Of Sequences and Spotted Turtles…   Leave a comment

All those Spotted turtle DNA samples we collected in the spring have now been processed in the Laboratory of Molecular Studies at the Royal Ontario Museum. This lab work was completed during the fall, and now it’s time to see what our results can tell us about Ontario’s Spotted turtle populations! The markers we use are called microsatellites, and here’s how it works:
“Microsatellites” are specific sections of DNA which don’t code for anything and contain repeating sections that are only a few nucleotides long. Nucleotides are the building blocks of DNA – the bits that make up the DNA sequence. DNA is made up of four different nucleotides called adenine, guanine, cytosine and thymine – abbreviated A, C, G and T. Because microsatellites contain these repeats, the DNA is not always accurately copied in these sections. Sometimes, a microsatellite which contains 6 repeats is miscopied so that the new DNA strand contains 5 or 7 repeats instead.
The reason this is useful information is that every turtle (or person) has 2 copies of each microsatellite, each of which may have a different number of repeats. These differently sized copies are called alleles. The alleles you (or a turtle) carry are inherited from your parents. For example, if your mother has an allele with 17 repeats and another allele with 10 repeats at a particular microsatellite, then you inherited either the copy with 17 repeats or the copy with 10 repeats. You also carry a copy of one of your father’s two alleles. Your kids will carry a copy of one of the two alleles you got from your parents, and so on.
You already know that the length of the alleles changes slowly over time as microsatellites are occasionally miscopied. This means that when two groups of turtles are separated, the genetic profiles of these different populations gradually start to drift apart as they begin to contain different alleles from one another. As a result, each population ends up with a unique genetic fingerprint or profile. This process can take many generations and turtle’s have very, very long generation times! However, our results are showing that the genetic profile of some Ontario Spotted turtle populations have already become significantly different from one another.
These results are exciting for several reasons. They will tell us about historic connections between populations because we can see which populations which are now fragmented and isolated from one another are the most similar. And they will allow us to take our next step and build an assignment test, which will allow us to assign confiscated, poached individuals back to their population of origin. This test is in the works… more to come soon!
– Christina Davy

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Posted January 24, 2012 by thinkingturtles in Uncategorized

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