Saturday, February 13, 2010

another old bloke with a genome sequence

I was intrigued to find out from the article featured on the cover of Nature this week that the ninth man to have his complete genome sequence published (we’re still waiting for the first woman) has been dead for some 4,000 years. A lock of hair conserved in permafrost in a Greenland location inhabited by the Saqqaq culture had kept the DNA well enough to do a proper sequencing (20fold coverage) of most of his genome.

To be fair to the researchers, they didn’t know they were looking at a male genome until they read out the results, so it isn’t their fault if we get another old bloke. What’s also interesting is that this work appears to have been inspired by the sequencing of the woolly mammoth genome a couple of years ago, which demonstrated that frozen hairs are a good source of relatively pure DNA for sequencing. By contrast, Egyption tombs would yield more samples, but the DNA would be less well preserved and more likely to be contaminated with DNA of other species and indeed of modern humans.

Studying the SNPs (one-letter variations) of the individual in comparison with the spread of SNPs today, the researchers found he was most closely related to people living in Siberia today, pointing to an additional migration event that hadn’t been on record before. They also obtained genetic clues to his looks, from his hair and skin through to the shape of his teeth, hence the fairly detailed portrait that graces the cover.

As genome sequencing is likely to become a lot cheaper and faster still, we can look forward to other ancient genomes from frozen or indeed museum specimens (eg the genome of Tycho Brahe might cast an interesting light on Danish history and the rotten affairs that possibly inspired Shakespeare to write Hamlet). The ethical side of sequencing long-dead people will be tricky though, especially if there may be an impact on our understanding of their biographies.


Reference:
Morten Rasmussen et al.
Ancient human genome sequence of an extinct Palaeo-Eskimo
Nature 463, 757-762 (11 February 2010) | doi:10.1038/nature08835;
full text (appears to be open access)

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