Maternal/Paternal relationship

[Jan M. Gronski]

I am not sure if this is the best place to pose this question, so please guide me to the correct Forum. I also think that there must have been discussions of this in the past, if so then please refer me to the right thread.

Here is the question:

Me and another person believe that we are related, however we think that the common ancestor comes from my maternal and his paternal side. What is the best way about checking if we are related?

-- jan

[cacio]

The standard tests discussed here won't work, because they require either purely maternal line (mtdna) or purely paternal line (Y chromosome). A couple of ways of going at this.

One would be to find a relative, eg a cousin. For instance, say the person you're thinking about is your paternal grandmother and his maternal grandmother. Perhaps your father had a sister, your aunt, and she had daughter. So this really depends on who's available or not.

The other way of going at this is to compute the amount of common DNA. The more related you are, the more common DNA you have. This test is not standard, and you'll have to ask some specialized lab. 23andme, as a part of their big test, also produce a gene comparison between two people. However, this method works only for close relatives. I am not sure you can go much further than a common grandparent. After that, the amount of common DNA decreases and becomes undetectable.

Perhaps if you specify the supposed relation more clearly, somebody could have better ideas.

cacio

[tomcat]

Unfortunately there is no quick way to test your relatedness unless your common ancestor lived in the recent past. Then you could each take the 23andMe genome scan and assess your degree of sharing across 600,000 SNP's. A portion of those SNP's are mitochondrial and y-chromosome so will not be mutually informative (www.23andme.com).

The more laborious genealogical approach calls for finding and testing cousins, aunts and uncles 'around' the common ancestor who received either the mitochondrion or y-chromosome of the common ancestor.

[Jan M. Gronski]

Thanks

Thank you for the advice. We are talking here about a fairly distant relationship. We suspect that our great grandfathers were brothers. I guess we will have to look for a common relative that would be connected on either maternal or paternal side.

-- jan

[cacio]

Great grandfathers is probably stretching a little bit the power of general DNA test. Since we're talking about males, your only hope is to find one purely male descendant for both line, just males, no females, and compare the Y chromosome.

This is more or less what the Jefferson researchers (of the Sally Hemings case) did - they located one male descendant of Jefferson's brother, and one male descendant of the Hemings.

cacio

[Jan M. Gronski]

I think that we have located a likely candidate, who is my cousin and is a descendant of yet another brother of my great grandfather. We only need to convince him that it is worth his while :-). Thanks for the advice.

-- jan