Friday, 8 April 2011

... 12, 25, 37, 67 ...

What is the significance of the sequence  .. 12, 25, 37, 67 ... ? What number comes next?

If your answer to the first question was the number of Y-chromosome STR markers Family Tree DNA have, or have had, tests for count yourself a DNA savvy genealogist.

If you answered 111 to the second question count yourself as really up to date.

Family Tree DNA are now offering an upgrade from 67 to a 111 Y-chromosome marker test "intended for those who wish to refine the time to most recent common ancestor (TMRCA) calculation with a close or exact match and who wish to improve the confidence in a match."

In the FAQ section of the company website FTDNA give advice on the desirability of upgrades, including this table copied from FTDNA with permission with information on Time to Most Recent Common Ancestor (MRCA).

With my best match 65 out of 67 markers, there's a 95% probability that the common ancestor is within 14 generations. Upgrading to 111 markers, and if there were a perfect match for all the new markers, that 95% confidence would be reduced to 9 generations. That's still three generations shy of my earliest documented ancestor.

The new markers seem to be of less interest to genealogists than surname study researchers looking for genetic clusters which will help refine segmentation into groups.

Considering an upgrade? I suggest reading the FTDNA FAQ at http://goo.gl/BTo2p and keep in mind their advice "Test only what you need, and upgrade only when necessary"

By the way, early versions of the Family Tree DNA website refer to an 11 marker Y-DNA test, which was soon changed to 12 markers, and the table above shows values for 10 markers, which is why I hedged bets a bit with the sequence by starting with ....

1 comment:

Leaves of Heritage Genealogy said...

I thought these were my measurements! LOL =0) Thanks for the info.

Angela-