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Sisters

Posted: 16 May 2015 12:15AM GMT
Classification: Query
Using Ancestry autosomal test can two sisters tell if they have the same father? If so how? What would you compare?

Re: Sisters

Posted: 16 May 2015 1:47AM GMT
Classification: Query
If you have the same father, you will each have received the same X chromosome from him since he has only one. You may have gotten the same or different X's from your mother since she has two to chose from. So you need to upload both your DNA results to GEDMATCH and see what that can tell you.

Re: Sisters

Posted: 16 May 2015 1:49AM GMT
Classification: Query
If you could test your father and/or your mother, that could help you pin it down further.

Re: Sisters

Posted: 18 May 2015 10:49PM GMT
Classification: Query
Also, after uploading to GEDMatch, you'll see the amount of shared DNA. I think full siblings share somewhere around 2600cM, half-siblings around 1700cM.

Re: Sisters

Posted: 19 May 2015 5:28PM GMT
Classification: Query
Once you upload your results to Gedmatch and see your shared cMs it will be apparent. Here's a good article on Autosomal DNA statistics.
http://www.isogg.org/wiki/Autosomal_DNA_statistics

Re: Sisters

Posted: 20 May 2015 12:46AM GMT
Classification: Query
Thank you for the replies. There is no one left to test beside the two sisters. They know they have the same mother but strongly suspect a different father. They have not done any DNA test yet. I was trying to see if it could be done with a autosomal test.

Re: Sisters

Posted: 16 Jul 2015 4:49AM GMT
Classification: Query
Yes, an autosomal test can tell you if they share both parents or only one parent. If you compare the two sets of results on a site like gedmatch, you will likely see many double-strand matches across the chromosomes if they share both parents. But you will see only single-strand matches if they share just one parent.
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