HATCHER website: http://hatcherfamilyassn.com HALL DNA project: http://homepages.rootsweb.com/~nhatcher/hall/HDNAtest.htm "If you can't stand the skeletons, stay out of the closet" - Val D Greenwood Looks like I stand corrected and that makes me a very happy camper! Below you will find the question I asked of Dr Barry Hall, a geneticist, and below that you can read his response. No, we do not have an impossible situation but, yes, it's rare. So you know who we're talking about - A1 is Amy; A2 is Josh; B1 is Chuck. ------------------------ HATCHER website: http://hatcherfamilyassn.com HALL DNA project: http://homepages.rootsweb.com/~nhatcher/hall/HDNAtest.htm "If you can't stand the skeletons, stay out of the closet" - Val D Greenwood Thanks, Barry. May take me a day or two to get it online but will let you know when it's done. But I'm wondering if you could answer a quick (I hope) question for me. I have 3 Hatcher testers that all descend from the same man about 8-9 gens back thru 2 sons. Two testers (call them A1 and A2) have a common ancestor, their ggfather, who descends from son A. The 3rd tester is thru son B. At DYS-391 A1 = 11 (this is the value common to all the other 50+ testers in this family) A2 = 10 (and I considered this a mutation occurring between the tester and his ggfather). B1 = 10. One big "Say what?" I don't know what the odds are but I didn't think a mutation could occur in 2 branches of the same line at the exact same marker with the exact same value. We have excellent documentation on these 3 guys and I'm not seeing any "hole" where we could have made this kind of mistake since it appears B1 should be very closely related to A2 within the past 2 gens. None of these 3 have ever met the others nor have they ever lived remotely close to each other. Am I dead wrong in my thinking that there's something seriously wrong here? Is it really possible to have this identical mutation occur with testers who are related but not that closely related? Cheers, Nel ------------------------- (Response from Barry) When two individuals share the same allele (value at a particular marker) there are only two possibilities: (1) the alleles are identical by descent, meaning that they inherited that allele from a common ancestor. (2) the two alleles arose independently. Keep in mind that a mutation changes an allele from some state to another state; i.e. from 11 to 10, or from 10 to 11. Let's call the common ancestor of all three X, and the son who is the ggfather of A1 and A2 Y, and consider the two possibilities: (1) X carried the 10 allele. That means that a mutation from 11 to 10 occurred either in him or in an immediate ancestor who left no other descendants that are currently in the Hatcher DNA results. Somewhere between Y and A1 another mutation changed the 10 allele back to 11. That means that A2 and B share the 10 allele by descent from X. In total, two mutations occurred. (2) X carried the common 11 allele. In that case the mutation from 11 to 10 occurred twice, once somewhere between Y and A2 and again somewhere between X and B1. In total, two mutations occurred. We usually proceed on the assumption that the most likely explanation is the one that requires the fewest mutations. In this case that helps not one bit. First, it certainly is possible for the same mutation to occur multiple times in different branches, it is just a rare (unlikely) event. It is just as unlikely for the two mutations to be 11 to 10 and back to 11 as it is for two independent mutations from 11 to 10 to occur. Assuming that the DNA analysis is good in all three cases, we must conclude that an unlikely pair of mutations have occurred. We just don't know which scenario actually occurred. Keep in mind that the values 10 and 11 are the number of repeats of some sequence at locus 391. The most common mutation is a gain or loss of one repeat. Thus neither of the two possibilities is all that surprising. If the change had been 11 to 9, I would have been much more suspicious of your genealogy. Bottom line: I see no reason to think there is a conflict between the genealogy and the DNA results. The history simply include an improbable event. Barry