I have a question. Its usually said that a HIR smaller than say 7 cM is frequently not really from shared descent. I presume this means that just by accident its half identical ... and that if we actually had truely phased (from a physical measurement, which I have of myself) data of one person we could be surer of a real match with the other person. This is because the "other person" would have some markers that are homozygous and don't match the same side as the supposedly matching side of me. I'm sorry if this is unclear, but that's the best I can say it. If indeed this is the case, then smaller segments should be "real". This is important since I don't have parents available to "genealogically" phase me, and have to use not coly close cousins but some more distant ones. How small a block should I trust, given that a different LARGE block on the other person has a known, triangulated relation to me, has the same relation to me? Doug McDonald

The table from John Walden shows the dropout rate when the other party is also phased: https://isogg.org/wiki/Identical_by_descent#False_positive_matches Ann Turner On Mon, Dec 3, 2018 at 9:47 AM McDonald, J Douglas <jdmcdona@illinois.edu> wrote: > I have a question. Its usually said that a HIR smaller than say 7 cM is > frequently not really from > shared descent. > > I presume this means that just by accident its half identical ... and that > if we actually had truely > phased (from a physical measurement, which I have of myself) data of one > person we could be > surer of a real match with the other person. This is because the "other > person" would have > some markers that are homozygous and don't match the same side as the > supposedly matching > side of me. I'm sorry if this is unclear, but that's the best I can say it. > > If indeed this is the case, then smaller segments should be "real". This > is important since I > don't have parents available to "genealogically" phase me, and have to use > not coly close > cousins but some more distant ones. How small a block should I trust, > given that a different LARGE > block on the other person has a known, triangulated relation to me, has > the same relation to me? > > > Doug McDonald > > > > _______________________________________________ > Email preferences: http://bit.ly/rootswebpref > Unsubscribe > https://lists.rootsweb.com/postorius/lists/genealogy-dna@rootsweb.com > Privacy Statement: https://ancstry.me/2JWBOdY Terms and Conditions: > https://ancstry.me/2HDBym9 > Rootsweb Blog: http://rootsweb.blog > RootsWeb is funded and supported by Ancestry.com and our loyal RootsWeb > community >

This article by Durand et al and others that reference it maybe of interest: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4104314/ On Mon, Dec 3, 2018 at 11:47 AM McDonald, J Douglas <jdmcdona@illinois.edu> wrote: > I have a question. Its usually said that a HIR smaller than say 7 cM is > frequently not really from > shared descent. > > I presume this means that just by accident its half identical ... and that > if we actually had truely > phased (from a physical measurement, which I have of myself) data of one > person we could be > surer of a real match with the other person. This is because the "other > person" would have > some markers that are homozygous and don't match the same side as the > supposedly matching > side of me. I'm sorry if this is unclear, but that's the best I can say it. > > If indeed this is the case, then smaller segments should be "real". This > is important since I > don't have parents available to "genealogically" phase me, and have to use > not coly close > cousins but some more distant ones. How small a block should I trust, > given that a different LARGE > block on the other person has a known, triangulated relation to me, has > the same relation to me? > > > Doug McDonald > > > > _______________________________________________ > Email preferences: http://bit.ly/rootswebpref > Unsubscribe > https://lists.rootsweb.com/postorius/lists/genealogy-dna@rootsweb.com > Privacy Statement: https://ancstry.me/2JWBOdY Terms and Conditions: > https://ancstry.me/2HDBym9 > Rootsweb Blog: http://rootsweb.blog > RootsWeb is funded and supported by Ancestry.com and our loyal RootsWeb > community >