12. BIOTECHNOLOGY AND ITS APPLICATIONS
APPLICATIONS IN MEDICINE
- Recombinant DNA technology helps for
mass production of safe and more effective therapeutic drugs.
- Products from non-human sources cause
unwanted immunological responses. But recombinant therapeutics does not have
such problems.
- At present, about 30 recombinant
therapeutics have been approved. Of these, 12 are being marketed in India.
1. Genetically Engineered Insulin
- Insulin is used to manage
adult-onset diabetes.
- Insulin from
the pancreas of animals (cattle & pigs) causes allergy or other types of
reactions to the foreign protein.
- Now, it is
possible to produce human insulin using bacteria.
- Insulin consists of two short
polypeptide chains (chain A & chain B) that are linked by disulphide
bridges.
-
- The pro-hormone contains an extra
stretch called C peptide. This is removed during maturation into
insulin.
- In 1983, Eli Lilly (an
American company) prepared two DNA sequences corresponding to A & B chains
of human insulin and introduced them in plasmids of E. coli to produce
insulin chains. Chains A & B were combined by creating disulfide bonds to
form human insulin (Humulin).
2. Gene Therapy
- It is a method to correct a gene
defect in a child/embryo.
- Here, genes are inserted into a
person’s cells and tissues to treat a hereditary disease. It compensates for
the non-functional gene.
- First clinical gene therapy (1990) was
given to a 4-year old girl with adenosine deaminase (ADA)
deficiency.
- This is caused due to the deletion
of a gene of adenosine deaminase (an enzyme for the functioning
of immune system). It can be cured by bone marrow transplantation or by
enzyme replacement therapy (injection of ADA). But these are not completely
curative.
- Gene therapy
for ADA deficiency: Collect lymphocytes from the
patient’s blood and grow in a culture → Introduce a functional ADA cDNA into
lymphocytes (using a retroviral vector) → They are returned to the patient.
This should be periodically repeated
as lymphocytes are not immortal.
- If the
ADA gene from marrow cells is introduced into cells at early
embryonic stages, it could be a permanent cure.
3. Molecular Diagnosis
-
Conventional methods (serum & urine analysis)
are not suitable for early diagnosis of diseases.
- It is possible by techniques such as Recombinant DNA
technology, PCR & ELISA.
PCR (Polymerase Chain Reaction):
- Presence of a pathogen is normally
suspected only based on symptoms. By this time, the concentration of pathogen
is already very high in the body.
- However, very low concentration of a
bacteria or virus can be detected by amplification of their nucleic acid by
PCR.
- Uses of PCR:
o
To detect HIV in suspected patients.
o
To detect gene mutations in
suspected cancer patients.
o
To identify many other genetic
disorders.
- A single stranded DNA or RNA, tagged
with a radioactive molecule (probe) is hybridized to its complementary DNA in a
clone of cells. It is detected by autoradiography. The clone having mutated
gene will not appear on photographic film, because the probe will not have complementarity
with mutated gene.
ELISA (Enzyme Linked Immuno-Sorbent
Assay):
- It is based on antigen-antibody
interaction.
- Infection by pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesized against the pathogen.