surii knowledge

What is Data Base and classification of Data Base ?

Environment / what is Environment ?

2020-09-02T15:50:00.003+05:30

Environment has different meaning for different people. Most definitions includes the physical, chemical and biological components that influence the life of an organism. Among biological component, the human (homo sapiens) occupies a central position as one of the organisms. A recent development (post-1972 stockholm conference ) has been the emphasis on impact of man itself on its own environment i.e., The various anthropogenic activities affecting the environment at global level. For instance, several socio-economic, cultural and political factor also influence the basic physical, chemical and biological components (and their interactions) of the environment. As a result persons led by different discipline have approach the environment in different ways, which should be evident from the various definition of the environment proposed by them. Such definition of the environment on the web are as follows:

· The sum of all the external conditions that are affecting the life, development and survival of an organism.

· All the external factors, conditions and influences that affect an organism or a biological community.

· Surrounding in which an organization operators, includes air, water, land natural resources, flora, fauna, humans and their interaction.

· The interaction with climate, soil, topography, and other plants and animals in any given area. An organism’s environment influences its form, behaviour and survival.

· An complex set of physical, geographical, biological, social, cultural and political condition that surround an individual or organism and that ultimately determines its form and nature of its survival.

· The combination of all physical and other factor and condition that influence the development and survival of an organism or group of organisms.

· The component of the earth that include: (1) air, land and water; (2) The layer of the atmosphere; (3) organic and inorganic matter and living organisms; (4) the interacting system that include components referred to in (1) to (3); and the socio-economic, environmental health, culture and other items referred to in the definition of the environmental effect.

· The Non-genetic conditions and circumstances that affect a person’s conduct and health.

· The conditions, influences, or forces which affects the desirability and value of property, as well as the effect on people’s lives.

· Physical and interpersonal surroundings that can affect mood and behaviours in people with dementia.

· The social environment of an individual is culture that he or she was educated and / or lives in, and the people and institutions with whom the person interacts.

Fig:- Nature

The term environment etymologically means surrounding. Thus, environment is the complex of many things (light, temperature, soil, water, etc.) which surround an organism. Any external force, substances or condition, which surrounds and affects the life of an organism in any way, becomes a factor of its environment. These factor have been variously called environmental factors, ecological factors or simply factors and may be living (biotic). The sum of all these living and Non-living factors makes the environment of an organism. The place, where an organisms lives – habitat, indeed presents a particular set of environmental conditions – the environmental complex.

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Overlapping gene/ Genes within Genes / overlapping

2020-08-30T18:20:00.003+05:30

In 1940, Beadle and Tatum proposed one-gene –one protein hypothesis which explains that one gene encodes for one protein. However, If one gene consists of 1,500 base pair, a protein of 500 amino acids in length would be synthesized. In addition, if the same sequence read in two different ways, two different amino acid would be synthesized by the same sequence of base pair. It means, the same DNA sequence can be synthesized more than one protein at different time. It was realised for the first time when the total number of protein synthesized by ÆX174 exceeded from the coding potential of the phage genome. A similar phenomenon is found in the tumour virus SV40 where the total molecular weight of protein (i.e. VP1, VP2, and VP3) synthesized by SV40 gene is much more than the size of the DNA molecule (5,200 base pair i.e. 1,733 codons). Form this observation concept of overlapping gene has emerged.

Fig :- DNA helix

For the first time B.G. Barrell and co-workers in 1970 gave the evidence for the possibility of the above fact based on the overlapping genes found in bacteriophage ÆX174. This virus contains an icosahedral capsid with the knob of each vertex enclosing the single stranded circular DNA (fig). F.Sanger and co-workers in1977 mapped the whole nucleoside sequence of phage ÆX174, and phage G4 DNA. The sequence of genes D, E and J, and B, to overlapping in the whole sequence of ÆX174.

The ÆX174 strand is made up of 5,386 nucleotide of known base sequences. If a single reading frame was used, about 1,795 amino acid would be encoded in the sequence and with and average protein size of about 400 amino acids, only 3-5 proteins could be made. In contrast, ÆX174 makes 11 proteins containing of total more than 2,300 amino acids. The sequence of gene A is now known to contain all of gene B. Gene B is translated during a different reading frame from gene A. similarly gene E is encoded within gene D. Another translational control mechanism expand the use of gene A. The 37 k Dalton gene A* protein is found by reinitiating translation at an internal AUG codon within gene A message. The two translational proteins are synthesized by the same translational phase but the function of two proteins differ. Protein K initiated near the end of gene A, includes the base sequence of gene B, and terminates in gene C. For example, a reading frame of …… G,AAG,TTA,ACA…… nucleotides encodes the amino acid lysine, leucine and threonine. However, after reading the frame one nucleotide earlier, the codes become... GAA,GTT,AAC,A…. that encode glutamine, valine and asparagines, respectively.

