A molecular 鈥渢imer鈥� implicated in ageing also has a profound effect on year-to-year survival in relatively young animals. If the same holds true in people, a simple genetic test may some day offer a peek at a person鈥檚 life expectancy.
Mark Haussmann and his colleagues at Iowa State University in Ames took blood samples from 22 one-year-old tree swallows near Ithaca, New York. For each bird, they measured the length of the repeated DNA sequences known as telomeres that cap the ends of chromosomes. Because telomeres shorten every time a cell divides, they set an upper limit on the number of divisions that can happen, and thus could play a big role in ageing.
The researchers also recorded each bird鈥檚 fate. Of the 11 birds with the longest telomeres, 10 returned after their first winter migration, while only four of the 11 with the shortest telomeres made it back (Biology Letters, DOI: 10.1098/rsbl.2005.0301). Female tree swallows almost always return to the same nesting sites each year, so those that failed to come back had probably died.
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Previous work has shown that 60-year-old people and elderly worms with longer telomeres can expect to outlive those with shorter telomeres. But Haussmann鈥檚 study is the first to show that telomere length is important in young animals.
