Tim, if I were to test my son and his mother, we would be able to phase our data. Would that then allow me to better evaluate my own matches as well as my sons? I've always basically skipped over discussions of phasing because, since my parents are both deceased, I just figured this was something that didn't apply to me. But perhaps it would be allow for partial understanding of my own atDNA by doing as I suggested above?? So any segments that my son has that came from me and pass the phasing test would therefore also be proven IBD segments for me as well. So I guess roughly 1/2 of my atDNA would be assessable by this method? On Sat, Jan 7, 2012 at 2:09 AM, Tim Janzen <[email protected]> wrote: > Dear Jim, > I agree that it pays to concentrate on your matches at either FF or > 23andMe that are over 10 cMs. If you chose to contact people who are > matching you at less than 8 cM or so you need to keep in mind that a > significant percentage of these matches will be IBS unless one of your > children also matches them on the same segment, in which case they will be > IBD. > Ideally, you would like to phase your data and then compare your > phased data to that of your matches. The only way you can do that is to > test two parent/one child trios and then use a phasing program like the one > I wrote or David Pike's to compare your phased data with that of your > matches. In order to do this, your matches would need to share their raw > data file with you. I suspect that many people won't be willing to do > that. > Ideally everyone would be downloading their raw data files and uploading > them GEDmatch where you could do comparisons using phased data. So far > neither 23andMe or FTDNA have made a move to phase their data. I talked to > Bennett Greenspan about doing this for Family Finder in November, but he > was > reluctant to spend the money on the programming needed to phase the data > for > the two parent/one child trios that he currently has in FF. > As I have mentioned before, we all need to be mapping our > chromosomes so we know as best as possible which ancestral line each DNA > segment came from. In your particular case, you have quite a few matches > who could be distant cousins (6th-10th cousins). What you need to do is > test as many 2nd and 3rd cousins as feasible from the lines you think you > match your other distant cousins on to see if the DNA segments you share > with those distant cousins came through the ancestral lines you think they > could have come from. Using phased data for doing the comparisons would > also be of big help to you if you could get your matches to share their raw > data file with you. You could then quickly tell which of your matches are > simply IBS. > Sincerely, > Tim > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Jim Bartlett > Sent: Friday, January 06, 2012 10:20 PM > To: [email protected] > Subject: Re: [AUTOSOMAL-DNA] SUBJECT: How do you work a 5 way FF match with > few clues ? > > Tim, > > Walden's table looks very similar to the percentages that FTDNA uses to > indicate what percentage of your cousins will show up as a match with > Family > Finder... Are these the same? This would mean most of your cousins would be > listed, but a percent would be IBS, and so not atDNA cousins. I don't think > this is the case because I have a number of known cousins, with atDNA > tests, > who do not match me (FF or 23) > > So the other option is that FTDNA's percent eliminates some of your cousins > from appearing on the match list, and Walden's table eliminates a > percentage > of these from being atDNA cousins. This is really whittling down the true > matches. And worse yet, the unphased don't know which are which. > > If I do understand this, we can't rely on the list from, say, FTDNA. We > need > to manually?, or with some software, determine if the A in AG is from Mom > or > Dad, and do this for our whole raw data (how many ACTGs?). And then how do > we compare this with the long segments of our matches? Is this part of the > FTDNA and 23&me programs I haven't found yet? Or do I need 3rd party help. > > Now I'm just trying to see how I get this info, and then how I use it with > my list of matches to capture the ones who are IBD. I guess one way is to > cull out everyone below 10cM. Now I'm catching on. But this will eliminate > most of my matches... It also covers a number of folks with whom I've > already found common ancestry - the point here being that we might be > cousins, but we probably don't share a large IBD segment... > > Jim - > > > > ______________________________ > 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 > [email protected] with the word 'unsubscribe' without > the quotes in the subject and the body of the message >

Dear Dwight, Keep in mind that one of your long term goals needs to be to figure out which portions of your DNA came from your mom and which portions came from your dad. The more of your DNA you can categorize in this way then they easier time you will have eliminating portions of your pedigree chart from consideration when you are evaluating your matches. Simply having your son tested would help you sort out a significant percentage of your matches that are IBD. Testing his mother as well would help you phase your data so that you could run comparisons of your phased data against the raw data files of any of your matches who are willing to share their data file with you. If you test your son you would expect that about 50% of your matches would also share the same segment with your son, assuming that all of your matches were IBD. Unfortunately, we know that all of your matches aren't IBD. Let me provide further data that compliments that statistics that John Walden generated. This summer I downloaded all of my mom's and my Family Finder matches. I then categorized all of my mom's matches as to whether or not I also shared the same segment with her matches. Here are my statistics: 1. For my mom's matches that were over 10 cMs, I was a match to 22 of her 47 matches, or about 47%. This is slightly under the expected percentage of 50%, but in general this helps confirm John's statistics that about 99% of matches over 10 cMs are IBD. 2. For my mom's matches that were between 9 and 10 cMs, I was a match to 7 of her 18 matches, or about 39%. This is somewhat under the expected percentage of 50%. 