Genetics

17 April 2008

Genome breakthrough a milestone

The idea of having your personal genetic code unravelled was once a dream reserved for individuals who were fans of science or big on ego - and deep in pocket.

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The idea of having your personal genetic code unravelled was once a dream reserved for individuals who were fans of science or big on ego - and deep in pocket.

But a new technique, described in the British journal Nature, has slashed the cost and time of genome sequencing, in an important step towards tailor-made medicine.

The human genome comprises around three billion base pairs – the 'rungs' in the ladder of the chemical code for life. The Human Genome Project (HGP), a consortium of public-sector scientists, spent 437 million dollars (about R3.4 billion) and 13 years to complete the first sequencing of the genome, in 2003.

It tied in a race against maverick biologist Craig Venter, who developed a fast-track sequencing method. Later, Venter's own genome was sequenced. That project, completed last September, cost around 100 million dollars (about R786m).

How it was done
The next-generation technique, led by the Rothberg Institute for Childhood Diseases Research in Connecticut, sequenced a sample given by James Watson, the Nobel laureate who co-discovered the DNA double helix.

It dispenses with the laborious and costly cloning of the sample by bacteria, which is the precursor to the traditional sequencing method. Instead, the sample is directly amplified by a process called polymerase chain reaction (PCR).

The long string of 'rungs' is then broken up and unravelled by parallel sequencers, and the data then fed into a powerful computer for reassembly and analysis.

Fast, low cost approach
In all, Watson's genome took less than a million dollars (about R8m) and a mere two months to produce, the study says. This fast, low-cost approach "is an important milestone in our ability to connect 'personalised genomes' to 'personalised medicine'," say its authors.

Biologists are working hard on deciphering the code, seeking to identify flawed genes that may pass on inherited disease or expose the individual to enhanced risk of cancer, smoking addiction, obesity or alcoholism, for instance.

In the future, they hope, an individual may get medicine that is tailor-made for his or her genome, to maximise the benefits and minimise the side-effects. – (Sapa)

April 2008

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