DNA fingerprinting comes of age

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The paternity case concerning N.D. Tiwari underscores the potential of DNA technology across medical and other applications.

A file photo of the Centre for DNA Fingerprints and Diagnostics lab in Hyderabad. Few hospitals or diagnostic centres have ventured into DNA fingerprinting. — G. Krishnaswamy
A file photo of the Centre for DNA Fingerprints and Diagnostics lab in Hyderabad. Few hospitals or diagnostic centres have ventured into DNA fingerprinting. — G. Krishnaswamy

N.D. Tiwari, the maverick politician, managed to keep at bay the controversial issue of paternity for decades, using political clout, influence and delaying tactics in courts.

But, a few weeks ago, his lie was finally nailed by technology. DNA fingerprinting technology conclusively proved that the 87-year-old Tiwari, a former chief minister of Uttar Pradesh and Uttarakhand and more recently Governor of Andhra Pradesh, was indeed the biological father of 32-year-old Rohit Shekhar.

Rohit Shekhar filed a case five years ago. Tiwari tried his best to get it dismissed in court, going right up to the Supreme Court. He made valiant attempts to avoid the DNA (deoxyribonucleic acid) test, claiming invasion of his privacy.

But, the dogged pursuit by Rohit and the Court’s directive to get the blood sample for the test has finally brought out the truth. The acceptance of DNA fingerprinting as evidence by the courts should be seen as yet another milestone in the evolution of this technology in the country.

The first time that a court accepted DNA fingerprinting result to settle a paternity case was in 1991. It was the result of pioneering work by Lalji Singh and team at the Centre for Cellular and Molecular Biology (CCMB), Hyderabad, who had developed DNA fingerprinting technology in India.

The technique has been successfully deployed in solving some sensational crimes like the killing and roasting of the body of Naina Sahni in a tandoor in a New Delhi restaurant in 1995 as well as in the high profile assassinations of former Prime Minister Rajiv Gandhi and Punjab Chief Minister, Beant Singh. It has been used in identifying criminals, and sorting out immigration problems.

Untapped Potential

However, unlike in the US and the UK where it is available to the common man, in India its potential has not been exploited adequately, says Singh. In the last two decades, the applications of this technique have been widely demonstrated. It is possible to distinguish between the ivory of an Indian elephant and an African one, clear doubts on contamination of meat, establish the veracity of plant varieties and trace the source of snake venom.

Given the societal and business opportunities it has opened up, DNA fingerprinting should have been available as a simple, affordable test across the country. Efforts in building databanks of populations, screening for diseases, and general use of DNA technology for genetic counselling should have proliferated under a regulatory environment. But growth remains below expectations, say experts.

At present, the CCMB, the Centre for DNA Fingerprinting and Diagnostics (CDFD), and a few forensic laboratories have the DNA sequencers, diagnostic kits, laboratory facilities and trained manpower to undertake the testing. There are hardly any hospitals or diagnostic centres which have ventured into the area.

As a technology, DNA fingerprinting has emerged as a versatile scientific tool. During the early days, one required a few milligrams of the DNA sample for analysis, which took a couple of weeks. The availability of PCR (polymerase chain reaction) technology, automation and growing expertise has now made it possible to do a test in 24 hours. “We require a small (nanogram) sample of DNA, even degraded material is enough. The test is less expensive and accuracy beyond doubt”, Singh says. The significance lies in the accuracy of the analysis and ensuring quality and regulatory check on the use of the technique, he explains.

Explaining fingerprinting

Since the discovery of DNA by Watson and Crick in the 1950s, the understanding of these minute and fundamental structures has grown. The DNA of each individual is unique. It consists of 3 billion nucleotides. In 99.9 per cent of people, it is the same, but the miniscule or about 3 million nucleotides are unique to an individual. Every cell in a human body consists of the same set of DNA. By analysing the features in the small region of variation, it is possible to exactly identify the DNA fingerprint, which can then be matched according to the need.

A sample of blood, semen, root of hair, bone, or skin is needed to carry out the test. It is called a ‘fingerprint’ because no two individuals (except twins) will have the same DNA sequence.

DNA fingerprinting technology owes its origins to Alec Jeffrey, a British scientist. In India, Singh and his colleagues developed a slightly different probe called the Bkm-derived probe for DNA fingerprinting around 1988. It was isolated from the DNA of the female banded krait, a snake. Snakes are among the few species whose sex chromosomes are highly conserved.

Human, wildlife genetics

The insights into human DNA and genome sequence have given a push to the use of the DNA technology in human genetics. It is possible to predict the possible occurrence of genetic disorders like sickle cell anaemia, thalassaemia, Huntington’s disease, etc., at the pre-natal stage as well as counsel couples in advance. Similarly, in organ transplantation, the technique is being used to establish the relationship of donors clearly.

The major objective of the CDFD, carved out of the CCMN in 1995 is to develop, acquire and standardise protocols for carrier detection, prenatal diagnosis and genetic counselling for all genetic disorders in the country.

The Laboratory for the Conservation of Endangered Species (LaCONES), also in Hyderabad, is engaged in conservation of wildlife. It is developing, perhaps for the first time anywhere in the world, banks of semen, eggs, and embryos, facilities for artificial insemination and cloning of highly endangered species like lions, tigers, leopards, cheetah, etc.

The Centre has done extensive studies — from tiger census, genetic variations in the Indian tiger, the Asiatic lion and identifying the star tortoises (being smuggled out of India) to studying vultures.

An exciting area of application is in tracing the origin of human populations. Singh, Thangaraj and colleagues from the CCMB in collaboration with global institutions have thrown new light on the origin of man and Indian populations.

By studying the ‘Y’ chromosome, mitochondrial DNA and analysing large number of samples of different populations, they have come up with interesting insights. For example, one of their studies has been able to link the ancestry of the aboriginal tribes in Andaman and Nicobar islands — Onges, Great Andamanese, Nicobarese and Jarawas to early Africans.

Further studies have also established their genetic links to mainland Indians. In more recent studies, they have established the antecedents of the Aryans and Dravidians.

The challenge is to bring the fruits of these developments to the common man.

(This article was published on August 9, 2012)
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DNA testing today being carried out and being reported are just without any standards or guidelines. Unfortunately in many cases pending before the Courts, sub-quality DNA reports are being accepted without thorough scrutiny. DNA testing is governed by protocols, guidelines, validations. None of which are being followed either by CDFD or CCMB. I have served both the institutions and had always emphasised on inclusion of statistical data in the reports to include a DNA match. As a DNA expert I can say that not including a statistical calculation on an inclusion is unethical and any knowledgable defense expert would testify as to the correct calculation as well as the limitations of such a finding. Some laboratories are also giving a wrong impression as to the significance of the match. Although I do feel sorry for the technicians who are just following erroneous protocols imposed on them by their seniors. Issuing DNA reports by making it appear that the suspect fits the case is immoral.

from:  Dr G V Rao
Posted on: Aug 10, 2012 at 11:38 IST
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