The researchers also discovered previously unrecognized genes that are evolving rapidly. These genes are attractive candidates for further research into which genes may be interacting with the human immune system.

"We also found that within classes of antigens, some are under much stronger selection than others, which people hadn't found before," he said. "We are able to make hypotheses about which ones are actually interacting with the immune system and which ones are not, based on this new finding."

Fraser emphasized that the technique, referred to as codon volatility, complements comparative gene methods common now. Codon volatility can tell about recent evolutionary pressure on genes, while comparative methods can tell about evolutionary pressure over millions of years.

The codon volatility method has limitations, however, he said. It relies on the fact that the proportion of each of the four DNA nucleotides is fairly uniform across the entire genome of an organism. In humans, however, the proportion is different at different places in the genome. Nevertheless, Fraser said the group is at work modifying the method to analyze codon volatility in the human genome.

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Contact: Robert Sanders
rls@pa.urel.berkeley.edu
510-643-6998
University of California - Berkeley
29-Apr-2004