक अदा योनोथ और अमरीका के थॉमस स्टीज़ को भी संयुक्त रूप से इस सम्मान के लिए चुना गया।

6 केन्द्रक

कोशिका विज्ञान में केन्द्रक (लातीनी व अंग्रेज़ी: nucleus, न्यूक्लियस) वनस्पतियों, प्राणियों और सुकेन्द्रिक जीवों की अधिकांश कोशिकाओं में दोहरी झिल्ली द्वारा बंद एक भाग (या कोशिकांग) होता है। सुकेन्द्रिक जीवों की हर कोशिका में अधिकतर एक केन्द्रक होता है, लेकिन स्तनधारियों की लाल रक्त कोशिकाओं में कोई केन्द्रक नहीं होता और ओस्टियोक्लास्ट कोशिकाओं में कई केन्द्रक होते हैं। प्राणियों के केन्द्रकों का व्यास लगभग ६ माइक्रोमीटर होता है और यह उनकी कोशिकाओं का सबसे बड़ा कोशिकांग होता है।

कोशिका केन्द्रकों में कोशिकाओं की अधिकांश आनुवंशिक सामग्री होती है, जो कई लम्बे डी॰ ऍन॰ ए॰ अणुओं में सम्मिलित होती है, जिनके रेशों कई प्रोटीनों के प्रयोग से गुण सूत्रों (क्रोमोज़ोमों) में संगठित होते हैं। इन गुण सूत्रों में उपस्थित जीन कोशिका का जीनोम होते हैं और कोशिका की प्रक्रियाओं को संचालित करते हैं। केन्द्रक इन जीनों को सुरक्षित रखता है और जीन व्यवहार संचालित करता है, यानि केन्द्रक कोशिका का नियंत्रणकक्ष होता है। पूरा केन्द्रक एक लिपिड द्विपरत की बनी झिल्ली द्वारा घिरा होता है जो केन्द्रक झिल्ली (nuclear membrane) कहलाती है और जो केन्द्रक के अन्दर की सामग्री को कोशिकाद्रव्य से पृथक रखता है। केन्द्रक के भीतर केन्द्रक आव्यूह (nuclear matrix) कहलाने वाला रेशों का ढांचा होता है जो केन्द्रक को आकार बनाए रखने के लिए यांत्रिक सहारा देता है, ठीक उसी तरह जैसे कोशिका कंकाल पूरी कोशिका को यांत्रिक सहारा देता है।

7 तारक केन्द्र

कोशिका जीवविज्ञान में, तारक केन्द्र (centriole/ सेंट्रिओल) एक बेलनाकार कोशिकांग है जो मुख्यतः ट्युबिलिन (tubulin) नामक प्रोटीन से बना होता है। khoj-wan benden

तंत्रिका कोशिका को छोड़कर प्रायः सभी प्रकार के प्राणिकोशिका में केन्द्रक के समीप साइटोप्लाज्म में एक तारानुमा रचना दिखाई देती है जिसे तारककाय (centrosome) कहते हैं। तारककाय के दो प्रमुख भाग होते हैं, एक को सेन्ट्रिओल और दूसरे को सेन्ट्रोस्फीयर कहते हैं। तारककाय के मध्य में सेन्ट्रिओल दो स्वच्छ, घनीभूत कणिकाओं के रूप में दिखाई देते हैं। सेन्ट्रिओल को घेरकर जो गाढ़ा कोशिकाद्रव्य रहता है, उसे सेन्ट्रोस्फीयर कहा जाता है। यह कोशिका विभाजन में मदद करता है, सीलिया तथा कशाभिका का निर्माण कराता है तथा शुक्राणुओं की पूँछ का निर्माण कराता है।1888 में टी बोबेरी ने खोजा था।

कोशिका [cell]कोशिका जैविकी'