It is obvious that by shifting the reading frame i.e. overlapping the code, the same gene can codes two different proteins. Similarly, in the nucleotide sequence …. TAATG…., TAA act as termination code of gene D, and ATG acts as initiation code of gene J. Here the nucleotide ‘A’ between A and T overlaps between the two codes. Therefore, the amino acid sequence of A* similar to the segment of protein A. In addition, overlapping genes have also been detected in animal virus SV40, and tryptophan mRNA of E.Coli.

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Infertility in Human/ Infertility in men / Infertility

2020-08-25T15:27:00.002+05:30

There are large number of reasons for developing infertility in humans. By using IVF many more infertility have been treated.

Who benefits IVF: It is not likely that any patient of any age or any group of society goes for treatment of IVF. There are some prerequisite conditions applicable for male and female partner. The male should not azoospermic ( very low no. of motile sperm); however if he is azoospermic and desired for a baby, he can procure sperm either from sperm bank or elsewhere. Beside, the female partner should also be healthy and fit for IVF because it is she who is to bear the pregnancy. Therefore, the female must such that; (1) any surgical procedure should not create any trouble for her, (2) her ovary should be accessible for oocytes, (3) her uterus should accept and bears pregnancy for the required period of ninth months, and (4) her cervical canal should be easily negotiable for embryo transfer.

Fig:- Baby in mother's uterus

(a) Male sterility: In fertile human the total count of sperms should be 15-20 million per ml. when the number of sperm of decreases, the person is called oligospermic and the condition as oligospermia. Similarly, when there is very low number of motile sperm, the patient is called azoospermic and the phenomenon as azoospermia. Generally, in azoospermic humans the number of non-motile sperm is high. In addition, for IVF, the presence of motile sperm should be around 10-20,000 per ml.

(b) Female sterility: There are several reasons and types of female infertility; few of them are;

(1) non-functional (inaccessible or absent) ovaries (some time ovaries of female are non-functional or inaccessible, therefore, healthy oocytes will not produced. In such cases oocytes can be procured from donor for IVF).

(2) Non-functional (or absent) uterus (in this condition the oocytes are obtained from female and subjected to IVF, and embryo transferred to surrogate mother for pregnancy and futher development),

(3) Idiopathic infertility -no definite cause is known for idiopathic infertility. Possible it may be due to abnormal fertilization or failure in fertilization. Therefore, IVF followed by embryo transfer will cure this infertility, and

(4) tubal infertility (fallopian tubes receives follicles of ovaries for fertilization. Any deformity in fallopian tube result in tubal infertility. IVF followed by embryo transfer in uterus has replaced the function of fallopian tubes. Therefore, the patient will not be subjected to surgical treatment).

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Blotting techneques/ DNA replication

2020-08-19T17:40:00.005+05:30

DNA,RNA and protein are separated by blotting techniques. These are described below:

Fig: DNA

1. Southern blotting techniques

A method developed by molecular biologist E.M. Southern (1975) for analysing the foreign gene in a DNA restriction fragment is called southern blotting technique. Southern blots can be easily provide a physical map of restriction sites within a gene located normally on chromosome, and reveal the number of copy of gene in the genome, and the degree of similarity of the gene when compared with the other complimentary genes.

Fig: procedure of sodium blotting technique.

DNA isolated from a given sample is digested with one or many restriction enzymes (Fig.1). consequently, DNA fragments of unequal lengths are produced. This preparation is passed through agarose gel electrophoresis which result in separation of DNA fragment based on their size. DNA restriction fragment present in gel are denatured by alkali treatment. Gel is then put on the top of the buffer saturated filter paper. The dry filter paper draws the buffer through the gel. Buffer contain single stranded DNA. Nitrocellulose filter binds DNA fragments strongly then come in contact of it. After baking in at 80°C, DNA fragments are permanently fixed to the nitrocellulose filter. Then the filter is placed in the solution containing radio-labelled RNA or denatured DNA probe of known sequences. These are complimentary in sequence to blot-transferred DNA.

