The critical areas of biotechnology are:
- Providing the best catalyst in the form of improved organism usually a microbe or pure enzyme.
- Creating optimal condition through engineering for a catalyst to act.
- Downstream processing technologies to purify the protein/organic compound.
BIOTECHNOLOGICAL APPLICATIONS IN AGRICULTURE:
- Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO).
- Advantages of Genetic Modification in plants.
- Made crops more tolerant to abiotic stresses (cold, drought, salt, heat)
- Reduce reliance on chemical pesticides (pest resistant crop)
- Helped to reduce post harvest losses.
- Increased efficiency of mineral usage by plants.
- Enhanced nutritional values of food e.g. vitamin A enriched rice.
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.
- These proteins are present in inactive protoxin form, but become active toxin in the alkaline pH of insect gut.
- The activated toxin binds to the surface of midgut epithelial cells and create pores that cause cell swelling and lysis and eventually cause death of insect
- Specific Bt toxin genes were isolated form B. thuringiensis and genetically transferred to several plants such as cotton.
- Crystal proteins are produced by a gene called cry in B. thuringiensis.
- The protein coded by genes cryIAc and cryIIAb control the cotton bollworms.
- The protein coded by gene cryIAb controls corn borer.
Pest resistant plants:
- Several nematodes parasitize a wide variety of plants and animals including human beings.
- A nematode Meloidegyne incognitia infects the root of tobacco plants and causes a great reduction in yield.
- Strategy based on RNA interference (RNAi) prevents this infestation.
- Process by which double-stranded RNA (dsRNA) directs sequence-specific degradation of mRNA
Steps of RNA interference:
- Double stranded RNA is produced endogenously or exogenously.
- Using Agrobacterium vectors nematode specific genes were introduced into the host plant (tobacco plant).
- Introduction of DNA produces both sense and antisense RNA in the host.
- These two RNA’s being complementary to each other formed a double stranded (dsRNA) that initiated RNAi.
- The dsRNA injected into the host plant from outside called exogenous dsRNA.
- The dsRNAs are cleaved into 21-23 nt segments (“small interfering RNAs”, or siRNAs) by an enzyme called Dicer.
- siRNAs are incorporated into RNA-induced silencing complex (RISC)
- Guided by base complementarity of the siRNA, the RISC targets mRNA for degradation.
- The consequence was that the parasite could not survive in a transgenic host.
BIOTECHNOLOGICAL APPLICATIONS IN MEDICINE:
- Biotechnology enables mass production of safe and more effective therapeutic drugs.
- Recombinant therapeutics does not induce unwanted immunological responses as is common in case of similar products isolated from non-human sources.
- At present around 30 recombinant therapeutics, approved for human-use.
Genetically Engineered Insulin:
- Taking insulin at regular interval of time is required for adult-onset diabetes.
- Previously the source of insulin was the slaughtered cattle and pigs.
- This insulin caused allergy in some patients.
- Each insulin made of two short polypeptide chains; chain A and chain B that are linked together by disulphide linkage.
- Insulin synthesized in pancreas as pro-hormone which is a single polypeptide with an extra stretch called C-peptide.
- C-peptide is removed during matured insulin.
- 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.
- Chain A and chain B produced separately, extracted and combined by creating disulfide bonds to form mature human insulin.
CBSE Biology (Chapter Wise) Class XII ( By Mr. Hare Krushna Giri )
Email Id : [email protected]
