Quiz 3: The Biological Basis of Life


Deoxyribonucleic acid (DNA) is the hereditary material that is found in all living cells that carry the information required for the production of proteins. The information is stored in the form of polynucleic acid sequences called genes. These proteins, in turn, are responsible for the structure and development of the organism. Before the discovery of DNA, it was not possible to ascertain the origin of species. The theory of evolution gained more credibility over the decades following the discovery of DNA with the advent of modern sequencing technologies. DNA was the missing piece of evidence which made it possible to connect all the species on earth. All the organisms share genes. Mutations in these genes are one of the chief driving factors in the evolution of new species. Moreover, experiments involving DNA have found that homologous genes exist throughout the kingdom of life. For example, if the gene responsible for the production of protein 'X' was to be excised from one organism and introduced into the genome of an entirely different organism, the gene would still produce protein 'X'. This can be taken as proof that the mechanisms regulating gene expression are similar in all living cells. Discrete forms of life like a bacterial cell and a mammalian cell share the same DNA, albeit with differences in the number of the genes. The closest living relatives of humans, the chimpanzees, share 97% of genes.

Proteins are polypeptides that serve as building blocks of the body. The core structures of proteins are same in all the organisms. For example, all proteins are polymers of amino acids and they exhibit either one of the two configurations, including the alpha helix or the beta sheets. The protein structure and function is determined by the amino acid sequence, which in turn is determined by the gene sequence. Therefore, any change in the gene sequence due to mutation can affect the protein structure. Homologous gene sequences in different species have arisen due to the occurrence of mutations in genes, which then lead to divergence and gradual evolution of a new species. The new species, therefore, shares protein structural and functional similarity with its ancestors. Recent advances in proteomics have made it possible to identify structurally similar proteins in different species, which have the same function. Even within the same species, changes in amino acid composition can lead to minor differences in protein, giving rise to various isoforms, all of, which may have the same function. From an anthropological viewpoint, studying the protein sequence, structure and function are helpful is charting out the relationships between various species, and helping in constructing a phylogenetic tree. It can help biologists to analyze the origin of different proteins, their role in different organisms, the passing of these traits from one generation to another and how new protein arise. These can answer some of the fundamental questions concerning the evolution of species.

Cloning is a process of producing exact genetic copies of the organism. These identical copies of organism produced are known as Clones. They can be produced either naturally or artificially. DNA (deoxyribonucleic acid) of the identical clones produced is identical. They are genetically similar in shape, size and organization. Cloning techniques have made easier to deal with various problems occurring in the life of the body. Dolly is a name given to a sheep which was the first mammal to be cloned from a somatic cell. The cell was taken from the mammary gland. This was done in Roslin Institute, Scotland. Cloning has the following benefits : 1. It is beneficial in treatment of various diseases. For example, cancer can be treated with the help of gene cloning. The desired gene is taken out from the cell, cloned and transplanted again. 2. It has made scientists to produce the damaged organs and then re-transplant them in the body. 3. The endangered species can be saved by cloning. 4. Many vaccines are produced through cloning. 5. This technique is very useful for infertile couples. There are various living species which are used for cloning. They are cow, mule, sheep, monkey, mice and many more. These species are cloned at a very high rate which gives rise to uncertainty in the population and disbalance of the nature. Therefore, cloning should be restricted only to a certain species. There is a risk of mutation because Cloning genetically modifies the DNA (deoxyribonucleic acid), giving rise to abnormalities in the cloned species. It also leads in development of new diseases. Also, there are many legal and civil problems which arise due to use of cloning techniques. Cloning destroy the uniqueness of the particular species. Pet cloning will give rise to new pet which would be undistinguishable from the old one. Hence, it will very difficult to recognize them. The attention which would be given to the only older pet will now be divided between both of them. It will lead to exploitation of the individuality. Therefore, the idea of pet cloning is not that worth to exhibit. Every individual is born unique and cloning exploit the uniqueness of the individual.