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Alaska Ecosystems

Real-Time Polymerase Chain Reaction Analysis of Northern Fur Seal Telomeres

Bobette Dickerson with the Alaska Ecosystems Program traveled to Juneau, Alaska, to use the quantitative PCR (polymerase chain reaction) machine in the genetics facilities at Auke Bay Laboratories to examine an alternative approach to ageing northern fur seals.

Currently, the only reliable way to age northern fur seals is to examine the "rings" in their teeth, which, of course, requires the removal of a tooth. For obvious reasons, this is a less than desirable method for ageing. Recent studies (primarily focused on birds) have examined the relationship between the length of an animal's telomeres and the age of the animal, which has led to the ability to estimate age in some species based on a small genetics sample.

Every chromosome has a telomere attached to the end of it (tandem repeat sequence) which, in general, shortens as the organism ages. However, the telomeres of a given individual can and will shorten faster or slower than the telomeres of others based on factors besides age, such as environmental perturbations and other stressors, and the effects of these factors and ageing on the shortening of telomeres vary by species. Thus, the feasibility of using telomere length as an indicator of age must be validated for each species, and possibly each population, in which it is attempted.

Because telomeres exist on each chromosome in a given organism and do not shorten at exactly the same rate on each chromosome, it is difficult to determine the average length of the telomeres in a given animal using traditional molecular techniques. The quantitative PCR machine allows for an analysis of real-time PCR (RT PCR).

By comparing the results of the RT PCR conducted on telomeres with results for a single copy gene in the same animal, Bobette was able to estimate the relative average length of the telomeres in 200 northern fur seals (collected from the Pribilof Islands) for whom age will be known based on examination of their teeth. It is hoped this will result in a reliable age-to-telomere-length curve, which would enable us to age animals with just a small tissue or blood sample.

Although the results are pending, thus far, we know that the RT PCRs worked very successfully, and we will know by this fall if this method is sufficient for ageing northern fur seals. Without the support and collaboration of the ABL research team, this work would not have been possible.

By Bobette Dickerson

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