The radiolabelled nucleic acid probe hybridized the complimentary DNA on nitrocellulose filter. The filter is thoroughly washed to remove the probe. The hybridized region are detected autoradiographically by placing the nitrocellulose filter in contact with photographic film. The image shows the hybridized DNA molecule. This, the sequence of DNA are recognized following the sequence of probe.

2. Northern blotting techniques

Southern blotting technique could not applied directly to the blot transfer of mRNA separated by gel electrophoresis, because RNA was found not to bind with nitrocellulose filter. J.C.Alwine and co-workers in 1979 devised a technique in which RNA was blot transferred from the gel into chemically reactive paper. In aminobenzyloxymethyl cellulose paper, prepared from whatman filter paper No. 540 after a series of uncomplicated reactions, is diazotised and rendered into the reactive paper and, therefore, available for hybridization with radiolabelled DNA probe. The hybridized bands are found out by autoradiography. Thus, Alwine’s method extends that of southern’s method and for this reason it has been given the jargone term ‘northern blotting’. Like southern, there is nothing northern or western.

These blot transfer are reusable because of the firm covalent bonding of RNA to the reactive paper. The chemically paper is equally effective in binding the denatured DNA as well. Small fragment of DNA can more effectively be transferred to the diazotised paper derivative than to nitrocellulose. These techniques were more being advanced and more recently have been demonstrated that mRNA bands can also be blotted directly on nitrocellulose paper under appropriate condition. In this method preparation of reactive paper is not required. The mRNA is isolated from the transformed cell and electrophoresed under such conditions that don not permit the development of secondary structures. The mRNA separated on the gel are transferred on nitrocellulose filter which are than hybridized to single stranded probe (RNA or DNA ). Thereafter, hybrid are treated with SI nuclease and RNAase which digest the single stranded RNA/DNA probe. It does not affect the double stranded nucleic acid formed due to hybridization of RNA by the complimentary sequences of nucleic acid probe. Structure of mRNA is revealed to the extent to which mRNA protect the nucleic acid probe.

3. Western blotting techniques (protein blotting or electroblotting technique)

In 1979, H.Towbin and co-workers developed the western blotting technique to findout the newly encoded protein by a transformed cell. Its working principle lies on antigen-antibody reaction; hence, it is an immuno detection technique. In this method radiolabelled nucleic acid probe are not used. This technique follow the following steps:

(1) Extraction of protein from transformed cells.

(2) Separation of protein by using SDS-PAGE (sodium dodicyl sulphate polyacrylamide gel electrophoresis) where SDS acts as solvent for electrophoresis.

(3) Transfer of electrophoresed cell in a buffer at low temperature (40°C) for half an hour.

(4) Blotting of protein onto nitrocellulose filter paper.

(5) Soaking of nitrocellulose filter, Whatman filter and coarse filter in transfer buffer.

(6) Placing of whatman filter paper on a cathode plate followed by stalk of coarse filter, whatman filter, electrophoresed gel, nitrocellulose filter, whatman filter paper, coarse filter stack, whatman filter and anode plate (fig.2).

Fig: Western blotting by using radiolabelled antibodies and detecting the bands through autoradiography.

(7) Putting the complete set up in a transfer tank containing sufficient transfer buffer.

(8) Application of an electric field (30 V overnight for 5 hours) to cause the migration of protein from the gel to nitrocellulose filter and binding on its surface. (The nitrocellulose filter has exact image of pattern of proteins as present in the gel. This type of blotting is called western blotting.)

(9) Hybridization of protein by using radiolabelled antibodies (I¹²³- antibodies) of known structure, isolated from the rabbit.

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Gene library or DNA library

2020-08-18T17:44:00.003+05:30

A gene library is the collection of different DNA sequence from an organism where each sequence has been cloned into a vector for ease of purification, storage and analysis. There are two types of libraries on the bases of source of DNA used: (1) genomic library (where genomic DNA is used), and (2) cDNA library (where cDNA or complimentary DNA is produced using mRNA). A gene library should contains a certain number of recombinants with a high probability of containing any particular sequence. This value can be calculated when you know the genome size and average size of inserted into the vector.