2020-12-10T16:07:00.007+05:30

कोशिका (Cell) सजीवों के शरीर की रचनात्मक और क्रियात्मक इकाई है और प्राय: स्वत: जनन की सामर्थ्य रखती है। यह विभिन्न पदार्थों का वह छोटे-से-छोटा संगठित रूप है जिसमें वे सभी क्रियाएँ होती हैं जिन्हें सामूहिक रूप से हम जीवन कहतें हैं।
सजीवों की सभी जैविक क्रियाएँ कोशिकाओं के भीतर होती हैं। कोशिकाओं के भीतर ही आवश्यक आनुवांशिक सूचनाएँ होती हैं जिनसे कोशिका के कार्यों का नियंत्रण होता है तथा सूचनाएँ अगली पीढ़ी की कोशिकाओं में स्थानान्तरित होती हैं।^[2]

कोशिकाओं का विधिवत अध्ययन कोशिका विज्ञान (Cytology) या कोशिका जैविकी'' (Cell Biology) कहलाता है।

आविष्कार एवं अनुसंधान का इतिहास

रॉबर्ट हुक ने 1665 में बोतल की कार्क की एक पतली परत के अध्ययन के आधार पर मधुमक्खी के छत्ते जैसे कोष्ठ देखे और इन्हें कोशा नाम दिया। यह तथ्य उनकी पुस्तक माइक्रोग्राफ़िया में छपा। राबर्ट हुक ने कोशा-भित्तियों के आधार पर कोशा शब्द प्रयोग किया।

1674 एंटोनी वॉन ल्यूवेन्हॉक ने जीवित कोशा का सर्वप्रथम अध्ययन किया।

उन्होंने जीवित कोशिका को दाँत की खुरचनी में देखा था ।

1831 में रॉबर्ट ब्राउन ने कोशिका में 'केंद्रक एवं केंद्रिका' का पता लगाया।

तदरोचित नामक वैज्ञानिक ने 1824 में कोशिका सिद्धांत (cell theory) का विचार प्रस्तुत किया, परन्तु इसका श्रेय वनस्पति-विज्ञान-शास्त्री श्लाइडेन (Matthias Jakob Schleiden) और जन्तु-विज्ञान-शास्त्री श्वान (Theodor Schwann) को दिया जाता है जिन्होंने ठीक प्रकार से कोशिका सिद्धांत को (1839 में) प्रस्तुत किया और बतलाया कि 'कोशिकाएं पौधों तथा जन्तुओं की रचनात्मक इकाई हैं।'

1855 : रुडॉल्फ विर्चो ने विचार रखा कि कोशिकाएँ सदा कोशिकाओं के विभाजन से ही पैदा होती हैं।

1953: वाट्सन और क्रिक (Watson and Crick) ने डीएनए के 'डबल-हेलिक्स संरचना' की पहली बार घोषणा की।

1981: लिन मार्गुलिस (Lynn Margulis) ने कोशिका क्रम विकास में 'सिबियोस' (Symbiosis in Cell Evolution) पर शोधपत्र प्रस्तुत किया।

1888: में वाल्डेयर (Waldeyer) ने गुणसूत्र (Chromosome) का नामकरण किया ।

1883: ईमें स्विम्पर (ने पर्णहरित (Chloroplast) Schimper) का नामकरण किया ।

1892: में वीजमैन (Weissman) ने सोमेटोप्लाज़्म (Somatoplasm) एवं जर्मप्लाज्म (Germplasm) के बीच अंतर स्पष्ट किया।

1955: में जी.इ पैलेड (G.E. Palade) ने राइबोसोम (Ribosome) की खोज की। ^[3]

प्रकार

दो प्रकार की कोशिकाएँ : यूकैरोटिक (बाएँ) तथा प्रोकैरिओटिक (दाएँ)

कोशिकाएँ दो प्रकार की होती हैं,

प्रोकैरियोटिक कोशिका (prokaryotic cells) तथा
यूकैरियोटिक कोशिका (eukaryotic cell)

