Re: Marker Difference meaning -3 men sharing descent of 250 years
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In reply to:
Marker Difference meaning -3 men sharing descent of 250 years
Nancy Stein 10/29/09
Nancy,
Nancy,
It is really the luck of the draw. Projects sometimes start out with runs of no mismatches or all mismatches. However, they eventually get near the expected number. Close cousins often mismatch more than very distance cousins, so that there is no way to predict exact relationships. All you can really say is that they either do or do not belong in the same family tree.
Since you have a paper trail, you can deduce the ancestral haplotype. It is much easier and more accurate to compare those of descendants to it than to one another, since many recent mutations will have been eliminated in the ancestral. We normally deduce the ancestral by testing descendants of 2 or more his sons until there are matches on all markers.
http://genforum.genealogy.com/dna/messages/1364.htmlhttp://genforum.genealogy.com/dna/messages/1364.html
I am assuming that the most recent common ancestor of A,B and C is the immigrant born 1741, but, if it was a son, grandson, etc., that person would be the progenitor in our analysis. The ancestor b. 1741 would likely have the same haplotype, however.
Note that we do not have descendants of enough sons tested to deduce the immigrant's haplotype by the usual method. However, we can use the results for either A or B to compare to C. We find that C matches either A or B on all markers, except 460. Thus, the ancestral would be DYS447=25, DYS570=17 and CDYb=40.
It seem likely from the paper trail that D is not descended from the MRCA of A, B and C, the immigrant born 1741 in MD.This suggests a more remote MRCA for all four who was DYS460=12. Thus, it is likely that MRCA(A,B,C) also had a 12. If an ancestor and a descendent have the same value on a marker, those in between will also have it.
In addition, since A and B have a 12 there, their MRCA would have it also. Thus, it is the more likely value.
Comparing A, B, and C to the likely ancestral haplotype ofDYS447=25, DYS460=12, DYS570=17 and CDYb=40 plus the other matching markers, we find:
A, 2 mismatches
B, 1 mismatch
C, 1 mismatch
34/37 or better to the immigrant's deduced haplotype is a good match in the usual genealogical time frame.33/37 and maybe 32/37 matches are in a gray area and suggest testing other branches or upgrading to 67 markers. However, with good paper trails it would be likely that they are good matches.
If the ancestral were 11 at DYS460, they would still all be within the 3 mismatches considered to be related.
Bob Stafford