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Sunday, November 26, 2006

So, who molested the monkey?

Someone in the Bush family, I think one of the liberal regulars would do well to retort. But the news earlier this week had me laughing to myself, although unfortunately it's not actually as funny as my faulty memory would have had it:

Nearly six years after the sequence of the human genome was sketched out, one might assume that researchers had worked out what all that DNA means. But a new investigation has left them wondering just how similar one person's genome is to another's. Geneticists have generally assumed that your string of DNA 'letters' is 99.9% identical to that of your neighbour's, with differences in the odd individual letter. These differences make each person genetically unique — influencing everything from appearance and personality to susceptibility to disease.

But hold on, say the authors of a new study published in Nature. They have identified surprisingly large chunks of the genome that can differ dramatically from one person to the next.... According to the team's back-of-the-envelope calculations, one person's DNA is probably 99.5% similar to their neighbour's. Or a bit less. "I've tried to do the calculation and it's very complicated," says Hurles. "It all depends on how you do the accounting."

The answer is also unclear because researchers think that there are many more variable blocks of sequence that are 10,000 or 1,000 letters long and were excluded from the current study. Because of limits with their methods, the new map mainly identified variable chunks larger than 50,000 letters long.

This struck me as really funny, since last year people were going on and on about how we were something like 99.8 percent similar to chimpanzees. So, this news that humans spanned a range of at least .5 percent variance naturally had me wondering exactly who, besides Patrick Ewing, Gerard Depardieu and George W. Bush, was more closely related to chimpanzees than a perfect specimen of humanity such as Daniela Pestova.

Unfortunately, the 99 percent was always an exaggeration, as the following quote demonstrates.

Aug. 31, 2005 - The first comprehensive comparison of the genetic blueprints of humans and chimpanzees shows our closest living relatives share perfect identity with 96 percent of our DNA sequence, an international research consortium reported today.... The consortium found that the chimp and human genomes are very similar and encode very similar proteins. The DNA sequence that can be directly compared between the two genomes is almost 99 percent identical. When DNA insertions and deletions are taken into account, humans and chimps still share 96 percent of their sequence.

Still, if our intraspecies variation is significantly greater than previously thought, one presumes that this new discovery would also tend to separate us further from the chimps and sea urchins, barring Jenna pestering the primates at the zoo, of course. Renee or someone else versed in current biology textbooks will correct me if my assumption is incorrect, I'm sure.

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