प्रोकैरियोटिक कोशिकाएँ प्रायः स्वतंत्र होती हैं जबकि यूकैरियोटिक कोशिकाएँ, बहुकोशीय प्राणियों में पायी जाती हैं। प्रोकैरियोटिक कोशिका में कोई स्पष्ट केन्द्रक नहीं होता है। इनमें पाए जाने वाले अल्पविकसित केन्द्रक को केंद्रकाभ कहते है जो कोशिका द्रव में बिखरे होते हैं। इस प्रकार की कोशिका जीवाणु तथा नीली हरी शैवाल में पायी जाती है। सभी उच्च श्रेणी के पौधों और जन्तुओं में यूकैरियोटिक प्रकार की कोशिका पाई जाती है। सभी यूकैरियोटिक कोशिकाओ में संगठित केन्द्रक पाया जाता है जो एक आवरण से ढका होता है।

कोशिका संरचना

कोशिकाएँ सजीव होती हैं तथा वे सभी कार्य करती हैं, जिन्हें सजीव प्राणी करते हैं। इनका आकार अतिसूक्ष्म तथा आकृति गोलाकार, अंडाकार, स्तंभाकार, रोमकयुक्त, कशाभिकायुक्त, बहुभुजीय आदि प्रकार की होती है। ये जेली जैसी एक वस्तु द्वारा घिरी होती हैं। इस आवरण को कोशिकावरण (cell membrane) या कोशिका-झिल्ली कहते हैं यह झिल्ली अवकलीय पारगम्य (selectively permeable) होती है जिसका अर्थ है कि यह झिल्ली किसी पदार्थ (अणु या ऑयन) को मुक्त रूप से पार होने देती है, सीमित मात्रा में पार होने देती है या बिल्कुल रोक देती है। इसे कभी-कभी 'जीवद्रव्य कला' (plasma membrane) भी कहा जाता है। इसके भीतर निम्नलिखित संरचनाएँ पाई जाती हैं:-

(1) केंद्रक एवं केंद्रिका

(2) जीवद्रव्य

(3) गोल्गी सम्मिश्र या गोल्गी यंत्र

(4) कणाभ सूत्र

(5) अंतर्प्रद्रव्य डालिका

(6) गुणसूत्र (पितृसूत्र) एवं जीन

(7) राइबोसोम तथा सेन्ट्रोसोम

(8) लवक

कुछ खास भिन्नताओं को छोड़ सभी प्रकार की कोशिकाओं, पादप एवं जन्तु कोशिका की संरचना लगभग एक जैसी होती है। ये सजीव और निर्जीव दोनों तरह की इकाईयों से मिलकर बनी होती हैं। एक सामान्य कोशिका या प्रारूपिक कोशिका के मुख्य तीन भाग हैं, कोशिकावरण, कोशिका द्रव्य एवं केन्द्रक। कोशिकावरण कोशिका का सबसे बाहर का आवरण या घेरा है। पादप कोशिका में कोशिका भित्ति और कोशिका झिल्ली मिलकर कोशिकावरण का निर्माण करते हैं। जन्तु कोशिका में कोशिका भित्ति नहीं पाई जाती अतः कोशिका झिल्ली ही सबसे बाहरी आवरण है। कोशिका झिल्ली एवं केन्द्रक के बीच के भाग को कोशिका द्रव्य कहा जाता है, इसमें विभिन्न कोशिकांग होते हैं। केन्द्रक कोशिका के अन्दर पाये जाने वाली एक गोल एवं सघन रचना है। केन्द्रक को कोशिका का 'मस्तिष्क' कहा जाता है। जिस प्रकार शरीर के सारे क्रियायों का नियंत्रण मस्तिष्क करता है ठीक उसी प्रकार कोशिका के सारे कार्यों का नियंत्रण केन्द्रक द्वारा होता है।

