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Genetically Engineered Crops
● Genetically engineered crops have desirable genes (as of insect/pest
resistance, giving better yield) incorporated in them.
● Genetically modified crops have
○ more tolerance to abiotic stresses such as cold, drought, salinity,
heat, etc.
○ insect/pest resistance
○ reduced post-harvest losses
○ efficient mineral usage by plants
○ enhanced nutritional value (e.g., Vitamin A rich rice)
Bt Cotton
● Bacillus thuringiensis is a bacterium that produces proteins to kill
certain insects such as lepidopterans (armyworm), coleopterans
(beetles), and dipterans (flies/ mosquitoes). B. thuringiensis produces
a protein crystal containing a toxic protein (inactivated state).
● Inactivated toxin Activated in the presence of Alkaline PH activated toxin (gut of insect)
● Activated toxin binds to the epithelial cells in the midgut of insect and
creates pores that cause lyses and swelling and eventually death of
insect.
● This toxin is encoded by a gene called Cry in the bacterium. Genes
encoded by Cry IAc and Cry II Ab control cotton bollworms and those
encoded by Cry IAb control corn borer.
● Cry genes are introduced into the cotton plants to produce Bt cotton,
which is an insect resistant variety of cotton.
RNA Interference (RNAi)
● RNAi is a method adopted to prevent infestation of roots of tobacco
plants by a nematode Meloidegyne incognitia.
● In RNAi, a complementary RNA binds to mRNA to form a ds RNA,
which cannot translate and hence, its expression is blocked
(Silencing).
● This complementary mRNA may come from
○ infection by RNA viruses
○ transposons (mobile genetic elements)
● RNAi exists naturally in eukaryotes as a method of cellular defence.
● Nematode specific genes (DNA) were introduced in the host plant.
● The introduced DNA forms both sense and anti-sense RNA.
● Two strands being complementary to each other bend and form ds
RNA, leading to RNAi.
● mRNA of nematode is silenced and the parasite cannot survive in the
transgenic host.
Applications of Biotechnology in Medicine
Recombinant Therapeutics
● With the help of RDT, mass production of efficient therapeutic drugs
can be accomplished.
● These are safe and do not induce unwanted immunological response.
Genetically Engineered Insulin
● Insulin is in great demand due to increase in number of patients with
adult onset diabetes.
● Insulin extracted from animal source (example, slaughtered cattle and
pigs) induce allergy in humans.
● Insulin as a pro-enzyme consists of 3 peptide chains − A, B, and C.
● Pro-enzyme insulin by the removal of C peptide gets Converted into Mature insulin
● Mature insulin consists of only two peptide chains − A and B. Both these chains
were separately isolated and introduced in plasmids of E. coli to produce
insulin chains.
● Separately produced chains A and B were extracted and combined by
creating a disulphide bond to form mature human insulin.
Gene Therapy
● Gene therapy is an attempt to deal with genetic or congenital diseases.
● This aims at correction of a genetic defect by delivery of a normal gene
into an individual or embryo to take over or compensate the function
for a non-functional gene.
● The first disease to have a gene therapy is ADA (Adenosine
deaminase) deficiency. In this, the gene coding for enzyme ADA gets
deleted leading to deficiency of ADA and problems in immune system.
● ADA deficiency can also be treated with:
○ Bone marrow transplantation
○ Enzyme replacement therapy
● Gene therapy for ADA deficiency:
○ Lymphocytes isolated from patient’s blood are cultured in-vitro.
○ Functional ADA cDNA are then introduced into the cultured
lymphocytes.
○ These lymphocytes are returned back to the patient’s body.
● Lymphocytes are not immortal. Therefore, repeated infusion of
genetically engineered lymphocytes is required.
● Permanent cure − Introduction of gene isolated from bone marrow cells
producing ADA into cells at early embryonic stages
Molecular Diagnosis
● Recombinant DNA technologies, PCR, ELISA (enzyme linked immuno
sorbent assay) are some of the technologies of molecular diagnosis.
● Early diagnosis of bacteria and virus in body, when the concentration
is extremely low, can be done by PCR since it amplifies the DNA
several folds.
● PCR is used to detect HIV virus in suspected AIDS patients and
mutations in genes in suspected cancer patients.
● ELISA is based on antigen-antibody interactions. In the presence of an
antigen, the antibody produced against it can be detected.
● Hybridisation with a radioactive probe − In this approach, gene is hybridized with
a radioactive probe and autoradiography is used for detection. The regions where
mutation is present in the gene will not appear in the photographic film since
probe will not be able to bind with that part.
Transgenic Animals & Biopiracy
Transgenic Animals
● Animals that have their DNA manipulated to possess or express an
extra gene are called transgenic animals.
● Till date, transgenic rats, rabbits, pigs, sheep, cows, and fish have
been produced.
Reasons for Producing Transgenic Animals
● Study of normal physiology
○ Transgenic animals serve as models to study genetics, regulation
and down regulation of genes, and their corresponding effects on
physiology.
○ They give information about the biological role of a particular
factor in the body.
● Study of diseases
○ They act as models to study genetic basis of diseases.
○ These studies aid in finding possible treatments of diseases.
○ Transgenic models exist of various human diseases such as
cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer’s, etc.
● Biological products
○ Treatment of diseases often requires certain products that are
expensive to make.
○ Transgenic animals can be produced that have genes, coding for
that particular product.
○ Example − Human protein α-1-antitrypsim used to treat emphysema is
isolated by this method.
○ In 1997, first transgenic cow Rosie produced human proteinenriched
milk, which contained α-lactalbumin and was
nutritionally more suitable for human babies.
● Vaccine safety tests
○ Transgenic mice are used to test vaccines for their safety before
they are used for humans.
○ Example − Transgenic mice are used to check polio vaccines.
● Chemical safety testing
○ Transgenic animals contain genes that make them more
sensitive to toxic substances than non-transgenic.
○ Toxicity testing in such animals helps us to obtain results in less
time.
Ethical Issues Associated with Transgenic Animals
● Indian government has set up an organization GEAC (Genetic
Engineering Approval Committee), which makes decisions regarding
validity of GM research and its use for public utility.
● Modification which may result in the loss of biological significance of
animals cannot go beyond regulation.
● Unpredictable results may be observed, if these organisms are
introduced in natural ecosystem.
● Patents for transgenic varieties also create problems as many
indigenous varieties are claimed by multinational companies as their
own inventions.
● For example − A new variety of Basmati was claimed by an American company
through patenting. This new variety was actually derived by Indian farmers by
crossing Indian Basmati with semi-dwarf varieties.
● Similarly Neem and turmeric, which have been used for ages in Indian
medicines, are also matters of dispute for patent rights.
Biopiracy
● Use of bio-resources by MNCs and other organisations without proper
authorisation from countries and people concerned without
compensatory payment
● Industrialized and developed nations are economically rich, but poor in
biodiversity while opposite prevails for developing nations. Therefore,
developed countries exploit traditional knowledge and resources of
poor countries for commercialisation.
● This is a matter of injustice since inadequate compensation and benefit
sharing is given to poor countries in return. Therefore, steps should be
taken by developing countries to prevent this exploitation.
● The Indian parliament has recently introduced second amendment of
Indian patents bill to deal with these issues.
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