Surname DNA project
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In most cultures, there are few or no matrilineal surnames, or matrinames, so there are still few or no matrilineal surname projects. However, DNA tests are equally important for the two sexes (see genealogical DNA test).
Because surnames are passed down from father to son in many cultures (patrilineal), and Y-chromosomes (Y-DNA) are passed from father to son with a predictable rate of mutation, people with the same surname can use genealogical DNA testing to determine if they share a common ancestor within recent history.
When two males share a surname, a test of their Y-chromosome markers will determine either that they are not related, or that they are related. If they are related, the number of markers tested and the number of matches at those markers determines the range of generations until their most recent common ancestor (MRCA). If the two tests match on 37 markers, there is a 90% probability that the MRCA was less than five generations ago and a 95% probability that the MRCA was less than eight generations ago.
A Y-DNA test ranges from 10 to 111 markers on the Y chromosome. Most surname projects suggest at least 25 markers. Test results tell how many repeats a given subject has at a particular marker; the variations of repeats are known as alleles. For example, at DYS455, the results will normally show 8, 9, 10, 11, or 12 repeats. The specific test results for a given individual are referred to as a haplotype. When a surname project has enough participants' test results, it can group similar test results together and determine a modal haplotype for each such group of similar test results.
Surname projects are now being hosted by testing companies. Some labs even store the submitted samples for a number of years, enabling additional tests to be performed as they become available. By far the largest collection of Y-DNA test results is maintained by Family Tree DNA, including many surname projects that make direct use of those results.
The Y chromosome has been studied intensely and variations have been divided into Human Y-chromosome DNA haplogroups, based upon the results of the number of alleles in certain positions called markers. These "markers" have been chosen for their demonstrated ability to predict the haplogroup of the tested individual. Each testing company used a different set, although many are overlapping. This had allowed Y-STR database websites such as Ybase and Ysearch (both now defunct) to convert scores from several companies and find matches within their database for submitted results.
- Sykes, Bryan (2001). The Seven Daughters of Eve. W. W. Norton. pp. 291–92. ISBN 0-393-02018-5.
Sykes discusses the difficulty in genealogically tracing a maternal lineage, due to the lack of matrilineal surnames (or matrinames)
- "Interpreting Genetic Distance Within Surname Projects". FamilyTreeDNA. Archived from the original on 6 February 2012. Retrieved 13 December 2011.
- "Marker details for DYS455". Y-Chromosome Marker Details (Y-STR database). Sorenson Molecular Genealogy Foundation. Retrieved 14 January 2012.
- Pomery, Chris (January–March 2010). "Finding Out What We're About: Changes in the field of DNA testing" (PDF). Journal of One-Name Studies: 20–21. Retrieved July 10, 2013.
- Carpenter, John R. (dated May 17, 2017). "DNA Testing – What you need to know first" (PDF). Retrieved August 5, 2019.