केंद्रक

एक कोशिका में सामान्यतः एक ही केंद्रक (nucleus) होता है, किंतु कभी-कभी एक से अधिक केंद्रक भी पाए जाते हैं। कोशिका के समस्त कार्यों का यह संचालन केंद्र होता है। जब कोशिका विभाजित होती है तो इसका भी विभाजन हो जाता है। केंद्रक कोशिका के भीतर एक तरल पदार्थ कोशिकाद्रव्य (cytoplasm) में प्राय: तैरता रहता है। इसका यद्यपि कोई निश्चित स्थान नहीं होता, तथापि यह अधिकतर लगभग मध्यभाग में ही स्थित होता है। कुछ कोशिकाओं में इसकी स्थिति आधारीय (basal) और कुछ में सीमांतीय (peripheral) भी होती है। केंद्रक की आकृति गोलाकार, वर्तुलाकार या अंडाकार होती है। तथापि, कभी-कभी यह बेलनाकार, दीर्घवृत्ताकार, सपात, शाखान्वित, नाशपाती जैसा, भालाकार आदि स्वरूपों का भी हो सकता है। इसके भीतर केंद्रकरस (nuclear sap) केंद्रिका (nucleolus) तथा पितृसूत्र (chromosomes) पाए जाते हैं। केंद्रक के आवरण को केंद्रककला (nuclear membrance or nucleolemma) कहते हैं।

केंद्रिका (Nucleolus)

प्रत्येक केंद्रक में एक या अधिक केंद्रिकाएँ पाई जाती हैं। कोशिका विभाजन की कुछ विशेष अवस्था में केंद्रिका लुप्त हो जाती, किंतु बाद में पुन: प्रकट हो जाती है। केंद्रिका के भीतर रिबोन्यूक्लीइक अम्ल (ritioncleric acid or RNA) तथा कुछ विशेष प्रकार के एंज़ाइम अधिक मात्रा में पाए जाते हैं। केंद्रिका सूत्रण (mitosis) या सूत्री विभाजन में महत्वपूर्ण भूमिका अदा करते हैं।

जीवद्रव्य (protoplasm)

यह एक गाढ़ा तरल पदार्थ होता है जो स्थानविशेष पर विशेष नामों द्वारा जाना जाता है; जैसे, द्रव्यकला (plasma membrane) तथा केंद्रक के मध्यवर्ती स्थान में पाए जाने वाले जीवद्रव्य को कोशिकाद्रव्य (cyt plasm) और केंद्रक झिल्ली (nuclear membrane) के भीतर पाए जाने वाले जीवद्रव्य को केंद्रक द्रव्य (nucleoplasm) कहते हैं। कोशिका का यह भाग अत्यंत चैतन्य और कोशिका की समस्त जैवीय प्रक्रियाओं का केंद्र होता है। इसे इसीलिए 'सजीव' (living) कहा जाता है। जीव वैज्ञानिक इसे 'जीवन का भौतिक आधार' (physcial basis of life) नाम से संबोधित करते हैं। आधुनिक जीव वैज्ञानिकों ने जीवद्रव्य का रासायनिक विश्लेषण करके यह तो पता लगा लिया है कि उसका निर्माण किन-किन घटकों द्वारा हुआ है, किंतु आज तक किसी भी वैज्ञानिक को उसमें (जीवद्रव्य) प्राण का संचार करने में सफलता हाथ नहीं लगी है। ऐसा है यह प्रकृति का रहस्यमय पदार्थ।

जीवद्रव्य का निर्माण कार्बन, हाइड्रोजन, ऑक्सीजन तथा अनेक कार्बनिक (organic) तथा अकार्बनिक (inorganic) पदार्थो द्वारा हुआ होता है। इसमें जल की मात्रा लगभग 80% प्रोटीन 15%, वसाएँ 3% तथा कार्बोहाइड्रेट 1% और अकार्बनिक लवण की 1 होती है। जीवद्रव्यों के कई प्रकार होते हैं, जैसे कोलाइड (colloid), कणाभ (granular), तंतुमय (fibrillar), जालीदार (reticular), कूपिकाकार (alveolar), आदि।

