Saturday, January 13, 2018

Genetic Genealogy When No Paternal Relative Is Available

Genetic Genealogy When No Paternal Relative Is Available 

County Meath
In genetic genealogy surname studies we use the Y chromosome in our DNA tests.  This chromosome is only passed from father to son and this is why this test is used in surname studies.  There are two sex chromosomes, X and Y.  Every person has one pair of sex chromosomes in each cell.  This is the 23rd pair, i.e. the sex chromosomes, which determine if you are male or female.  The Y chromosome is present in males.  Males have one X and one Y chromosome.  Females have two X chromosomes. The Y chromosome is the perfect tool to research family history and genetic genealogy, because it can follow a direct paternal line.

Women, and men that are researching a line other than their direct paternal line, cannot use a Y chromosome test.  But, there is another way to locate the Y chromosome data that you need for your research.

We use an autosomal DNA (atDNA) test to locate a match to a man from the line being researched.  We can then use this man's existing Y chromosome result or have him test to obtain this.  When an atDNA match is located and confirmed that it is the needed male line, you are good to go with your research using this proxy Y chromosome.

For example, I researched my father’s mother’s father’s line.  I carry their atDNA, but because this was not a direct paternal line I could not use my Y-DNA result.  I had already researched my father's paternal line using Y-DNA. Using this Y-DNA I located my cousins in Ireland and have been over to visit and found the family's progenitor in the primary sources.  The research was a complete success.   

the castle of Iníon Dubh, Porthall, Donegal
My father’s mother’s father’s line was also from Ireland. Their surname is Tweedy, however,  I do not carry the Tweedy Y-DNA.  I do carry the Tweedy atDNA DNA.  I used an atDNA test to locate a match to my Tweedy line.  I was hunting for a male Tweedy from that line and have him proxy Y-DNA test for me.

I did the Family Tree atDNA test which they call their Family Finder test.  Through this test I located a female Tweedy cousin and her father was a Tweedy.  She had a brother and we had him do the Y-DNA test.  This way, both she and I, could use him as a Y-DNA proxy to for our research. We now had the needed Tweedy Y chromosome and to begin our research.  

We have many women that participate in Irish Y DNA projects.  As in my case, they can use a male relative to proxy test for them.  It is a simple technique to use atDNA to locate a male proxy to obtain the needed Y-DNA sample.  This method works with both women, and men researching a non-direct paternal line.

Autosomal DNA testing does have limitations.  As a research tool, it can only go back around five or six generations.  But, most people can locate the family line they need within this time frame.  In my case it was a fourth cousin match and the time connection was mid-1800s.
All you need is one good match to the family you want to research and then have a male in that family test their Y chromosome.  Once you get the Y chromosome, you are set.  The Y chromosome does not have time limitations, you will find close matches, distant matches, even very distant matches. Once the Y-DNA is confirmed, you can go on to STR and SNP (two types of Y-DNA) testing which will give you very detailed data that will confirm geographic location, family branches, clan connections, and even tribal histories going back several thousand years.

Barry R McCain (c) 2018

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