3. For my mom's matches that were between 8 and 9 cMs, I was a match to 9 of her 34 matches, or about 26%. This is significantly under the expected percentage of 50%. 4. For my mom's matches that were between 5 and 8 cMs, I was a match to 12 of her 21 matches, or about 57%. This is significantly higher the expected percentage of 50%. 5. For my mom's matches that were between 3.5 and 5 cMs, I was a match to 29 of her 73 matches, or about 40%. This is significantly lower the expected percentage of 50%. My data doesn't look quite as striking as John's does for the percentage of matches that are IBS that are less than 8 cMs, but it does indicate that in general a significant percentage of matches between 3.5 and 10 cMs will be IBS. When I have more time I will try to generate more data from both FF and 23andMe on this topic. Sincerely, Tim -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Dwight Holmes Sent: Friday, January 06, 2012 11:18 PM To: [email protected] Subject: Re: [AUTOSOMAL-DNA] SUBJECT: How do you work a 5 way FF match with few clues ? Tim, if I were to test my son and his mother, we would be able to phase our data. Would that then allow me to better evaluate my own matches as well as my sons? I've always basically skipped over discussions of phasing because, since my parents are both deceased, I just figured this was something that didn't apply to me. But perhaps it would be allow for partial understanding of my own atDNA by doing as I suggested above?? So any segments that my son has that came from me and pass the phasing test would therefore also be proven IBD segments for me as well. So I guess roughly 1/2 of my atDNA would be assessable by this method?

So, a couple questions here .... good thread by the way.    This is really helpful.   Complicated but helpful none-the-less. First .... if I can test my brother, my father and myself how much of my mothers atDNA (for FF purposes) can I tease out of the mixture?    Second .... the percentages mentioned that John Walden has brought forward (and your observations as well Tim) apply to a single segment of DNA being compared to a similar but likewise single segment of DNA ..... do they not?  However, in many to most of these reported or observed "cousin" situations with segments less than 8 cM ... heck ... less than 7 cM for that matter .... we "normally" have multiple "matching" segments.   Those phasing percentages therefore apply independently to each paired observation as I understand it and therefore the probability that one or more of say 14 matching segments is IBD vs IBS approaches 1 quite quickly.   Is that an accurate assessment?   I'm not saying that these are matches that can be determined in a genealogical timeframe but I'm just trying to understand whether this is an ALL or NOTHING situation .... I don't believe it is.    John 

Dear John, If you have a two parent/one child trio and you phase the data you should be able to figure out about 83% of the mother's DNA. If you have a two parent/two child quartet and you phase the data you should be able to figure out about 95% or more of the mother's DNA. It becomes much more challenging when your mom's data isn't available for testing. If your dad and you were both homozygous for a specific SNP (say AA and AA), then you would know that you got an A from your mom, but you wouldn't know what the other allele your mom had unless your brother got a different allele than you did, in which case you would know the two alleles that your mom had for that SNP. If you have any children, I would suggest that you test your wife and your children. This would allow you to phase your data. You can then use your phased data to phase your dad's data. If you have phased your data then you will have 50% of your mom's data and that portion will be phased. If your brother has a! ny children, I would also test your brother's children and his wife. This would allow you to phase your brother's data. You can then compare it to your dad's data which would in theory give you an additional 25% of your mom's data, raising the total of your mom's phased data to about 75% of what she had originally. I am not sure that there is an easy answer to your 2nd question. Simply having multiple people who match with you on a specific segment of DNA segment (say a 7 cM segment) doesn't necessarily imply that the segment is IBD. If you have a child who also matches with these other people at that segment, then it is for all practical purposes IBD, but I could caution you not to jump to the conclusion that you have an IBD segment just simply because multiple people match you on that segment. Also bear in mind that if you have multiple matches on a particular segment that some could be IBD and some could be IBS. You can't really be sure which is which without phasing your data and then running the comparison. Sincerely, Tim Janzen -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of John F Smeltzer Sent: Saturday, January 07, 2012 4:30 AM To: [email protected] Subject: Re: [AUTOSOMAL-DNA] SUBJECT: How do you work a 5 way FF match with few clues ? First .... if I can