Hi Ann Thank you for the image. Dad and I have tested and the longest segment we have in common is 267.21 cMs with almost 60,000 SNP's, so would it be wrong to guess that the longest segment is his surname ? The next longest is 206.75 cM's most likely a grandparent line? All other segments are under 200cMs., with less than 50,000SNP's There has been a lot of talk about IBD and IBS, with over 10 cMs being IBD. Is there a similiar finding with the number of SNP's where over a certain amount you would be related to the match for sure? Karen

Dear Karen, I would be cautious about assuming that a specific number of SNPs in a matching segment guarantees that the segment is IBD. I believe that a significant majority of matching segments that contain over 2000 SNPs are IBD. However, as I pointed out in a recent message at least one matching segment in my recent analysis that was apparently IBS contained 2400 SNPs. My personal view is that a majority of matching segments that contain 1000-2000 SNPs are IBD, but a portion are IBS. Significant caution is advised when evaluating segments where the number of SNPs are under 1000. As Ann Turner and others have pointed out previously you need to be careful about matching segments on chromosome 6 that are between about the 25 million and 35 million BP positions since many of these matching segments contain over 2000 SNPs, but most segments in this region are IBS. Here is some data from my recent analysis of my wife's and my Family Finder data when compared to our parents: # of SNPs %IBD %IBS >2000 95 (78/82) 5 1000-2000 76 (62/82) 24 500-1000 25 (4/16) 75 It should be noted that one of the four segments that was over 2000 that was IBS was on chromosome 6 between the 27 million and 34 million BP positions. Unfortunately the Ancestry Finder data that 23andMe provides doesn't include the number of SNPs in the matching segments. Sincerely, Tim Janzen -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Karen Hodges Sent: Thursday, January 12, 2012 1:32 PM To: [email protected] Subject: Re: [AUTOSOMAL-DNA] cM segments for close ancestors Hi Ann There has been a lot of talk about IBD and IBS, with over 10 cMs being IBD. Is there a similiar finding with the number of SNP's where over a certain amount you would be related to the match for sure? Karen

Hi Tim Thanks for sharing your findings on your own family's SNPs. Karen > > # of SNPs %IBD %IBS > >2000 95 (78/82) 5 > 1000-2000 76 (62/82) 24 > 500-1000 25 (4/16) 75 > > > >