Figure:- science laboratory

The probability of getting a given gene sequence in a gene library, the number (N) of recombinants ( bacterial colonies or viral plaques) can be calculated by using following formula:

(IN (1-P)/(IN (1-f) = N

Where, P = the desired probability and f = the fraction of one genome in one insert. For a probability of 0.99 with insert size 2× 10⁴bp, the value of genome for E.coli (4.6 × 10⁶bp) will be:

N^E.Coli= 〖(In (1-0.99))/(In ⌊(1-(2×(20^4)/4.6×10^6)⌋ )〗^ = 1.1 ×10^3

1. 1. Genomic library

It is a collection of clones that represent the complete genome of an organism. All fragments of DNA are inserted into vector for further propagation into suitable host represent the entire genome of an organism. For construction of genomic library the entire genomicDNA is isolated from host cell/tissue, purified and broken randomly into fragments of correct size for cloning into a suitable vector. We have two basic ways of fragmenting genomic DNA randomly: physical shearing (e.g. pipetting, mixing or sonication) and partial restriction enzyme digestion (by using limited amount of restriction enzyme the DNA is not digestion at every recognition sequence). Using these method genomic DNA is broken randomly into smaller fragments.

Fig. Construction of genomic library.

Fig. shows a total of 6 random DNA fragment obtained after physical sharing. The vector isolated from bacterium is also digested with the restriction enzyme which digest genomic DNA. The fragment of genomic DNA is inserted into the vector. Each vector consists of different fragments of DNA. The recombinant DNA molecule are transferred into the bacterial cell or bacterial cell or bacteriophage particles are assembled.

The genomic library for organisms with smaller genomic size (e.g. E.Coli) can be constructed in plasmid vector. Only 5,000 clones (of the average size of 5,000 bp) result in 99% chance of cloning the entire genome of 4.6 × 10⁶bp. In addition, library from organisms with larger genomes are constructed using phage l, cosmid, BAC or YAC vector.

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Chemical nature of DNA /dna / What is DNA?

2020-08-14T17:59:00.003+05:30

DNA is found in all plants , animals, prokaryotes and some viruses. In eukaryotes it is present inside the nucleus, chloroplast and mitochondria, whereas in prokaryotes it is dispersed in cytoplasm. In plant, animal and some viruses DNA is double stranded (ds) DNA molecules except some viruses such as fX174. IN TMV, influenza virus, polionylitis virus and bacteriophage the genetic material is single stranded (ss) RNA molecule (Table.1). The entire genetic message which control the chemistry of every cell of the body acting in a specific way is actually written in the language of four nitrogen bases of DNA i.e. purines and pyrimidines. The defined sequence of four bases constitutes a ‘gene’ which may be few or several hundred base pair long. Genes are the structure of the blue prints called protein which control the infinite variety of life.

Table.1 Nature of genetic material

DNA / RNA	Examples
Double stranded DNA (dsDNA)	Higher plants, animals, bacteria, animal viruse (polyoma virus, small pox ,herpes virus), Bacteriophage( T-even)
Single stranded DNA (ssDNA)	Bacteriophage (f X174 and other bacteriophage), animal viruses (parvovirus)
Double stranded RNA (dsRNA)	Retrovirus, reovirus, Hepatitis-B virus, anima virus, plant virus (tobacco mosaic virus)
Single stranded RNA (ssRNA)	Animal viruse (influenza virus, poliomylities virus), Bacteriophages (F_2’ ~ R₁₇)

Fig. DNA

1. 1. Chemical composition

Purified DNA isolated from plants, animals, bacteria and viruses has shown a complex form of polymeric compounds containing four monomers known as deoxyribonucleotide monomers or deoxyribotides (fig.1). Each deoxyribonucleotide consists of pentose sugar (deoxyribose), a phosphate group and a nitrogenous base (either purine or pyrimidine). Purines bases (adenine and guanine) are hetrocyclic and two ringed bases and the pyrimidines (thymine and cytosine) are one ringed bases. The following compounds are of deoxyribonucletide have been described:

Fig;- A typical nucleotide showing its components: Base, sugar and phosphate.

(a) A five carbon ring.

Deoxyribose is a pentose sugar consists of five carbon atom. Four carbon atoms (1’,2’,3’,4’) of this sugar combined with one oxygen atom and form a ring. The fifth atom (5’) forms –CH₂ group which is present outside the ring. Three –OH group are attached at the position 1’ ,3’ and 5’ and the hydrogen atom combined at position 1’, 2’, 3’ and 4’ of carbon atoms (Fig.1). In ribonucleotides, the pentose sugar is ribose which is similar to deoxyribose except that there is an –OH group instead of –H at 2’ carbon atom. The abence of –OH group in DNA make it chemically more stable than RNA.

