Hi Jim That I understand. Its the under 7cMs matches that match only me on a Chromosome. I guess these are best put aside if there is no genealogy connection. Or two other matches come up in the same area for comparison to determine IBD or IBS. Karen On Sun, Oct 20, 2013 at 12:17 AM, Jim Bartlett <jim4bartletts@verizon.net>wrote: > Karen > > False positives from FF ICW can be determined by asking the two Matches in > question if they match each other on the same segment you match them. > Either one can confirm it. > > Also you can easily compare them at GEDmatch to see if and how much and > where they share (if they'll upload to GEDmatch). > > Also you can confirm them, one at a time, if they match a close cousin > (your close cousin can confirm the segment if you don't manage their kit). > > I would never think about comparing raw data. If they won't cooperate at > all (as above), they surely won't give you their raw data, either. > > Jim - Sent from my iPhone - FaceTime! > > On Oct 19, 2013, at 7:52 AM, Karen Hodges <rowantreek@gmail.com> wrote: > > > Hi Jim > > > > Thanks for your comments. I think I am good with the true matches now but > > the false positives can these only be determined by comparing the raw DNA > > when no genealogy match is found and is there a program that can do this? > > > > Karen > > > > > > On Sat, Oct 19, 2013 at 10:12 PM, Jim Bartlett < > jim4bartletts@verizon.net>wrote: > > > >> Karen > >> > >> In general I agree with Tim. I would add that Triangulation has a very > >> specific requirement: A=B=C=A. That is each pair (AB,AC,BC) must have a > >> shared segment (usually at least 7cM, but perhaps smaller with some > risk of > >> a false positive); AND each of these shared segments are significantly > >> overlapping - such that all three - ABC - have, say, at least the same > 7cM. > >> You can accept a little less overlap, by accepting a little more risk > that > >> it's not right. With so much randomness in atDNA, we cannot guarantee > >> anything. > > > > ______________________________ > For answers to Frequently Asked Questions about mailing lists, please see: > http://dgmweb.net/MailingListFAQs.html > > > ------------------------------- > To unsubscribe from the list, please send an email to > AUTOSOMAL-DNA-request@rootsweb.com with the word 'unsubscribe' without > the quotes in the subject and the body of the message >

Karen I don't understand "under 7cMs matches that match only me on a > > Chromosome". At FF and GEDmatch you can get shared segments down to 1cM. Both you and your Match get exactly the same string of ACTGs, and so get a matching segment. At GEDmatch you can compare yourself 1-to-1 to anyone else there - and you can set the threshold at 1cM. It is not unusual to compare to someone who is not a Match by most algorithms, and get 10-20 small matching segments. Most of these will be IBS segments - made up by individual ACTGs from both your parents to match someone else's combination. Or it could be pieces from each parent that match someone else's pieces. As you get segments over 7cM, it's somewhat harder to mix and match like this and wind up with a match - so the larger shared segments tend to be IBD - in tact chunks directly from a Common Ancestor. And yes, when you form a Triangle of Matches, the odds are much better that the segments are IBD. And if a shared segment can't Triangulate on either parent's Chr, it's probably an IBS segment. Jim - Sent from my iPhone - FaceTime! On Oct 19, 2013, at 5:14 PM, Karen Hodges <rowantreek@gmail.com> wrote: > Hi Jim > > That I understand. Its the under 7cMs matches that match only me on a > Chromosome. I guess these are best put aside if there is no genealogy > connection. Or two other matches come up in the same area for comparison > to determine IBD or IBS. > > Karen >