The human genome project was started in 1988 as a world wide endeavour to analyse the sequence of DNA present within the nucleus and therby characterize the genetic make up of human beings. In parallel, efforts were also launched to carry out similar studies on other lower organisms to allow comparative analysis.

Genes are composed of a sequence of deoxyribonucleic acids (or DNA). It is this sequence which defines the information content of the genes. These genes provide instructions for making proteins, which themselves are complicated biological molecules that perform a multitude of cellular functions including building tissues, metabolism and fighting diseases. The research on elucidating the function of proteins within the cell forms another branch of current interest known as "proteomics".

Considering the fact that human beings are the most evolved species on this planet it would be natural to believe that they may have a very complicated genetic constitution and hence require a larger number of genes to perform various functions. However, surprisingly, human beings seem to have only about 30,000 genes which is about twice the number as in a fly or worm and only five time as many as in a primitive single celled bacterium. This is far below the earlier estimated number of more than 100,000.

At least 223 human genes appear to have come from bacteria that infected our ancestors several million years ago. Some of these genes now perform useful tasks such as producing chemicals necessary for healthy brain function. As remarked by David Baltimore, a geneticist at the California Institute of Technology in Pasadena, in the scientific journal Nature - "We have many fewer genes than might have been expected for a relatively complex organism,". Thus a few genes can produce the far greater number of proteins that a human being may require for normal function.Several reports note that genes can be sliced and combined in various ways, at different times and in different organs,to produce 10 or more different proteins. This could then account for the greater level of complexity achieved through a smaller number of basic building blocks. To quote Venter -"Gene number does not correlate with complexity. Rather it is the interactions within and among these sets that result in such great variations." The unexpectedly small number of genes that determine the genetic makeup of every man, woman and child is one of the most intriguing findings of this project.

This unbiased genomic analysis, which is based on DNA from both sexes and from people of African,Asian, Hispanic and European descent, showed up other interesting trends. It appears that there is a remarkable unity in the genetic composition of human beings regardless of race, gender or nationality.Each person seems to share nearly 99.99 percent of his or her genetic code with every other person. Also, people from different racial groups may have more in common genetically than people within the same race. Svante Paabo, a German expert on evolutionary genetics says "It is clear that what is called `race,' although culturally important, reflects just a few traits determined by a tiny fraction of our genes".

One of the greatest contribution of this project would be towards understanding various diseases especially those related directly to defects in chromosomes (which are long stretches of dna composed of various genes).With the help of this new resource, researchers studying a disease associated with detectable defects on a chromosome can identify the precise DNA segment involved, then order normal copies of the segment for further analysis in their own laboratories. This resource will enable researchers to identify the genes that are defective in a large number of genetic diseases, Researchers investigating cancers,developmental disorders and multisystem genetic diseases often directly observe abnormal band patterns and other microscopic aberrations in a patient's chromosomes.

In addition, laboratory tools such as fluorescent tags may detect a translocation, an abnormal exchange of DNA between chromosomes. According to a Nature paper by David Valle of the Johns Hopkins School of Medicine in Baltimore researchers have compiled a list of nearly 923 genes associated with various diseases.The genome sequence is beginning to help scientists understand the genetic factors underlying addiction to alcohol and drugs, but no specific genes have been identified as yet.Unfortunately, the link between genes and disease is extremely complex and efforts to cure diseases by tinkering with genes have so far not been very successful.

Lastly, several authors do throw in a word of caution that human health, behavior and characteristics may be influenced by many factors which may not be necessarily 'genetic'. So-called genetic determinism -the idea that a person's characteristics are "hard-wired" -may be a fallacy and should be taken with a pinch of salt. Environmental factors such as home, schooling, friends and general lifestyle may have a far greater impact on personality and well-being.

It is important to understand that the present knowledge forms just the tip of the ice berg.What lies ahead is the far more challenging effort to try and understand the function of each of the 30,000 genes, which may take up the better part of this century.......

*The Figures Appearing in this Article are From CCMB, Hydrabad, India
*Article From CCMB will appear in Forthcoming issues
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