गोल्गी सम्मिश्र या यंत्र (Golgi complex or apparatus)

इस अंग का यह नाम इसके खोजकर्ता कैमिलो गोल्गी, के नाम पर पड़ा है, जिन्होंने 1898 में सर्वप्रथम इसकी खोज की। यह अंग साधारणतः केंद्रक के समीप, अकेले या समूहों में पाया जाता है। इसकी रचना तीन तत्वों (elements) या घटकों (components) द्वारा हुई होती है : सपाट कोश (flattened sacs), बड़ी बड़ी रिक्तिकाएँ (large vacueles) तथा आशय (vesicles)। यह एक प्रकार के जाल (network) जैसा दिखलाई देता है। इनका मुख्य कार्य कोशिकीय स्रवण (cellular secretion) और प्रोटीनों, वसाओं तथा कतिपय किण्वों (enzymes) का भडारण करना (storage) है।

कणाभसूत्र (Mitochondria)

ये कणिकाओं (granules) या शलाकाओं (rods) की आकृतिवाले होते हैं। ये अंगक (organelle) कोशिकाद्रव्य (cytoplasm) में स्थित होते हैं। इनकी संख्या विभिन्न जंतुओं में पाँच लाख तक हो सकती है। इनका आकार 1/2 माइक्रॉन से लेकर 2 माइक्रॉन के बीच होता है। विरल उदाहरणों (rare cases) में इनकी लंबाई 40 माइक्रॉन तक हो सकती है। इनके अनेक कार्य बतलाए गए हैं, जो इनकी आकृति पर निर्भर करते हैं। तथापि इनका मुख्य कार्य कोशिकीय श्वसन (cellular respiration) बतलाया जाता है। इन्हें कोशिका का 'पावर प्लांट' (power plant) कहा जाता है, क्योंकि इनसे आवश्यक ऊर्जा (energy) की आपूर्ति होती रहती है।

अंतर्प्रद्रव्य जालिका (fndoplasmic reticulum)

यह जालिका कोशिकाद्रव्य (cytoplasm) में आशयों (vesicles) और नलिकाओं (tubules) के रूप में फैली रहती है। इसकी स्थिति सामान्यतः केंद्रकीय झिल्ली (nuclear membrane) तथा द्रव्यकला (plasma membrane) के बीच होती है, किंतु यह अक्सर संपूर्ण कोशिका में फैली रहती है। यह जालिका दो प्रकार की होती है : चिकनी सतहवाली (smooth surfaced) और खुरदुरी सतहवाली (rough surfaced)। इसकी सतह खुरदुरी इसलिए होती है कि इस पर राइबोसोम (ribosomes) के कण बिखरे रहते हैं। इसके अनके कार्य बतलाए गए हैं, जैसे यांत्रिक आधारण (mechanical support), द्रव्यों का प्रत्यावर्तन (exchange of materials), अंत: कोशिकीय अभिगमन (intracellular transport), प्रोटोन संश्लेषण (protein synthesis) इत्यादि।

गुणसूत्र या पितृसूत्र (chromosomes)

यह शब्द क्रोम (chrom ) तथा सोमा (soma ) शब्दों से मिलकर बना है, जिसका अर्थ होता है : रंगीन पिंड (colour bodies)। गुणसूत्र केंद्रकों के भीतर जोड़ों (pairs) में पाए जाते हैं और कोशिका विभाजन के साथ केंद्रक सहित बाँट जाया करते हैं। इनमें स्थित जीवों की पूर्वजों के पैत्रिक गुणों का वाहक कहा जाता है। इनकी संख्या जीवों में निश्चित होती है, जो एक दो जोड़ों से लेकर कई सौ जोड़ों तक हो सकती है। इनका आकार 1 माइक्रॉन से 30 तक (लंबा) होता है। इनकी आकृति साधारणतः अंग्रेजी भाषा के अक्षर S जैसी होती हैं। इनमें न्यूक्लिओ-प्रोटीन (nucle-o-protein) मुख्य रूप से पाए जाते हैं। पितृसूत्रों के कुछ विशेष प्रकार भी पाए जाते हैं, जिन्हें लैंपब्रश पितृसूत्र (lanmpbrush chromosomes) और पोलीटेने क्रोमोसोम (polyteene chromosomes) की संज्ञा दी गई है। इन्हें W, X, Y, Z, आदि नामों से संबोधित किया जाता है।

