Human Genome Project – Importance and Objectives

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Human Genome Project – Importance and Objectives. Pushpa M. Bhargava, The Hindu, Oct. 26, 2000.

THE RECENT announcement of the virtual completion of the human genome sequencing project is regarded as an important advancement. (The term, genome, refers to the total unit genetic material – that is DNA – of the organism.)

This project was begun nearly 12 years ago under the initial sponsorship of the Department of Energy and then the National Institutes of Health of the U.S. It was, at that time, estimated to cost about three billion dollars.

Although this has been a remarkable achievement and successful culmination of one of the largest world-wide team efforts ever made in science – an effort which extended over a period of over a dozen years – it is primarily a technological achievement, comparable to the first man-made satellite in space, the first manned space flight, and the first landing of man on moon.

The genomes of some 30 other organisms have been sequenced since the work started on the human genome project; these include the common bacterium, E.coli Haemophilus influenzae which causes influenza, the fruit fly, and the nematode, C.elegans. It is just that the human genome is vastly bigger than all the other genomes sequenced so far, taken together.

Let us first comprehend and appreciate the magnitude of the job that our scientists have accomplished, with only less than 3 per cent of the genome yet remaining to be sequenced. A 500-page book of normal size, with about 45 lines on each page and 80 letters (including spaces) in each line, would mean space for 1.8 million letters in the book.

The human genome has six billion such letters; it is in fact nothing but a pair of strings of four building blocks abbreviated as A, T, G and C, arranged in a specific sequence in each string; a part of this sequence differs from individual to individual.

The two strings – or strands as they are generally called – are coiled around each other as in a double helix. There are three billion building blocks in each of the two strings.

Since wherever there is A in one stand, there is T in the other, and wherever there is G in our strand, there is C in the other, we only need to sequence three billion of these building blocks in one string, as the pair rule will allow us to know the sequence of the other three billion on the second string, once the sequence of the first string is known.At the rate of 1.8 million letters in a book of 500 pages, one would need 1667 books for putting together all the information in the human genome residing in the sequence of the four building blocks; it is this information that is responsible – totally and wholly – for what we are and how we may respond to the environment.

There will not be many publishers in the world who bring out each year 1667 new books of 500 pages each!

One may now ask as to why did scientists embark on such a mega project. We should first recognise that it was this project that set up the environment for sequencing the genomes of other living organisms that I have mentioned above.

The bacterium Helicobacter pylori was shown some five years ago to be the major causative agent for stomach ulcers which affect some four per cent of our population. This organism causes the disease by attaching itself to the cells of the intestinal epitheliums.

A technique called differential genome analysis has shown that 123 proteins of the bacterium are involved in the above attachment.

This knowledge gives us an opening to design new drugs which would prevent the attachment of specific proteins to the intestinal cells, which attachment is essential for the disease to be caused.

It is similarly expected that when we have the sequence of the genome of the malaria- causing parasite we would have at least 18 new approaches towards designing effective antimalarial drugs. Availability of sequence of the genetic material – that is DNA – of human beings will allow us to obtain a potential disease- profile of individuals, even before birth: what diseases, if any, the individual would definitely suffer in the future and what diseases he may suffer with defined probabilities.

There are some five thousand genetic or inheritable diseases already known and, perhaps, another five thousand remaining to be discovered.

The availability of human genome sequence makes it possible – even probable – that within a few years we would be able to screen an individual, before or after birth, for all these diseases at one go and at a reasonable cost. We also have genes for susceptibility to certain diseases – for example – to one type of diabetes. This means that out of two persons who have the gene, one may get the disease while the other would not.

Today, we can state the probability of one who has the gene, actually becoming diseased, only on the basis of empirical analysis of existing data.

Studies over a period will now make it possible for scientists to define environmental conditions, including nutrition and other life-style factors, which would make a person who is genetically susceptible to a disease, actually become diseased.

Similarly, one would begin to understand the nature of genetic differences between individual and between social or ethnic groups, and the significance, if any, of these differences.

This information, combined with genetic engineering technologies, would give us a new tool for social engineering, and thus a whole range of new choices and a new exciting area for us to demonstrate our wisdom.

The origin of viruses, for example of human viruses, has been an enigma. The formation in human genome may make it possible to have answers to this intellectually exciting and practically important question. what we already know is that our genome has stretches of DNA of which the sequence is very similar to what is found in many disease-causing viruses.

Recent work has shown that there are minor genetic difference between identical twins. The availability of techniques to compare human genome sequences will allow us to map these differences and understand the nature and pattern of genetic evolution, if any, during development in utero.

Sequences of the genetic material (DNA) of special organisms such as radiation-resistant bacteria (one of which has just been sequenced), or heat tolerant, salt tolerant or cold tolerant bacteria, could give us clues to the mechanisms of such tolerance; this would in turn help us identify the right environment to combat certain genetic weaknesses.

So far the scientists have no inkling whatsoever of the function of over 95 per cent of the DNA in our genome. This has persuaded scientists to call it “junk DNA”. Many of us believe that this is simply a manifestation of our lack of understanding the ways of Nature which is far more clever than us.

The availability of the genome sequences of human beings would, in course of time, surely tell us something about the function of this, so-called junk DNA.

But these obvious uses of human genome sequence data would be just a tiny part of the tip of a massive iceberg. Much of biology in the next few decades will be dominated by scientists discovering new uses of human and other genomic sequence data.

These analyses would require an intimate and lasting marriage of molecular biology and information technology.

Pushpa M. Bhargava

Former Director, Centre for Cellular and Molecular Biology, Hyderabad, AP

(To be continued)

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Human Genome Project – Importance and Objectives. Pushpa M. Bhargava, The Hindu, Oct. 26, 2000.

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