Y-STR Conversions

The results of a Y-DNA test are either a string of plusses and minuses, or a series of numbers. The plusses and minuses are the result of a SNP (single-nucleotide polymorphism) test and denote the testee’s Haplogroup, while the string of numbers are the result of a STR (short tandem repeat) test and denote the testee’s haplotype.

To learn more one’s haplotype, or to compare it to other’s results, most people enter those results into a database such as Ysearch, Ybase, SMGF, YHRD, or the Y-STR Database. To do this, however, it is sometimes necessary to ‘normalize’ the numbers. For instance, one testing company might find a result of 27 for DYS481 while another finds a result of 23 on the same individual. This is typically due to different sequencing primers used by each company to characterize each particular STR.

Thanks to a post on the DNA-NEWBIE mailing list (if you are interested in genetic genealogy and not yet a member of this mailing list, you can sign up here), I learned of a spreadsheet that contains conversion numbers for many of the genetic genealogy testing companies:

“For you to be able to derive meaning from your results, you need to compare them to others’ results. Jim Pearsall, a genetic genealogist who has been tested by several DNA companies…compiled the following table of adjustments based on the reports provided to him by the companies.”

You can use this chart to convert the markers from one company into the nomenclature of a second company. There is more information about STR conversions at Ysearch and at Ybase.

HT: Justin Ryan posted the link to Mr. Pearsall’s conversion document to the DNA-NEWBIE mailing list.