जीनों (gene)

जीनों को पैत्रिक गुणों का वाहक (carriers of hereditary characters) माना जाता है। क्रोमोसोम या पितृसूत्रों का निर्माण हिस्टोन प्रोटीन तथा डिऑक्सीराइबोन्यूक्लिक ऐसिड DNA तथा राइबोन्यूक्लिक ऐसिड RNA से मिलकर हुआ होता है। जीन का निर्माण इन्हीं में से एक, डी॰ एन॰ ए॰ द्वारा होता है। कोशिका विभाजनों के फलस्वरूप जब नए जीव के जीवन का सूत्रपात होता है, तो यही जीन पैतृक एवं शरीरिक गुणों के साथ माता पिता से निकलकर संततियों में चले जाते हैं। यह आदान प्रदान माता के डिंब (ovum) तथा पिता के शुक्राणु (sperms) में स्थित जीनों के द्वारा संपन्न होता है। सन्‌ 1970 के जून मास में अमरीका स्थित भारतीय वैज्ञानिक श्री हरगोविंद खुराना को कृत्रिम जीन उत्पन्न करने में अभूतपूर्व सफलता मिली थी। इन्हें सन्‌ 1978 में नोबेल पुरस्कार मिला था।

रिबोसोम (ribosomes) सेंट्रोसोम (centrosomes)

सूक्ष्म गुलिकाओं के रूप में प्राप्त इन संरचनाओं को केवल इलेक्ट्रॉन माइक्रॉस्कोप के द्वारा ही देखा जा सकता है। इनकी रचना 50% प्रोटीन तथा 50% आर॰ एन॰ ए॰ द्वारा हुई होती है। ये विशेषकर अंतर्प्रद्रव्य जालिका के ऊपर पाए जाते हैं। इनमें प्रोटीनों का संश्लेषण होता है।

सेंट्रोसोम (centrosomes)– ये केंद्रक के समीप पाए जाते हैं। इनके एक विशेष भाग को सेंट्रोस्फीयर (centrosphere) कहते हैं, जिसके भीतर सेंट्रिओलों (centrioles) का एक जोड़ा पाया जाता है। कोशिका विभाजन के समय ये विभाजक कोशिका के ध्रुव (pole) का निर्धारण और कुछ कोशिकाओं में कशाभिका (flagella) जैसी संरचनाओं को उत्पन्न करते हैं।

लवक (plastids)

लवक अधिकतर पौधों में ही पाए जाते हैं। ये एक प्रकार के रंजक कण (pigment granules) हैं, जो जीवद्रव्य (protoplasm) में यत्र तत्र बिखरे रहते हैं। क्लोरोफिल (chlorophyll) धारक वर्ण के लवक को हरित्‌ लवक (chloroplas) कहा जाता है। इसी के कारण वृक्षों में हरापन दिखलाई देता है। क्लोरोफिल के ही कारण पेड़ पौधे प्रकाश संश्लेषण (photosynthesis) करते हैं। कुछ वैज्ञानिकों के मतानुसार लवक कोशिकाद्रव्यीय वंशानुगति (cytoplasmic inheritance) के रूप में कोशिका विभाजन के समय संतति कोशिकाओं में सीधे सीधे स्थानांतरित हो जाते हैं।

science guruji

Use of Vermi compost in crops

vermi compost

Vitamins and Minerals

Vitamins and Minerals •

How do you get your vitamins?

