Scientists decode half of the Neanderthal genome

December 10th, 2008 - 2:29 pm ICT by ANI  

London, Dec 10 (ANI): Scientists have decoded half of the Neanderthal genome and are aiming to sequence the rest by the years end.

According to a report in New Scientist, researchers will roll out a rough draft of the Neanderthal nuclear genome after their sequencers have read every letter in the genome on average once.

However, the fragmentary state of the DNA sample, from bones recovered in Czech Republic, means that the first draft will offer only a tantalizing glimpse of the genome to researchers who hope to better understand Neanderthal biology and human evolution.

Some 38,000 years of decay has left the DNA in tatters and strewn with contamination from bacteria and human handlers.

Its not like sequencing any other genome, said Adrian Briggs, a researcher at Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who is involved in the project, along with colleagues Edward Green and Svante Paabo.

When the same team sequenced the far shorter mitochondrial genome, they decoded each letter an average of 35 times from different samples, which was enough to ferret out contamination and changes that happen as DNA strands crumble over the years.

It will take another year or two for the complete Neanderthal nuclear genome sequence to reach a comparable level of quality, according to Briggs.

In the meantime, he and his colleagues will make thrifty use of the rough draft to understand Neanderthal biology, evolution and their relationship to humans - and the big question: did they interbreed or not?

The rough draft is also expected to say some things about Neanderthal biology.

Were starting to be able to answer individual questions about concrete genes, said Briggs.

Preliminary results suggest that Neanderthals were lactose intolerant, hardly surprising since the ability to digest dairy products in adulthood only became common in humans after the domestication of cows, 10,000 years ago.

Neanderthals also seem to lack a mutation associated with increased fertility, identified in Icelanders. A 2005 paper suggested that this mutation had entered humans through inbreeding with Neanderthals.

Nor do Neanderthals boast mutations in a gene called microcephalin, linked to bulging brains in humans.

This might shoot down another controversial hypothesis contending that this version of microcephalin also evolved in Neanderthals, and then spread to humans through inbreeding.

With a draft sequence, Briggs and his team will be able to home in on more genes known to have changed since humans split with chimpanzees, six million years ago, and determine where Neanderthals stand in relation.

This will shed light on the evolution of modern humans after their ancestors split from Neanderthals, more than 600,000 years ago. (ANI)

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