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This is a basic question that I should probably know the answer to, but don't. Could/would somebody that is pretty closely related to me via Y-DNA testing (GD=2 over 67 markers) also show up as a autosomal match under the Family Finder testing, matching on a chromosome(s) other than the Y-chromosome?
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Autosomal testing (such as Family Finder) is very good at detecting close relationships, out to about third cousins (although the rule of thumb is that about 10 percent of actual third cousins probably won't be detected as matches from autosomal DNA). Beyond third cousins, the percent of actual relatives that are not detected as matches goes way up -- around 50% for fourth cousins. So, yes, a Y-DNA match could show up also as an autosomal match, if the relationship is not too distant. However, Y-DNA usually mutates very slowly, so you would expect the Y chromosomes of third cousins related through common patrilineal descent, for example (they would share a common great-great-grandfather), to be nearly identical. -
First, the match would have to have done both tests. Most Y-DNA matches, even if they have done Family Finder, won't show up because the relationship is too distant. If you do find one who shows up on both, it's worth getting in touch and comparing trees, though I think about 9 out of 10 people these days don't have trees and couldn't care less.Comment
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Could? Definitely. Would? Not necessarily -- it depends on the factors that McCoy and Moberly mention in their posts.Comment
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