Interviewee: Michael Hammer. Evolutionary geneticist Michael Hammer speaks about the markers used to analyze DNA variation in the Y chromosome. (DNAi Location: Applications > Human origins > Gene genealogy >The Y chromosome > The Y chromosome and ancestry)

There are two classes of markers that we use on the Y chromosome that have wonderfully complimentary properties, we have SNPs, single nucleotide polymorphisms that represent a change at a single base position. The mutation rate is very low, something on the order of 1 in 10 to the 9th per base per year. Or you want to, you could change that to 1 to 2, per 10 to the 8th, per generation or something, but in general they happen at a very slow rate. If you find a SNP it's unlikely that that same site is mutated twice. They tell us about deep history, going back 100,000 years, going back 20,000 years. There are another class of markers called microsatellites or short tandem repeats sometimes abbreviated STRs; we call them YSTRs when they're on the Y chromosome. There are a number of those kinds of markers, they have a high mutation rate, about four or five orders of magnitude faster mutation rate. So if we study those kinds of markers, in combination with SNPs, the slowly mutating markers, we can ask questions about different scales, different time scales in history, so we can ask questions about early origins of populations using SNPs, we can ask questions about recent migratory processes using STRs.

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