Vitamins and Minerals

Vitamins

Minerals

BIOTECHNOLOGICAL APPLICATIONS IN MEDICINE

BIOTECHNOLOGICAL APPLICATIONS IN MEDICINE

Genetically Engineered Insulin

Gene Therapy

Molecular Diagnosis

ELISA is based on the principle of antigen-antibody interaction. Infection by pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesised against the pathogen.

Structure of Polynucleotide Chain

THE DNA

Structure of Polynucleotide Chain

आपका शरीर ठंड के लिए कैसे प्रतिक्रिया करता है?

आपका शरीर ठंड के लिए कैसे प्रतिक्रिया करता है?

होमियोस्टैसिस और प्रतिक्रिया विनियमन

होमोस्टैसिस को बनाए रखना

सकारात्मक प्रतिक्रिया

सारांश •

मानव जीवविज्ञान

मानव जीवविज्ञान की परिभाषा

मानव जीवविज्ञान का इतिहास

Myst ery of space

Myst ery of space

Usually when we boil water, many bubbles are formed in it. But this does not happen in space. A large bubble is formed when the water is heated there. The reason is also gravity.

Studies on germs for 30 years have shown that germs spread more rapidly in space than on Earth and are also more dangerous.

Drinking soda in space can be dangerous. There is difficulty in digesting soda here. It is alsobecause of gravity. This is the reason why experiments are being done on space beer in Australia

BIOTECHNOLOGICAL APPLICATIONS IN AGRICULTURE

BIOTECHNOLOGICAL APPLICATIONS IN AGRICULTURE

Let us take a look at the three options that can be thought for increasing food production

(i) agro-chemical based agriculture;

(ii) organic agriculture; and

(iii) genetically engineered crop-based agriculture.

Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO). GM plants have been useful in many ways. Genetic modification has:

(i) made crops more tolerant to abiotic stresses (cold, drought, salt, heat).

(ii) reduced reliance on chemical pesticides (pest-resistant crops).

(iii) helped to reduce post harvest losses.

(iv) increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil).

(v) enhanced nutritional value of food, e.g., golden rice, i.e., Vitamin ‘A’ enriched rice.

In addition to these uses, GM has been used to create tailor-made plants to supply alternative resources to industries, in the form of starches, fuels and pharmaceuticals.

Bt Cotton:

(Figure-1) - Cotton boll: (a) destroyed by bollworms; (b) a fully mature cotton boll

(Figure-2)Host plant-generated dsRNA triggers protection against nematode infestation:(a) Roots of a typical control plants; (b) transgenic plant roots 5 days after deliberateinfection of nematode but protected through novel mechanism

BIODIVERSITY

POPULATION STABILISATION AND BIRTH CONTROL IN INDIA

TISSUE CULTURE

Animal Breeding

Animal husbandry

fact of space

Recombinant DNA technology

Recombinant DNA technology

DNA cloning

Cell-based DNA cloning

Construction of recombinant DNA molecules

Transformation

Seltive propagation of cell clones

Isolation of recombinant DNA clones

Cell-free DNA cloning

Enzymes for DNA manipulation

Nucleases

Mung bean nuclease

S1 nuclease

RNase

life on Mars

Signs of water

ब्लैक होल क्या है?

Chromosomal basis of inheritance

Genetics

जन्तु ऊतक (animal tissue)

उपकला (Epithelial Tissue)

संयोजी ऊतक (Connective tissue)

पेशी ऊतक (Muscular Tissue)

तंत्रिका ऊतक (Nervous Tissue)

स्केलेरस ऊतक

cell organ {कोशिकांग}

Studies on germs for 30 years have shown that germs spread more rapidly in space than on Earth
and are also more dangerous.

Drinking soda in space can be dangerous. There is difficulty in digesting soda here. It is also
because of gravity. This is the reason why experiments are being done on space beer in Australia