(B) Nitrogenous bases.

There are two nitrogenous bases purines and pyrimidines. The purines are double ringed compounds that consists of 5-membered imidazole ring with nitrogen at 1’,3’, 7’ and 9’ position. The pyrimidines are one ring compounds, the nitrogen being at the position 1’ and 3’ in 6-membered benzene ring. A single base is connected to 1’-carbon atom of pentose sugar by N-glycosidic bond. Purines are of two types, adenine (A) and guanine (G), and pyrimidines are also of two types , thymine (T) and cytosine (C). Uracile (U) is the third pyrimidine (fig.2). A, G and C are common found in both DNA and RNA. U is found only in RNA.

(b) A phosphate group.

In DNA a phosphate group (PO₄^3- ) is attached to 3’-carbon of deoxyribose sugar and 5’-carbon of another sugar. Therefore, each and every strand contains 3’ end and 5’ end arranged in an alternate manner. Strong negative charges of nucleic acid are due to the presence of phosphate group. A nucleotide is a nucleoside phosphate which contains its bond to 3’ and 5’ carbon atom of pentose sugar that is called phosphodiester.

(Fig.2) Nitrogen bases of nucleic acids.

2. 2. Nucletides and Nucleosides

The nitrogen bases combined with pentose sugar are called nucleosides. A nucleoside linked with phosphate forms a nucleotide (Fig.1)

Nucleoside = pentose sugar + Nitrogenous bases

Nucleotide = nucleoside + phosphate

On the bases of different nitrogenous bases the deoxynucleotide are of following types:

(a) Adenin (A) = deoxyadenosine-3’/5’-monophosphate (3’/5’ –d AMP)

(b) Guanin (G) = deoxyguanosine-5’-monophosphate (5’ –d GMP)

(c) Thyamine (T) = deoxythymidine-5’-monophosphate (5’ –d TMP)

(d) Cytocine (C) = deoxycytidine -5’-monophosphate (5’ –d CMP)

In addition to the presence of nucleosides in DNA helix, these are also present in nucleoplasm and cytoplasm in the form of deoxyribonucleotide phosphate e.g. deoxyadenosine triphosphate (dATP), deoxyguanosine triphosphate (dGTP), deoxycytidine triphosphate (dCTP) , deoxythmidine triphosphate (dTTP). The advantage of this four deoxyriboncletide in triphoshate form is that the DNA polymerase acts only on triphosphate of nucleotides during DNA replication.

Similarly, the ribonucleotides contains ribose sugar, nitrogenous bases and phosphate. Except sugar, the other components are similar. However, uracil (U) is found in RNA instead of thymine. Generally, RNA molecule is single stranded beside some exceptions.

3. 3. Polynucleotide

The nucleotides undergo the process of polymerization to form a long chain of polynucleotide. The polynucleotides are designated by prefixing ‘poly’ to each repeating unit such as poly A (polyadenylic acid), poly T (polythymidilic acid), poly C (polycytidilic acid), poly G (polyguanidylic acid) and poly U (polyuridylic acid). The polynucleotides that consists of the same repeating unit are called homopolynucleotides such as poly A, poly T, poly C, poly G and poly U.

4. 4. Chargaff-equivalent rule

By 1948, a chemist Erwin chargaff started using paper chromatography to analyse the base composition of DNA from a number of studies. In 1950, chargaff discovered that in DNA of different type of organisms the total amount of purines is equal to the total amount of pyrimidines, i.e. the total no. of A is equal to the total no. of T (A-T), and the total no. of G is equal to the total no. of C (G-C). It means that A/T = G/C, i.e. A+T/G+C = 1. In DNA molecules isolated from several organisms regularity exists in the base composition.

The DNA molecule of each species comprises of base composition which is not influenced by either environmental conditions or growth stage or age. The molar ratio i.e. [A] +[T]/[G]+[C] represents the characteristic composition of DNA of each species. However, in higher plants and animals A-T composition was found genetically high and G-C content low, whereas the DNA molicules isolated from lower plants and animals, and bacteria and viruse was generally rich in G-C and poor in A-T contents (Table 2). The two closely related species will have very similar molar % G+C values and vice versa. Thus, the use of base composition has much significance in estabilashing relationship between two species and in taxonomy and phylogeny of species.

