12.2.3 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. Can you explain how PCR can detect very low
amounts of DNA? 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 complementarity 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.
Animals that have had their DNA manipulated to possess and express an
extra (foreign) gene are known as transgenic animals
. Transgenic rats,
rabbits, pigs, sheep, cows and fish have been produced, although over
95 per cent of all existing transgenic animals are mice. Why are these
animals being produced? How can man benefit from such modifications?
Let us try and explore some of the common reasons:
(i) Normal physiology and development: Transgenic animals can
be specifically designed to allow the study of how genes are
regulated, and how they affect the normal functions of the body
and its development, e.g., study of complex factors involved in growth
such as insulin-like growth factor. By introducing genes from other
species that alter the formation of this factor and studying the
biological effects that result, information is obtained about the
biological role of the factor in the body.
(ii) Study of disease: Many transgenic animals are designed to increase
our understanding of how genes contribute to the development of
disease. These are specially made to serve as models for human
diseases so that investigation of new treatments for diseases is made
possible. Today transgenic models exist for many human diseases
such as cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer’s.
(iii) Biological products:
Medicines required to treat certain human
diseases can contain biological products, but such products are
often expensive to make. Transgenic animals that produce useful
biological products can be created by the introduction of the portion
of DNA (or genes) which codes for a particular product such as
human protein (α-1-antitrypsin) used to treat emphysema. Similar
attempts are being made for treatment of phenylketonuria (PKU)
and cystic fibrosis. In 1997, the first transgenic cow, Rosie, produced
human protein-enriched milk (2.4 grams per litre). The milk
contained the human alpha-lactalbumin and was nutritionally a
more balanced product for human babies than natural cow-milk.
(iv) Vaccine safety: Transgenic mice are being developed for use in
testing the safety of vaccines before they are used on humans.
Transgenic mice are being used to test the safety of the polio vaccine.
If successful and found to be reliable, they could replace the use of
monkeys to test the safety of batches of the vaccine.
(v) Chemical safety testing: This is known as toxicity/safety testing.
The procedure is the same as that used for testing toxicity of drugs.
Transgenic animals are made that carry genes which make them more
sensitive to toxic substances than non-transgenic animals. They are
then exposed to the toxic substances and the effects studied. Toxicity
testing in such animals will allow us to obtain results in less time.
The manipulation of living organisms by the human race cannot go on
any further, without regulation. Some ethical standards are required to
evaluate the morality of all human activities that might help or harm living
Going beyond the morality of such issues, the biological significance
of such things is also important. Genetic modification of organisms can
have unpredicatable results when such organisms are introduced into
the ecosystem.
Therefore, the Indian Government has set up organisations such as
GEAC (Genetic Engineering Approval Committee), which will make
decisions regarding the validity of GM research and the safety of
introducing GM-organisms for public services.
The modification/usage of living organisms for public services (as food
and medicine sources, for example) has also created problems with patents
granted for the same.
There is growing public anger that certain companies are being
granted patents for products and technologies that make use of the
genetic materials, plants and other biological resources that have long
been identified, developed and used by farmers and indigenous people
of a specific region/country.
Rice is an important food grain, the presence of which goes back
thousands of years in Asia’s agricultural history. There are an estimated
200,000 varieties of rice in India alone. The diversity of rice in India is
one of the richest in the world. Basmati rice is distinct for its unique
aroma and flavour and 27 documented varieties of Basmati are grown
in India. There is reference to Basmati in ancient texts, folklore and
poetry, as it has been grown for centuries. In 1997, an American
company got patent rights on Basmati rice through the US Patent and
Trademark Office. This allowed the company to sell a ‘new’ variety of
Basmati, in the US and abroad. This ‘new’ variety of Basmati had actually
been derived from Indian farmer’s varieties. Indian Basmati was crossed
with semi-dwarf varieties and claimed as an invention or a novelty. The
patent extends to functional equivalents, implying that other people
selling Basmati rice could be restricted by the patent. Several attempts
have also been made to patent uses, products and processes based on
Indian traditional herbal medicines, e.g., turmeric neem. If we are not
vigilant and we do not immediately counter these patent applications,
other countries/individuals may encash on our rich legacy and we may
not be able to do anything about it.
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-resour
ces. 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
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
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.