Saturday, February 03, 2007

Biery/Pomeroy in SMGF

Tomorrow's post, The last Berry, was going to run today until I decided to take one more look at SMGF and found this additional alternative spelling.    So here's the new haplotype.Using Whit Athey's Haplogroup Predictor this haplotype is haplogroup G2 with a fitness score of 81 and a probability of 100% (excluding DYS452 which doesn't fit the choices).

And here's Mr. Biery's pedigree -Recognize this person?    If so, we need to put him in touch with Michael, #69, who is a 28 marker PERFECT MATCH!

Take a look at the Genetic Distance Table -
Why do I say a 28 marker match when Michael has tested 37 markers and SMGF Biery has 39 markers?    Because of all those, only 28 of their markers tested are common to both.    Take a look at this haplotype table -
And finally, the TMRCA -
Even though I personally prefer to work with genetic distances to estimate 'relatedness' and don't find much use for the Time to Most Recent Common Ancestor table, some might, so I think I should take a minute to explain just what it tells us.

First, notice that at the bottom of each table we will find a note of the probability used for the estimation.    This can typically vary from 50% to 95%.    In this case we used 75%.    In addition, the subject of generation length is always the subject of great debate and the generation length chosen will obviously also affect the outcome.    That is also stated there.

So let's look at a specific example.    Since this is a posting about the SMGF Biery guy, let's look at SMGF Biery and Michael, #69.    Look where their respective lines on the horizontal and vertical axes intersect and you will see the number 150.    What this means is that there is a 75% probability that Michael's and SMGF Biery's common ancestor will be found within the past 150 years.    It doesn't tell us when within the past 150 years, though, and also necessarily includes the 25% possibility that he might be beyond the 150 years.    Here again, as in the other measurements, additional markers increase the precision of the test.

For further study see Time to Most Recent Common Ancestry (TMRCA) Calculator Using Genetic Marker Similarity Between Two Individuals, Bruce Walsh, Ph.D.


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