Table 2. Relative amount of nitrogenouse bases in DNA isolated from different organisms.

Source	Adenine	Guanine	Thymine	Cytosine	A+T/G+C
Human sperm	30.9	19.1	31.6	18.4	1.62
Human thymus	30.9	19.9	29.4	19.8	1.52
Sea urchin sperm	32.8	17.7	32.1	18.4	1.85
Wheat germ	26.5	23.5	27.0	23.0	1.19
Yeast	31.3	18.7	32.9	17.1	1.79
Escherichia coli	26.0	24.9	23.9	25.2	1.00
Diplococcus pneumonia	29.8	20.5	31.6	18.0	1.59
Bacteriophage T₂	32.5	18.2	32.6	16.7	1.86
-	-	-	-	-	-

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COSMIDS/ what is cosmid

2020-08-12T18:09:00.003+05:30

Based on the properties of DNA and col El plasmid DNA, a group of Japanese workers showed that the presence of a small segment of phage ï¬ DNA containing cohesive end on the plasmid molecule is sufficient prerequisite for in vitro packaging of this DNA into infectious particles. The cosmid can be defined as a hybrid vector derived from plasmids which contain cos site of phage l (cosmid = cos site +plasmid). For the first time it was developed by H.A Collins and M.Hohn in 1978.

Figure:- DNA

Cosmid lack gene encoding viral protein; therefore, neither viral particle are formed with the host cell nor cell lysis occurs. Special feature of cosmid similar to plasmid are the presence of: (a)origin of replication, (b) a marker gene coding for antibiotic resistance, (c) a special cleavage site for the insertion of foreign DNA, and (d) the small size.

Extra phage DNA of cos site about 12 bases is present. It help the entire genome in circularization and ligation. The cosmid has the length of about 5 kb, the upper size limit of the foreign DNA fragment that may be inserted in cosmid and packed into phage particles, therefore, approximately 45 kb, much larger than it might be possible to clone in phage lor phage vector (Dahl et al., 1981). According to the size of cos site and upper size limit in the head of phage, the recombinant DNA molecule can be packed into bacteriophage particles in in vitro packaging system consists of packaging enzyme, head and tail proteins. Procedure of DNA cloning by using cosmid vector is shown in fig.. upon transfection of E. coli by bacteriophage, the recombinant DNA cyclises through cos site and then replicate as a plasmid and expresses the drug resistance marker. Recently, based on cosmid vector have been determined from E. coli, yeast, and mammalian cells, and gene bank has been constructed.

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units of gene / How it was discovered

2020-08-10T16:45:00.005+05:30

Gene: A gene can be defined as a polynucleotide chain that consists of segments each controlling the particular trait.

Fig:- science lab

Units of gene: there are three units of gene

(1 (1)Cistron (unit of function)

One-gene-one enzyme hypothesis of Beadle and Tatum. A single mRNA is transcribed by a single gene. Therefore, one-gene-one mRNA hypothesis was put forth. Exceptionally, a single mRNA is also transcribed by more than one gene and it is said to be polycistronic. Therefore, the concept of one gene one protein hypothesis. The protein are the polypeptide chain of amino acid translated by mRNA. Therefore, it has been correctly used as one-gene-one polypeptide hypothesis.

Moreover, genes are present within the chromosomes and their cis-trans effect governs the chromosome function. Therefore, S.Benzer term the functional gene as cistrone (shown in figure A). Crossing over within the functional gene or cistrone are possible. The cis-trans arrangement of the alleles may be written as below:

++/a b a+/+b / = it shows divide sign

Cis(wild) trans(mutant)

fig. The genes as unit of functions i.e. custron (A), recombination i.e. recon (b) and mutation i.e. muton (c)

(2) Recon (unit of recombination)

Earlier, it was thought that crossing over occurs between two genes. In 1962, S.Benzer demonstrated that crossing over or recombination occurs within a functional gene or cistron. In a cistron recombinational unit may be more than one. Thus, the smallest unit capable of undergoing recombination is known as recon (fig.B).

