With an example, explain how
biotechnology has been applied in each of
the following:
(a) In curing diabetes mellitus
(b) In raising pest resistant plants
(C) In producing more nutritionally
balanced milk.
Answers
Answer:
(a) Insulin consists of two short, polypeptide chains – chain A and B, linked via disulfide bridges. Insulin is produced as a ‘prohormone’ in mammals (including humans). This prohormone has an extra peptide, the C peptide, which needs to be removed to give rise to mature insulin.
The major challenge while generating human insulin is to assemble insulin into its mature form. An American company called ‘Eli Lilly’ overcame this hurdle in 1983. They prepared two DNA sequences that correspond to the A and B chains of human insulin. They then incorporated these sequences into plasmids of E. Coli to generate insulin chains. Further, they produced the chains separately, extracted and combined them by creating disulfide bonds to give rise to human insulin.
(b) Pest resistant plants are developed by using biotechnological processes.
A nematode Meloidogyne incognita infects the roots of tobacco plants, which reduces the production of tobacco.
RNA interference (RNAi) process is used for cellular defence. It involves silencing of a specific mRNA due to a complementary dsRNA. It occurs in all eukaryotic organisms as a method of cellular defense.
dsRNA binds 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.
Agrobacteriumvectors are used to introduce nematode-specific genes into the host plant. It produces both sense and anti-sens^e RNA in the host cells.
These two RNAs are complementary to each other and forms a double stranded RNA (rfsRNA) that initiate RNAi and hence, silence the specific mRNA of the nematode.
The parasite cannot survive in transgenic host, expressing specific interfering RNA. The transgenic plant thus, gets itself protected from the parasite.
(c) Animals that have had their DNA manipulated to possess and express an extra (foreign) gene are known as transgenic animals.
Transgenic rats, rabbits, pigs, sheep, cows and fish have been produced, although over 95 per cent of all existing transgenic animals are mice. They have numerous utilities.
Normal physiology and development: Transgenic animals can be specifically designed to allow the study of how genes are regulated, and how they affect the normal functions of the body and its development.
E.g. study of complex factors involved in growth such as insulin-like growth factor.
By introducing genes from other species that alter the formation of this factor and studying the biological effects that result, information is obtained about the biological role of the factor in the body.