Biology Answer the following questions in detail.

1. A small amount of beta-galactoside permease enzyme is present in cell even when Lac operon is switched off and it allows a few molecules of lactose to enter into the cell.
2. Lactose binds to repressor and inactivates it.
3. Repressor – lactose complex cannot bind with the operator gene, which is then turned on.
4. RNA polymerase transcribes all the structural genes to produce lac m-RNA which is then translated to produce all enzymes.
5. Thus, lactose acts as an inducer.
6. When the inducer level falls, the operator is blocked again by repressor and structural genes are repressed again. This is negative feedback.

1. In forensic science to solve rape and murder cases.
2. Finds out the biological father or mother or both, of the child, in case of disputed parentage.
3. Used in pedigree analysis in cats, dogs, horses and humans.

1. Genetic code is triplet, commaless and non-overlapping.
2. It is degenerate and non-ambiguous.
3. It is universal
4. It has polarity.

1. Ribosomes serve as site for protein synthesis.
2. A ribosome has one binding site for m-RNA and 3 binding sites for t-RNA. They are P-site (peptidylt-RNA-site), A-site (aminoacyl t-RNA-site) and E-site (exit site).
3. In Eukaryotes, a groove which is present between two subunits of ribosomes, protects the polypeptide chain from the action of cellular enzymes and also protects m-RNA from the action of nucleases.

1. Each single base is a part of only one codon.
2. Adjacent codons do not overlap.
3. If it had been overlapping type, with 6 bases, there would be 4 amino acid molecules in a chain.
4. Experimental evidence favours non-overlapping nature of genetic code.

1. In bacteria, m-RNA provides the encoded message for protein synthesis; t-RNA brings specific amino acid to the site of translation; r-RNA plays role in providing binding site to m-RNA and t-RNA.
2. There is single DNA dependent-RNA polymerase that catalyses transcription of all 3 types of RNA in bacteria.
3. RNA polymerase binds to promoter and initiates transcription (initiation) and synthesizes RNA.

1. HGP is associated with rapid development of Bioinformatics.
2. Knowledge gained about the functions of genes and proteins has a major impact in the fields like Medicine. Biotechnology and the Life sciences.
3. It has helped in identifying the genes that are associated with genetic characteristics.
4. The genetic basis of many hereditary diseases can be understood.
5. It has increased the understanding of gene structure and function in other species. As human beings have many of the genes same as those of flies, roundworms and mice, such studies will enhance understanding of human evolution.

Applications of genomics are as follows:

1. Structural and functional genomics is used in the improvement of crop plant, human health and livestock.
2. The knowledge and understanding acquired by genomics research can be applied in medicine, biotechnology and social sciences.
3. It helps in the treatment of genetic disorders through gene therapy.
4. It helps in the development of transgenic crops having desirable characters.
5. Genetic markers have applications in forensic analysis.
6. Genomics can lead to introduction of new gene in microbes to produce enzymes, therapeutic proteins and biofuels.

1. A set of genes will be switched on when a substrate is to be metabolized.
2. This phenomenon is called induction and small molecule responsible for this, is known as inducer.
3. It is positive control of gene regulation.
4. For example, lactose acts as an inducer in Lac operon.

Examples of coordinated regulation or expression of several sets of gene are:

1. If E.colt bacteria do not have lactose in the surrounding medium as a source of energy, then structural genes in Lac operon do not get transcribed and enzyme like β -galactosidase is not synthesized.
2. The development and differentiation of embryo into an adult organism.

1. Ribosomes serve as site for protein synthesis.
2. A ribosome has one binding site for m-RNA and 3 binding sites for t-RNA. They are P-site (peptidylt-RNA-site), A-site (aminoacyl t-RNA-site) and E-site (exit site).
3. In Eukaryotes, a groove which is present between two subunits of ribosomes, protects the polypeptide chain from the action of cellular enzymes and also protects m-RNA from the action of nucleases.

1. DNA regulates protein synthesis by coding for the specific sequence of amino acids in a protein.
2. This control is possible through transcription of m-RNA.
3. Genetic code is specific for particular amino acid.

1. About 20 different types of amino acids are required for protein synthesis.
2. They are available in the cytoplasm.

1. UAA, UAG and UGA are known as termination codons.
2. They do not code for any amino acid.
3. They terminate or stop the process of elongation of polypeptide chain.
4. Hence, they are known as termination codons.

a. Universal genetic code means that the specific codon codes for same amino acid in all living organisms, e.g. codon AUG always specifies amino acid methionine.

b. Genetic code is called non-ambiguous because, each codon specifies a particular amino acid.