S.Benzer (1955) found that the culture of T4 bacteriophage formed plaques on agar plates of Eschcherchia coli. Normal T4 formed small plaques of smooth edges, where the mutant T4 phage formed the large plaques of rough edges. The DNA molecule of T4 phage consists of several genes one of which is called r2 region. Formation of rough edged plaques was govern by two adjacent genes ( cistrons r2A and r2B ) in mutant bacteriophage. Both the region function independently and consists of 2,500 and 1,500 nucleotide, respectively. In r2A gene over 500 mutant sites are present where crossing over may occur. Though crossing over exchange of two segments of DNA occurs. If crossing over occur within the gene, by matting two r2 mutant of T4 phage a normal wild type will be produced. Thus, the work of benzer lends supports the crossing over within the gene occurs, which explains that the recombinational unit (recon) is much less smaller than the functional unit i.e. cistron.

(3) Muton (unit of mutation)

S.Benzer (1962) coined the term mutan to donate the smallest unit of chromosome that undergoes mutational changes. Hence, mutan may be defined as ‘the smallest unit of DNA which may be changed in the nucleotide. Thus, changes at the nucleotide level are possible (fig.C). The smallest unit of mutan is nucleotide. Therefore, cistron is the largest unit in size followed by recon and mutan. This can be explained that the gene consists of several cistron contains many recon, and a recon a number of mutans. However, if the size of a recon is equal to mutan, there would be no possibility in recon for consisting of several mutans

What is Data Base and classification of Data Base ?

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What is database ? / classification of database

2020-08-09T16:28:00.004+05:30

A database is a repository of sequence (DNA or amino acid) which provides a centralised and homogeneous view of its content. The repository is created and modified through a database management system (DBMS). Every data item in the database is structured according to scheme, defined as a set of pre-specified rules through the data definition language. The contents of database can be access through a graphical user interfase (GUI) that allows browsing through the contents of repository very much similar as one may browse through the books in library.

Most database also allow querying of its content through a specialized query language. The data definition language and the query language from the data modal.

Classification of database: The database are broadly classified into two broad categories:

(1) sequence databases (that involves the sequence of both proteins and nucleic acids),

(2) structural database (that involves only protein database).

In addition, it is also classified into three categories (a) primary database, (b) secondary database, (3) composite database.

Primary database contain information of the sequence or structure alone of either protein or nucleic acid e.g. PIR or protein sequence, gene bank and DDBJ for genome sequences. Primary database tools are effective for identifying the sequence similarities, but analytics of output is sometimes difficult and cannot always answer some of the more sophisticated questions of sequence analysis. In 1998, gene bank obtained a millions of sequence from more than 18,000 organisms.

Secondary database contains derived information from primary database, for example, information on conserved sequence, signature sequence and active sites residues for protein families by using SCOP, eMOTUIF, etc. It is more useful than primary databases. Orthology provides an important layer of information when considering phylogenetic relationship between the genes. Depending on the type of analysis method used, relationship may be elucidated into considerable detail including superfamily, family, sub-family and species-specific sequence levels.

Composite database is obviating the need to search multiple resources. The scope is structural classification of protein in which the proteins are classified into hierarchial levels such as classes, folds, super-families.

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What is Bioinformatics?

2020-08-08T18:13:00.004+05:30

‘’Bioinformatics is the application of information science (mathematics, statics and computer science) to increase our understanding of biology’’.

Translation of billions of characters in DNA sequences that makes the genome into biologically meaningful information has given birth to a new field of science called ‘Bioinformatics’. The term bioinformatics has been derived by combining biology and informatics. The key of biotechnology is locked in the genomes of organisms. The informatics holds the key to unlock these data for the next generation of innovations.

In the broadest sense the biotechnology can be considered as information technology applied to management and analysis of biological data. But in view of recent rapid accumulation of available protein structure, this term is also used to embrace the manipulation and analysis of three dimensional structure of data. Thus bioinformatics is a multidisciplinary science which to use the benefits of computer technologies in understanding the biology of life. Now, as a subject bioinformatics consists of three core areas;

(1) molecular biology database,

(2) sequence comparison and sequence analysis,

(3) the emerging technology microarrays.

In brief,'' bioinformatics is the management and analysis of biological information stored in database''.

What is Data Base and classification of Data Base ?

How infertility in Haman occur ( male and female ) ?

Types of gene therapy

2020-08-05T18:16:00.015+05:30

All the gene therapy are done on human and can be done in human and classified into following four types.

(1)Somatic gene therapy:- The genetic defects are corrected in somatic cells of the body. It was initially formulated for the treatment of monogenetic defects, but now holds promises for a wide range of disorders such as cancer, neurological disorders, heart diseases and infectious diseases(Table 1).sufficient expertise in performing successful gene transfer in somatic cells is required before carrying out gene manipulation in human.

