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Old 30th August 2017, 03:54 PM
Oldcrone Oldcrone is offline
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A really stupid question

My two sisters and I all share X with a third cousin which comes from our father's line. Our common ancestors are our second gr-grandparents. On our side, this could only have come from our 2nd gr-grandmother since the generation before was our gr-grandfather. Does this mean that the 30 cM and 39 cM we respectively share with this cousin had to have come from our 2nd gr-grandmother?
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Old 30th August 2017, 06:34 PM
jova99 jova99 is offline
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yes

your logic is correct, since your Grandfather got his X from his mother and received no X from his father.
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Old 30th August 2017, 06:56 PM
prairielad prairielad is offline
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If referring to X segments only, this depends if each of your lines descends from their daughters or if at least one line descends from a son.
the shard autosomal segments (chr 1 thru 22) can be from either 2nd great grandparent. If you have more then one segment on the autosomal chromosome's one maybe from the 2nd great grandfather the other his wife.
Only on X can you say 2nd great grandmother IF at least one of your lines descends from a son (no X from father)
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Old 30th August 2017, 07:26 PM
Oldcrone Oldcrone is offline
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Quote:
Originally Posted by prairielad View Post
If referring to X segments only, this depends if each of your lines descends from their daughters or if at least one line descends from a son.
the shard autosomal segments (chr 1 thru 22) can be from either 2nd great grandparent. If you have more then one segment on the autosomal chromosome's one maybe from the 2nd great grandfather the other his wife.
Only on X can you say 2nd great grandmother IF at least one of your lines descends from a son (no X from father)
Thanks to prairielad and jova99 for their replies. The lines go from myself (or my sisters) to my father (Joseph Casey) to his mother (Philomen Casey) to her father, Andrew Casey to his mother Martha LeBlanc. On the third cousin's side it goes from her to her father (Milton Laughlin)to his mother, Margaret McDougall to her mother, Scholastique Caissie (there appears to be no link to her father) to her mother and father, Laurent Cassie and Martha LeBlanc. Therefore I assume the X chromosome came from Martha LeBlanc.
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Old 30th August 2017, 07:34 PM
prairielad prairielad is offline
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Since your line descends from the son, X match (only referring to X segments) will be from from your 2nd great Grandmother, as no X from Laurent Cassie would have been passed on to your line. Your second cousin could have X segments that match others that will match Laurent Cassie though, just not your line as mentioned, his X was not passed onto Your ancestor Andrew Casey, no male to male transmission.
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