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Summary Chem exam
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Summary of 6 pages for the course Biology at 4 (Chem exam)
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Biotechnology and its ApplicationsGenetically 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 postharvest 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 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 antisense 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 proenzyme consists of 3 peptide chains − A, B, and C.
● Proenzyme insulin 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
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