Fig:- DNA

Table 1.Genetic disorder and acquired diseases amenable to gene therapy.

Diseases		Therapeutic agent	Strategy	Vector	Target cell/tissue
Genetic disorder
Cystic fibrosis		CFTR	In vivo	Adenovirus	Nasal epithelium
Familial hypercholesterolaemia		LDL	In vivo	Cationic lipids	Nasal epithelium
SCID		ADA	Ex vivo	Retrovirus	T cell
Heamophilia		Factor 8/9	In vivo	Retrovirus	Hepatocytes,skin,muscles
DMD		Dysterophine	In vivo	Retrovirus	Skeletal muscles

Acquired disorder
Alzheimer’s disease		NGF	Ex vivo	Retrovirus	Tumour cells
AIDS		HIV agent	Ex vivo	Retrovirus	T cells
AIDS		RevM10	Ex vivo	Retrovirus	Hepatocyte
Cancer		Cytokine	Ex vivo	Retrovirus	Hepatopoitic stem cells
		Interleukins,	Ex vivo	Retrovirus	Tumour cells
		HSV-TK	Ex vivo	Retrovirus	Tumour cells
		HLA	In vivo	Cationic lipid	‘’
		Tumour suppressor gene	In vivo	Cationic lipid	‘’
Cardiovascular disease	tPA		In vivo	Adenovirus	Tumour cells
Parkinson’s disease	TH		Ex vivo	Retrovirus	Fibroblast

CFTR, cystic fibrosis transmembrane regulator, SCID, sever combined immunodeficiency syndrome ,DMD , duchennne muscular systrophy, ADA, adenosine deaminase; HSV-TK, herpes simplex virus thymidine virus, NGF, nerve growth factor TH, tyrosine hydroxylase, tPA, tissue plasmogen activator.

(2) Germ line gene therapy. The functional gene are introduce into the germ cell for correction of genetic defects in the offspring. This therapy is being carried out in laboratory and farm animals. However, it has not been attempted in humans due to technical and ethical problems. One of this type is embryo therapy where embryos are diagnosed for genetic defects. If any such disease is present the patient are adevised for embryo therapy or abortion. In young embryo a functional gene is transferred through microinjection technique.

(3) enhancement genetic engineering. This type of gene transfer is done for the improvement of a specific trait in animals; for example introduction of growth hormone gene in to increase height. It is being carried out in laboratory and farm animals.

(4) Eugenic genetic engineering. Novel gene can be introduced in humans to alter or improve complex trait such as intelligence and personality. This type of therapy is not being attempted in humans because it is far away from technical capabilities, and ethical problems.

In 1990, for the first time , Michal Blease and w.french Andresco of national institute of health,Bethesda , U.S.A attempted gene therapy on a human patient. A four year old girl was suffering from ‘severe combined immunodeficiency’(SCID). This disease is caused by a faulty gene which express the enzymes adenosine deaminase (ADA). Deficiency of ADA result in the production of chemical which selectively distroyes the T- and B-cells of immune system. Finally, the patient die. The scientist finally introduce a healthy ADA gene in the body of girl who protect her immune system from damage. This successful trail has given the signal for the draw of new era in the field of medical science.

What is Data Base and classification of Data Base ?

How infertility in Haman occur ( male and female ) ?

What is gene therapy?

2020-08-03T13:57:00.007+05:30

Gene therapy

"The ultimate goal of gene therapy is that the gene replacement therapy''.

Gene are the last word molecular switches that control various cellular process.The abnormal gene can manifest within the sort of specific gene disorders.until the last decade ,delivering gene into human to correct diseases has been accepted as scientifically viable and recognised as independent discipline and christened ''gene therapy''.

The ultimate source of gene therapy if the gene replacement therapy.Gene replacement therapy permits physiological regulation of the transgenes and elimination of the likelihood insertional inactivation of other of other cellular genes which occur at the time of random integration of the foreign gene.At present the present strategy for gene therapy largely centers around gene augmentation therapy,where the foreign gene replaces the defective or missing gene.

Overall, there are two strategy for gene transfer;(1) the in vivo approach which involves introduction of gene directly into the target organs of a private (it is completed in patients therefore,also called patient therapy), (2) ex vivo approach where cells are isolated for gene transfer in vitro followed by transplantation of genetically modified cell back to patients.

What is Data Base and classification of Data Base ?