DNA Damage on the Waterfront

Herring gulls nesting in a polluted Canadian harbor have a higher rate of genetic mutation than do gulls in the countryside. The finding suggests that harbor pollutants may damage DNA, but so far, no ill effects from this damage have been established.

Behavioral ecologist James Quinn of McMaster University in Hamilton, Ontario, and grad student Carole Yauk tracked the mutation rate in junk DNA--regions that rarely code for useful proteins--in 35 families of herring gulls in Hamilton Harbor and 108 families in three less-polluted rural areas. Using DNA fingerprinting, the researchers found that the mutation rate was as much as eight times higher in harbor gulls than in country birds.

"The mutant fragments stick out like a sore thumb," Quinn says. Because herring gulls don't migrate, he and Yauk concluded that some local factor is responsible for the varying mutation rates. The top suspects, Quinn says, are polyaromatic compounds such as benzo[a]pyrene. Their findings appear in the 29 October Proceedings of the National Academy of Sciences.

The results are "extremely interesting," says Alec Jeffreys, a DNA fingerprinting expert at the University of Leicester, England, who has found a similarly elevated junk DNA mutation rate in Belarussians exposed to radioactive contamination from Chernobyl. However, mutations in junk DNA crop up far more often than do mutations in regions of vital DNA. "I'd be very loath to extrapolate what this means for the rest of the genome," says Jeffreys. Quinn agrees, particularly since the harbor gulls appear healthy.

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