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Fergus(s)on DNA ProjectVirginia: William Ferguson and Judah WoodTMRCA Analysis |
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The numbers in red show how many generations removed each participant is from the family's most recent common ancestor. One of the difficulties in the computations to follow is comparing participants who are not of the same generation. Ignoring the difference and using a Family TMRCA based on the most distant tested generation is a reasonable approximation. It is equivalent to assuming that the haplotypes of persons whose generation does match the Family TMRCA are unchanged for the difference in generations being ignored. The approximation is reasonable because the probability of a haplotype changing from father to son is known to be low. Compared with other choices one might make, the choice of a most distant generation results in the largest Family TMRCA and presents a more severe test when compared with the 95% TMRCA. Finally, the numbers in blue are the resultant TMRCA.
The tables below compare the actual pairwise TMRCA as deduced from the above diagram with theoretical computations of the 5% and 95% TMRCA.
| Time to Most Recent Common Ancestor (Generations) | |||||||||
| Actual TMRCA | M i c h a e l |
T o n y |
J o h n |
J a m e s |
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| Michael_Ferguson | 67 | 7 | 7 | 4 | |||||
| Tony_Lee_Ferguson | 7 | 67 | 7 | 7 | |||||
| John_Wesley_Ferguson | 7 | 7 | 67 | 7 | |||||
| James_Auther_Ferguson | 4 | 7 | 7 | 37 | |||||
| 95% TMRCA | |||||||||
| Michael_Ferguson | 67 | 12 | 21 | 14 | |||||
| James_Auther_Ferguson | 12 | 67 | 24 | 18 | |||||
| John_Wesley_Ferguson | 21 | 24 | 67 | 18 | |||||
| Tony_Lee_Ferguson | 14 | 18 | 18 | 67 | |||||
| James_Auther_Ferguson | 14 | 22 | 27 | 37 | |||||
| 5% TMRCA | |||||||||
| Michael_Ferguson | 67 | 1 | 4 | 2 | |||||
| James_Auther_Ferguson | 1 | 67 | 6 | 3 | |||||
| John_Wesley_Ferguson | 4 | 6 | 67 | 3 | |||||
| Tony_Lee_Ferguson | 2 | 3 | 3 | 67 | |||||
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| - Infinite allele mutation model is used
- Average mutation rate varies: 0.0033 to 0.0049 - Mutation rates from Chandler, Little & Hutchison - Values on the diagonal indicate number of markers tested - Probability is 95% that the TMRCA is no longer than indicated |
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In these cases all the actual TMRCA are greater than the 5% numbers and less than the 95% numbers as they probably should be. It is concluded the resultant set of pairwise actual TMRCA defined by the genealogical structure is consistent with the corresponding set of pairwise TMRCA computed from the DNA mismatches.
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