BTW, this wikipedia page has a nice summary of Y-STRs...
http://en.wikipedia.org/wiki/List_of_Y-STR_markers
-Michael
> I know that most eyes looking at the emails from this list probably glaze
> over when the subject of genetics comes up. For those interested, here's
> an explanation of a couple of terms that might help.
>
> SNP, which stands for Single Nucleotide Polymorphism:
>
> The "alphabet soup" of DNA is comprised of those chemicals that abbreviate
> to A, G, C and T. They're called nucleotides. There are more nucleotides
> but only those four make up the molecules of DNA. Occasionally a SNP will
> mutate from one of those four letters to another. For example, the SNP
> we've talked so much about, L448, nicknamed "Young Scandinavian," is the
> result of a C becoming a T--a simple chemical conversion. This is believed
> to have happened with an individual in Norway about 2300 years ago. SNPs
> tend to be highly stable. Once a mutation occurs, it is passed down
> unchanged for hundreds or thousands of generations. I had about 1700 SNPs
> sequenced at 23andMe. Don had very many more sequenced at NatGeo.
>
> STR, which stands for short tandem repeat:
>
> This is a different animal. The results we see at
> http://www.familytreedna.com/public/Cooley/default.aspx?section=yresults
> are STRs. They represent a string of nucleotides (A, T, C and G) that
> repeat a certain number of times. For example, DYS393--the first column
> from our results page, has the sequence AGAT repeated X number of times.
> In our case, it's repeated 13 times. Someone who has 15 repeats at that
> location, as is the case with the testers in group CF12, are said to be a
> genetic distance of two from us at that position. Unlike SNPs, STRs are
> volatile and regularly add or delete a sequence or more with some
> regularity.
>
> The stability of SNPs, then, are great for "deep ancestry," the sort of
> thing that population geneticists are interested in. STRs, on the other
> hand, are great for genealogy because the nature of their volatility means
> that comparisons can be made within about 15 generations, instead of
> millenia. In other words, two patrilineages from the same individual 20
> generations ago, say about 650 years, are not expected to be easily
> matched--too many STR mutations would have occurred along each line.
>
> Feel free to ask questions.
>
> -Michael
>
--
Second VP, the Cooley Family Association of America
Administrator, the Akins DNA Project
Administrator, the Ashenhurst DNA Project
Administrator, the Bishop DNA Project
Administrator, the Eldridge DNA Project
Administrator, the alt-McDowell DNA Project
Co-Administrator, the Cooley DNA Project
Co-Administrator, the McDougall DNA Project
Instructor "Genealogy and Family History," the Osher Lifelong Learning
Institute (OLLI)
B.A. Humboldt State University, History
Received on Sun Nov 03 2013 - 23:28:12 MST