Monday, 27 November 2006

How many Y-DNA markers to test

At the meeting of the BIFHSGO DNA group last Saturday we had ten people, a mix of folks who had experience with a test and those considering it. For the latter the biggest question was how many markers to test. Who wouldn't ask when you are looking at the difference between $US 99.95, plus $US 7.55 shipping and handling and tax, for a 12 marker test through the Genographic Project, and $US 349 for a 67 marker test through Family Tree DNA?

There are good reasons to start with a 12 marker test. If your deep roots, for times before the adoption of surnames, are of most interest then a 12 marker test is all you need. Two recent books on DNA in Britain, by Sykes and Oppenheimer, are based on 12 or fewer markers. By testing through the Genographic Project you will get a clear explanation of your results, and contribute to a worthwhile anthropological project.

You also have the opportunity to add your data to the large Family Tree DNA database and order additional tests without having to take another sample. The large database is important as the chances of finding a genetic cousins are better. According to the FTDNA web site, if you match exactly on 12 markers with someone with the same or variant surname then there is a 99% chance you have a common ancestor within the period in which surnames have been used. Finding that match might motivate you to upgrade. That is just what happened with a man in Australia with the same surname as me. He tested through the Geneographic Project, transferred his information to the FTDNA database. When we found a 12 marker match he decided to upgrade to a 37 marker text.

For anyone with an interest in DNA, whether for anthropology or general genealogical interest, a Genographic Project kit would make a great Christmas gift.

However, if you are looking to establish, or to disprove, a specific relationship within the period of surnames you need to test a larger number of markers. The closer the match on a greater number of markers the more certain you can be of a recent common ancestor. The less alike the DNA the more unlikely there is to be a common ancestor.

A final word; there are other respected commercial testing companies besides FTDNA. Some analyse more markers at less cost than FTDNA. However, none of them have as large a database as FTDNA. That's important if you're looking to discover genetic cousins.