Chris IBD means it's from an ancestor; IBS means it could have been contributed by a variety of ancestors, and it's just in the DNA "soup". But the segments don't come with tags indicating which they are, so you don't know if a segment is IBD or IBS. Some folks deal only with segments over 10-12cM or so to pretty much guarantee they are IBD and come from a specific ancestor. FTDNA uses 7.7cM as the cutoff, and won't report a match to you with anyone less than that. All of your FF matches have at least one segment that is 7.7 or larger. All of your FF matches also have some other segments, which are smaller. It is those smaller segment that are often IBS, and not helpful. However some may be IBD and represent a tie to a Common Ancestor - you just don't know until you check (some folks keep all segments over 5.0cM in their analysis). You should be looking for a Common Ancestor with each of your matches. Those with deep ancestries may find multiple Common Ancestors - in this case one could be on one segment and the other could be on a smaller segment. IMO, the important thing is to determine Commin Ancestors with each atDNA match. I am currently only using the segments above the cutoff (7.7cM for FF), but plan to go back later and test the segment map against all the reported segments and draw my own conclusions about what percentage of the smaller segments are IBD. Jim - Sent from my iPhone - FaceTime! On Jun 21, 2012, at 8:16 AM, Christina Hunt <[email protected]> wrote: > Thanks Tim, > I was advised to do this kind of mapping and have also started doing the mapping. > It is rather slow going :) > Thanks for explaining IBD and IBS. I thought they were illnesses when I first > saw that. Still didn't know what the initials stood for. > I have drop box. Had not thought of putting my DNA info in there. Good suggestion. > > I appreciate it. > Chris

Dear Chris and Jim, As a general rule for segments between 5 and 10 cMs in length if both a parent and a child both have an HIR on the same segment that they share with a match match at 23andMe or Family Finder, then that particular segment is IBD. If the parent matches someone else, but the child doesn't match that person then you can't be certain whether or not the segment is IBD or IBS without more information. The more children that are tested in situations like this, the higher the chance you will be able to determine if a segment if IBD or not. If you test 2 children and one parent then you should be able to identify 75% of all IBD segments. If you test 3 children and one parent then you should be able to identify 87.5% of all IBD segments. If you test 4 children and one parent then you should be able to identify 93.75% of all IBD segments. This is one of the main reasons I plan to do autosomal tests on my two brothers in the near future even though I have already tested my parents. Sincerely, Tim Janzen -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jim Bartlett Sent: Thursday, June 21, 2012 5:46 AM To: [email protected] Subject: Re: [AUTOSOMAL-DNA] Chromosome Browser Chris IBD means it's from an ancestor; IBS means it could have been contributed by a variety of ancestors, and it's just in the DNA "soup". But the segments don't come with tags indicating which they are, so you don't know if a segment is IBD or IBS. Some folks deal only with segments over 10-12cM or so to pretty much guarantee they are IBD and come from a specific ancestor. Jim