Chimp And Human DNA Comparison

October 17, 2006

Scientists look to the chimpanzee genome to better understand what

is uniquely human about our own. One goal is to find DNA elements

that show evidence of rapid evolution in the human lineage. In a new

study, published online in the open-access journal PLoS Genetics,

Pollard, at the UC Genome Center, and colleagues at

UC Santa Cruz led by Haussler used comparative genomics to

investigate the properties of a set of 202 carefully

screened " highly accelerated regions " (HARs).

The authors searched for stretches of DNA that were highly conserved

between chimpanzees, mice, and rats, comparing those sequences to

the human genome sequence in order to unravel the evolutionary

forces at work behind the human genome's fastest evolving regions.

Pollard explains that " most of the differences between chimps and

humans are not in our proteins, but in how we use them. " Only three

HARs lie in genes that are likely to encode proteins. The rest do

not appear to code for genes at all; instead, many HARs are located

close to genes involved in growth and development. The most

dramatically accelerated region, HAR1, appears to make a piece of

RNA that may have a function in brain development.

" They're not in genes, but they're near genes that do some very

important stuff, " Pollard said. Typically, non-coding regions of DNA

evolve more rapidly than regions carrying genes because there is no

selective pressure to stop mutations from accumulating. However, the

human-accelerated regions are highly conserved across the other

groups of animals that the researchers examined, suggesting that

they have important functions that stop them from varying too much.

###

This study was funded by the National Institutes of Health and the

Medical Institute.

Recommended Posts