1. In 1966, Crick proposed Wobble hypothesis.
2. According to this hypothesis, in codon- anticodon base pairing, the third base may not be complementary.
3. The third base of codon is called wobble base and this position is called wobble position.
4. This results in economy of t-RNA as anticodon of a t-RNA may bind with codon even when only first two bases are complementary.
5. For example, GUU, GUC, GUA and GUG codons code for amino acid Valine.
6. Degeneracy of genetic code means many codons can code for same amino acid.
7. Thus, the degeneracy of genetic code gets explained by Wobble hypothesis.

1. Each single base is a part of only one codon.
2. Adjacent codons do not overlap.
3. If it had been overlapping type, with 6 bases, there would be 4 amino acid molecules in a chain.
4. Experimental evidence favours non-overlapping nature of genetic code.

1. In bacteria, m-RNA provides the encoded message for protein synthesis; t-RNA brings specific amino acid to the site of translation; r-RNA plays role in providing binding site to m-RNA and t-RNA.
2. There is single DNA dependent-RNA polymerase that catalyses transcription of all 3 types of RNA in bacteria.
3. RNA polymerase binds to promoter and initiates transcription (initiation) and synthesizes RNA.

1. In each of the two daughter DNA molecules thus formed, one strand is parental and the other one is newly synthesized.
2. 50% is contributed by mother DNA.
3. Hence, DNA replication is described as semiconservative replication.

1. The lagging template is the template strand with free 5’ end.
2. The replication always starts at C-3 end of template strand and proceeds towards C-5 end.
3. Both the strands of the parental DNA are antiparallel and new strands are always formed in 5′ → 3′ direction, i.e. DNA polymerase synthesizes new strand in only one direction i.e. 5′ → 3′ direction.
4. Hence, the lagging templates becomes available for replication only discontinuously in small patches.
5. The new lagging strand develops discontinuously away from the replicating fork in the form of small Okazaki fragments.
6. Hence, Okazaki fragments formed on lagging strand only.

1. DNA regulates and controls all the cellular activities.
2. It replicates and gets distributed equally to the daughter cells when the cell divides.
3. It is a carrier of genetic information.
4. Heterocatalytic function : DNA directs the synthesis of chemical molecules other than itself. E.g. Synthesis of RNA (transcription), synthesis of protein (Translation), etc.
5. Autocatalytic function : DNA directs the synthesis of DNA itself. E.g. Replication.
6. DNA is a master molecule of a cell that initiates, guides, regulates and controls the process of protein synthesis.

1. Proteins play a significant role in the metabolism of living cells.
2. The actual phenotypic expression of living cells is dependent on the biochemical reactions.
3. Each biochemical reaction needs a specific enzyme for its initiation and completion. All the enzymes are proteins.
4. In a cell there are many structural proteins too. Thousands of structural and catalytic proteins are constantly required within the cell at all times.
5. Many functional proteins like hormones are also important for metabolism. Thus, for the synthesis of all such proteins, protein synthesis has become the most important and essential activity of the living cell.

1. It was believed that there are total 20 amino acids in the living world. But 21st amino acid called selenocysteine was discovered later.
2. This amino acid is coded by UGA which is usually a termination codon.
3. In both prokaryotic and eukaryotic cells polypeptide chains contain 100-300 amino acids and they are formed by specific arrangement of 21 amino acids.
4. But formation of selenocysteine requires the availability of element selenium in the cells.
5. Therefore, only 20 amino acids are considered as standard.

1. Griffith obtained live S-strain bacteria from the blood of the dead mice.
2. In a mixture of live R-bacteria and heat killed S-bacteria, live R-strain bacteria picked up something (transforming principle) from the heat-killed S bacterium and got changed into S-type.
3. Transforming principle allowed R-type bacteria to synthesize capsule and thus they became virulent.
4. Hence, on injecting a mixture of heat-killed S bacteria and live R bacteria, the mice died.

1. Proteins are large, complex molecules and store information required to govern cell metabolism. Hence it was assumed that variations found in species were caused by proteins.
2. On the other hand, DNA was considered as a small, simple molecule whose composition does not vary much among species.
3. Variations in the DNA molecules are different than the variation in shape, electrical charge and function shown by proteins.
4. Hence, initially proteins (and not DNA) were considered as genetic material.

1. In a typical mammalian cell, length of DNA double helix is approximately 2.2 metres.
2. The size of typical nucleus is approximately 10^-6 m
3. Such a long DNA molecule has to be fitted in small nuclear space.
4. Therefore, DNA is highly condensed, coiled and supercoiled so that it can be accommodated in the nucleus.