BIOLOGY 3 Marks Question

→ Gene therapy is a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo.
→ Here by using DNA medicinal protein is produce which correct or treat the mutated Gene.
→ Here genes are inserted into a person's cells and tissues to treat a disease.
→ Correction of a genetic defect involves delivery of a normal gene in to the individual or embryo. to take over the function of and compensate for the non-functional gene.
→ Example- Adenosine deaminase deficiency
→ The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency.
→ This enzyme is crucial for the immune system to function.
→ The disorder is caused due to the deletion of the gene for adenosine deaminase.
→ In some children ADA deficiency can be cured by bone marrow transplantation.
→ In others it can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection.
→ But the problem with both of these approaches that they are not completely curative. As a first step towards gene therapy, lymphocytes from the blood of the patient are grown in a culture outside the body.
→ A functional ADA CDNA (using a retroviral vector) is then introduced into these lymphocytes, which are subsequently returned to the patient.
→ However, as these cells are not immortal, the patient requires periodic infusion of such genetically engineered lymphocytes.
→ However, if the gene isolate from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.

→ Several nematodes parasites a wide variety of plants and animals including human beings.
→ A nematode Meloidegyne incognitia infects the roots of tobacco plants and causes a great reduction in yield.
→ A novel strategy was adopted to prevent this infestation which was based on the process of RNA interference (RNAi).
→ RNAi takes place in all eukaryotic organisms as a method of cellular defense.
→ This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to 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.
→ Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant.
→ The introduction of DNA was such that it produced both sense and anti-sense RNA in the hostcells.
→ These two RNA's being complementary to each other formed a double stranded (dsRNA) that initiated RNAi and thus, silenced the specific mRNA of then ematode.
→ The consequence was that the parasite could not survive in a transgenic host expressing specific interfering RNA.
→ The transgenic plant therefore got itself protected from the parasite.

→ In Bacillus thuringiensis, there is a bacterial gene which produce toxic crystal protein having insecticidal activity. This crystal protein is called Cry protein.
→ Bt toxin is produced by a bacterium called Bacillus thuringiensis.
→ Bt toxin gene has been cloned from the bacteria and been expressed in plants.
→ So plants become resistance to insects without the need for insecticides. This is how a biopesticide is created.
→ 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.
→ Actually, the Bt toxin protein exist as inactive protoxins.
→ But once an insect ingest the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilise the crystals.
→ 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 the insect.
→ Specific Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton.
→ The proteins encoded by the genes crylAc and cryllAb control the cotton bollworms.
→ CrylAb controls corn borer.

→ Insulin is produced by beta cells of pancreas.
→ Insulin plays important role in a sugar or carbohydrate metabolism.
→ Due to lack of insulin diabetes mellitus occurs in humans.
→ Insulin used for diabetes was earlier extracted from pancreas of slaughtered cattle and pigs.
→ Insulin from an animal source, though caused some patients to develop allergy or other types of reactions to the foreign protein.

→ Insulin consists of two short polypeptide chains: chain A and chain B.
→ Polypeptide Chain A contains 21 amino acids and chain B contains 30 amino acids that are linked together by disulphide bridges.
→ In mammals, including humans, insulin is synthesised as a pro-hormone (like a pro-enzyme, the pro-hormone also needs to be processed before it becomes a fully mature and functional hormone) which contains an extra stretch called the C peptide.
→ This C peptide is not present in the mature insulin and is removed during maturation into insulin.
→ The main challenge for production of insulin using rDNA techniques was getting insulin assembled into a mature form.
→ 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.
→ Chains A and B were produced separately, extracted and combined by creating disulfide bonds to form human insulin.

→ Biopiracy is the term used to refer to the use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned without compensatory payment.
→ Most of the industrialised nations are rich financially but poor in biodiversity and traditional knowledge.
→ In contrast the developing and the underdeveloped world is rich in biodiversity and traditional knowledge related to bio-resources.
→ Traditional knowledge related to bio-resources can be exploited to develop modern applications and can also be used to save time, effort and expenditure during their commercialisation.
→ There has been growing realisation of the injustice, inadequate compensation and benefit sharing between developed and developing countries.
→ Therefore, some nations are developing laws to prevent such unauthorised exploitation of their bio-resources and traditional knowledge.
→ The Indian Parliament has recently cleared the second amendment of the Indian Patents Bill, that takes such issues into consideration, including patent terms, emergency provisions and research and development initiative.