test my brother, my father and myself how much of my mothers atDNA (for FF purposes) can I tease out of the mixture? Second .... the percentages mentioned that John Walden has brought forward (and your observations as well Tim) apply to a single segment of DNA being compared to a similar but likewise single segment of DNA ..... do they not? However, in many to most of these reported or observed "cousin" situations with segments less than 8 cM ... heck ... less than 7 cM for that matter .... we "normally" have multiple "matching" segments. Those phasing percentages therefore apply independently to each paired observation as I understand it and therefore the probability that one or more of say 14 matching segments is IBD vs IBS approaches 1 quite quickly. Is that an accurate assessment? I'm not saying that these are matches that can be determined in a genealogical timeframe but I'm just trying to understand whether this is an ALL or NOTHING situation .... I don't believe it is. John

Tim - This is incredibly useful information and I can not imagine how many hours you put into to arriving at these statistics!! Most of all, I want to say I find this very encouraging, really. Based on recent threads and information on this topic (the high likelihood of segments <10cM being IBS) I have increasingly been ignoring matches that are based on a longest segment of less than 10cM. But if I take your last two categories and combine them, you have found that you match 44% of your mother's matches in the range between 3.5cM and 8cM! Below the 'expected' 50% yes, but seriously that is a much more optimistic picture than what I had come to believe was true. Those under 8cM odds really aren't all that different from the over 10cM odds: 44% vs 47% (50-44% vs 50-47%, actually). Which says to me - and please tell me if you take a different lesson from this - all this really says is that there is no certainty in this - and we knew that! Treat every DNA match as a potential genealogical match and see what you find! On Sat, Jan 7, 2012 at 2:58 AM, Tim Janzen <[email protected]> wrote: > Dear Dwight, >        Keep in mind that one of your long term goals needs to be to figure > out which portions of your DNA came from your mom and which portions came > from your dad.  The more of your DNA you can categorize in this way then > they easier time you will have eliminating portions of your pedigree chart > from consideration when you are evaluating your matches. >        Simply having your son tested would help you sort out a significant > percentage of your matches that are IBD.  Testing his mother as well would > help you phase your data so that you could run comparisons of your phased > data against the raw data files of any of your matches who are willing to > share their data file with you.  If you test your son you would expect that > about 50% of your matches would also share the same segment with your son, > assuming that all of your matches were IBD.  Unfortunately, we know that all > of your matches aren't IBD.  Let me provide further data that compliments > that statistics that John Walden generated.  This summer I downloaded all of > my mom's and my Family Finder matches.  I then categorized all of my mom's > matches as to whether or not I also shared the same segment with her > matches.  Here are my statistics: > 1.  For my mom's matches that were over 10 cMs, I was a match to 22 of her > 47 matches, or about 47%.  This is slightly under the expected percentage of > 50%, but in general this helps confirm John's statistics that about 99% of > matches over 10 cMs are IBD. > 2.  For my mom's matches that were between 9 and 10 cMs, I was a match to 7 > of her 18 matches, or about 39%.  This is somewhat under the expected > percentage of 50%. > 3.  For my mom's matches that were between 8 and 9 cMs, I was a match to 9 > of her 34 matches, or about 26%.  This is significantly under the expected > percentage of 50%. > 4.  For my mom's matches that were between 5 and 8 cMs, I was a match to 12 > of her 21 matches, or about 57%.  This is significantly higher the expected > percentage of 50%. > 5.  For my mom's matches that were between 3.5 and 5 cMs, I was a match to > 29 of her 73 matches, or about 40%.  This is significantly lower the > expected percentage of 50%. > > My data doesn't look quite as striking as John's does for the percentage of > matches that are IBS that are less than 8 cMs, but it does indicate that in > general a significant percentage of matches between 3.5 and 10 cMs will be > IBS.  When I have more time I will try to generate more data from both FF > and 23andMe on this topic. > > Sincerely, > Tim > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Dwight Holmes > Sent: Friday, January 06, 2012 11:18 PM > To: [email protected] > Subject: Re: [AUTOSOMAL-DNA] SUBJECT: How do you work a 5 way FF match with > few clues ? > > Tim, if I were to test my son and his mother, we would be able to phase our > data. Would that then allow me to better evaluate my own matches as well as > my sons? I've always basically skipped over discussions of phasing because, > since my parents are both deceased, I just figured this was something that > didn't apply to me. But perhaps it would be allow for partial understanding > of my own atDNA by doing as I suggested above??  So any segments that my > son has that came from me and pass the phasing test would therefore also be > proven IBD segments for me as well. So I guess roughly 1/2 of my atDNA > would be assessable by this method? > > > > ______________________________ > 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 [email protected] with the word 'unsubscribe' without the quotes in the subject and the body of the message