Huge step forward

Human genome decoded completely

Published: Thursday 15 May 2003

-- for some, it was the logical outcome of more than a decade of intensive research. For others, it was the culmination of a mind-boggling journey through uncharted territory. Either way, the recent completion of the human genome project is seen as a landmark development. And the breakthrough couldn't have been better timed: it coincided with the 50th anniversary of the discovery of dna 's helical structure.

On April 14, 2003, the International Human Genome Consortium announced that it had completely decoded the set of instructions that govern how humans develop and function.

Hundreds of scientists in the consortium, representing 18 organisations in six countries, started the sequencing work in 1990. Less than three years after finishing the working draft of the human dna , and two years earlier than expected, the scientists announced that now, there were no substantial holes left in their knowledge of the string of units that determine our biology. Only about 1.5 per cent of the genome has not been decoded. These gaps are too costly to fill.

The genome is composed of about three billion pairs of dna chemicals within 24 chromosomes. The genes that control the body's functions are made of specific sequences of these chemical pairs. Scientists are still uncertain about how many genes there are in the genome. Many believe the number to be around 30,000. A surer estimate of this figure is expected to be arrived at with more research.

New treatments and earlier diagnosis of diseases are expected to be among the initial benefits of the sequencing. Allan Bradley, director of the Wellcome Trust Sanger Institute -- the British organisation that carried out almost one-third of the work -- states: "Just one part of the decoding -- the sequencing of chromosome 20 -- has already accelerated research for treating diabetes, leukaemia and eczema."

But for medicine, the challenge now is to move from ascertaining which genes cause a disease to knowing how to do something about the illness. For this, scientists would need to understand how sophisticated proteins -- the molecules that cells make from gene 'templates' -- work. The science of proteomics is still in its infancy.

The scientists have also identified more than 1.4 million snps (single nucleotide polymorphisms). snps are changes in the arrangement of dna letters that make people different from each other. They hold the key to susceptibility to diseases like cancer and diabetes, and individual responses to medication.

With the decoding, it may be possible to provide a unique sequence for each patient and then tailor therapies in accordance with the needs of the person. This could mitigate some of the side-effects caused by broad-spectrum drugs.

The us department of energy is using skills developed in the project to study the life processes of microbes. This, in turn, could lead to microbial solutions to control pollution and result in the development of energy sources.

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