Gene regulation, not just genes, is what sets hu...(f sperm but the coding regions of neural...)

Date:8/13/2007

f sperm, but the coding regions of neural-related genes had shown very little sign of positive selection in these studies. Yet, as far back as 1975 when Mary-Claire King and Allan Wilson first said humans and chimps were 99 percent the same genetically, they had offered the suggestion that greater differences might be found in the regulatory regions.

The type of analysis performed by the Duke team couldnt be done until the macaque genome was published in 2005 because they needed a third, closely related relative to compare the regulatory sequences.

The mouse genome had been used as a reference point for comparing the coding sequences of humans and chimps, but the non-coding sequences have generally evolved much faster. Mice wouldnt work for analyzing the non-coding sequences, because theyre too different from humans and chimps, Haygood said.

While the biochemistry that cells use to turn food into energy is essentially the same across most animal species, the fine-tuning of how an organism deals with the different sorts of sugars and complex carbohydrates in its diet lies in the regulatory sequences, Wray said.

Chimps are fruit-eaters, for the most part, and would not last long away from their fruit-rich forest. The sugars in their diet are relatively simple to break down and convert to cellular fuel. Humans, on the other hand, eat a wider array of foods, including many the chimps would simply not be able to digest like starchy root crops. The researchers found dramatic differences in the regulatory regions of their genes for breaking down more complex carbohydrates. It may be that parts of the human metabolism are cranked up to digest carbs down to simpler sugars.

Regulatory changes have adapted to changing circumstances without changing the essential chemistry of metabolism, Wray said. This may set the stage for a more focused analysis of the human diet.

Much is being written and hypothesized about how dietary
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Contact: Karl Leif Bates karl.bates@duke.edu 919-681-8054 Duke University Source:Eurekalert

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