Biotechnology And It's Application
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Biotechnology, as you would have learnt from the previous chapter, essentially deals with industrial scale production
of biopharmaceuticals and biologicals using genetically modified microbes, fungi, plants and animals. The
applications of biotechnology include therapeutics, diagnostics, genetically modified crops for agriculture, processed
food, bioremediation, waste treatment, and energy production.
(A) BIOTECHNOLOGICAL APPLICATION IN AGRICULTURE :
Let us take a look at the three options that can be thought for increasing food production
(i) agro-chemical based agriculture;
(ii) organic agriculture; and
(iii) genetically engineered crop-based agriculture.
The Green Revolution succeeded in tripling the food supply but yet it was not enough to feed the growing
human population. Increased yields have partly been due to the use of improved crop varieties, but mainly due
to the use of better management practices and use of agrochemicals (fertilisers and pesticides). However, for
farmers in the developing world, agrochemicals are often too expensive, and further increases in yield with
existing varieties are not possible using conventional breeding. Is there any alternative path that our under-
standing of genetics can show so that farmers may obtain maximum yield from their fields? Is there a way to
minimise the use of fertilisers and chemicals so that their harmful effects on the environment are reduced? Use
of genetically modified crops is a possible solution.
The Green Revolution succeeded in tripling the food supply but yet it was not enough to feed the growing
human population. Increased yields have partly been due to the use of improved crop varieties, but mainly due
to the use of better management practices and use of agrochemicals (fertilisers and pesticides). However, for
farmers in the developing world, agrochemicals are often too expensive, and further increases in yield with
existing varieties are not possible using conventional breeding. Is there any alternative path that our understand-
ing of genetics can show so that farmers may obtain maximum yield from their fields? Is there a way to minimise
the use of fertilisers and chemicals so that their harmful effects on the environment are reduced? Use of
genetically modified crops is a possible solution.
Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically
Modified Organisms (GMO).
GM has been used to create tailor-made plants to supply alternative resources to industries, in the form of
starches, fuels and pharmaceuticals.
Use of gentically modified (GM) plant :-
1. To enhance nutrientional quality of food
eg. Golden rice : Vitamin A enriched rice (In this rice gene of b-carotene is transfered)
2. Made crops more tolerant to abiotic stresses (cold, drought, salt, heat)
3. Helped to reduce post harvest losses
eg. Flavr Savr Tomato : Transgenic variety of Tomato – Flavr Savr due to the inhibition of polygalacturo-
nase enzyme which degrades pectin. So that tomato variety remains fresh and retain flavour much longer.
Flavr Savr Tomato develop by anti-sense tenchnology.
4. Increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil).
5. To produce biopharamaceutical product
eg. Production of Hirudin : Hirudin is a protein that prevents blood clotting. The gene incoding hirudin was
chemically synthesized and transferred into Brassica napus. Where hirudin accumulates in seeds. The hirudin
is purified and used as medicine.
6. To produce herbicide resistant plant
eg. First transgenic plant was tobacco. It contains resistant gene against weedicide (Glyphosate).
7. Pest-resistant crops : reduced reliance on chemical pesticides.
(i) Insect resistant plant
eg. 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 .
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.
Bacillus thuringiensis, produces crystal [Cry] protein. This Cry protein is toxic to Larvae of certain
insects. Each Cry protein is toxic to a different group of insects. The gene encoding cry protein is called
"cry gene". This Cry protein isolated and transferred into several crops. A crop expressing a cry gene is
usually resistant to the group of insects for which the concerned Cry protein is toxic. There are a number
of them, for example, the proteins encoded by the genes cryIAc and cryllAb control the cotton
bollworms, that of cryIAb controls corn borer.
However, gene symbol italics, e.g., cry. The first letter or the protein symbol, on the other hand, is always
capital and the symbol is always written in roman letters, e.g., Cry.
(ii) Nematode resistant plant :
Several nematodes parasitise 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 intro-
duction of DNA was such that it produced both sense and anti-sense RNA in the host cells. These two
RNA’s being complementary to each other formed a double stranded (dsRNA) that initiated RNAi and
thus, silenced the specific mRNA of the nematode. 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
Gene Therapy :
– A new system of medicine gene therapy, may develop to treat some hereditary diseases such as SCID, haemophilia
etc.
– Gene therapy is a collection of methods that allows correction of a gene defect that has been diagnosed in a
child/embryo. 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 into the individual or embryo to take over the function of and
compensate for the non-functional gene.
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.
Medical Diagnosis of Disease (Molecular diagnosis)
You know that for effective treatment of a disease, early diagnosis and understanding its pathophysiology is
very important. Using conventional methods of diagnosis (serum and urine analysis, etc.) early detection is not
possible. Recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-
sorbent Assay (ELISA) are some of the techniques that serve the purpose of early diagnosis.
Presence of a pathogen (bacteria, viruses, etc.) is normally suspected only when the pathogen has produced a
disease symptom. By this time the concentration of pathogen is already very high in the body. However, very
low concentration of a bacteria or virus (at a time when the symptoms of the disease are not yet visible) can be
detected by amplification of their nucleic acid by PCR. PCR is now routinely used to detect HIV in suspected
AIDS patients. It is being used to detect mutations in genes in suspected cancer patients too. It is a powerful
techqnique to identify many other genetic disorders.
A single stranded DNA or RNA, tagged with a radioactive molecule (probe) is allowed to hybridise to its
complementary DNA in a clone of cells followed by detection using autoradiography. The clone having the
mutated gene will hence not appear on the photographic film, because the probe will not have complimentarity
with the mutated gene.
ELISA is based on the principle of antigen-antibody interaction. Infection by pathogen can be detected by the
presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesised against the pathogen
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