GENEALOGY-DNA-L ArchivesArchiver > GENEALOGY-DNA > 2010-03 > 1268815198
Subject: Re: [DNA] need 23 and me assistance
Date: Wed, 17 Mar 2010 04:39:58 EDT
Females have two X chromosomes, one inherited from the father and the other
from the mother, so a connection could be from either side of the family.
Males have one X chromosome, inherited from the mother. SMGF has a nice
animation showing the inheritance pathway:
Since not all ancestors can make a contribution to the X, you can eliminate
at least some of them as possibilities. See the diagrams on Blaine
Note that the percentages are AVERAGES. A man's X chromosome can be exactly
the same as his maternal grandfather, exactly the same as his maternal
grandmother, or a mixture of the two, which works out to be average of 50%. I
find the demo Mendel family at 23andMe helpful in visualizing this. There are
three grandchildren and three grandparents, so you can look at different
combinations. If they don't show up in your list of people you're sharing with,
go to Account | Sharing | Example Profiles.
If your genealogy program can print an ahnentafel chart, I've prepared a
file with the relevant ahnentafel numbers. Females should start the ahnentafel
with themselves; males should start with their mothers. Then you can go
through the ahnentafel report and delete the records of the people who could
not be the source of your X.
In a message dated 3/16/2010 10:22:51 PM Pacific Daylight Time,
> See chart at very bottom...
> so, I'm thinking that the colored areas are for the X chromosomes??