New to DNA testing and have been asked to take a test.

Question

Before there is a commitment by someone in the family to take a DNA test requested by another family who is a guest on WikiTree I have a question as we are unfamiliar with this aspect of genealogy research.  Have been reading about the various tests and was wondering if the Family Finder test would help to confirm or deny a family relationship where one line (male) would be testing to see if his paternal Great Great Grandfather is the same man as the Great Great Grandfather of a female testing?

The female has a paper trail, her Great Grandmother is the daughter of her Great Great Grandfather.  The male has a paper trail which stops with his Great Grandfather.  It is only family lore who the father of his Great Grandfather is and he'd like to be able to confirm or deny this story.

Any thoughts on this would be greatly appreciated!

Answer 1

Autosomal DNA testing of both people ought to help answer your questions. People who share the same 2G grandfather are third cousins and should share autosomal DNA (if I remember correctly, the match is about 1%).

Comments

Thanks Ellen!

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About 90 percent of third cousins will share enough autosomal DNA to be detected. https://www.familytreedna.com/learn/autosomal-ancestry/universal-dna-matching/probability-relative-share-enough-dna-family-finder-detect/

On average the amount of shared DNA between third cousins will measure 53.13 cM.  See http://www.isogg.org/wiki/Autosomal_DNA_statistics

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Peter - Have read both links you posted and thank you..  I understand much more about the three types of DNA tests mentioned to me.

Answer 2

Both male and female offspring inherit mtDNA from their mother.

A son will not be able to pass on his mtDNA, so all children would inherit his wife's mtDNA.

Males pass along their Y-DNA to their sons only.

So, a girl, would have the same mtDNA as her mother's straight maternal line. A boy would have the same Y-DNA as his father, paternal grandfather, paternal great grandfather and so on.

Comments

Frank - I did understand about the female inheriting the DNA from her mother and so on down the line.  And the male inheriting the DNA from the father. I wasn't sure about the Autosomal test, though after reading your explaination I see that the test would not prove or disprove the fellows family lore based on the way DNA is passed on.   Thanks so much for clearing this up for me.

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It was interesting to me that my father's paternal line goes back to the same county in England as my mother's maternal line. The timing was different, my mother's ancestor from Norfolk County, England came to America in the early 1600's and my father's ancestor came over in the mid to late 1700's.

Answer 3

How important is this to him and how much patience does he have? These two questions have a direct correlation to how much will it cost.

If there is no relationship, that is there are no segments of any length in common, then there is most probably no relationship between these two cousins. Technically, in this case you still don't know if there is a problem with her tree or his, but we could probably rely on hers being valid.

If there is some relationship, then you can say that he shares at least one common ancestor.  Technically it could be either the 2nd great-grandfather or the 2nd great-grandmother, but it could also be both.

If money were no object, I would have him test at all 3 major autosomal services, and get a yDNA and mtDNA test(for his mother's side) first. I would test her on one of these sites.

Otherwise, I would test at AncestryDNA and have his tree online. He would look to see if any of his matches trees will help him. I would then transfer the Raw Data to FTDNA.

I do think he will find his answer if his female cousin also tests, preferably using the same service.

I would also test his Y-STR at FTDNA, at any level.  He can always upgrade later.

Comments

Ken, it is only family lore this fellow has as to even a name for his GGGrandfather.  We have never heard of or met him, he contacted our family only because of a similarity in the name which he saw online.  There is no connection to our GGGrandmother as she was not the mother of the child so if the test did show a relationship it could only be through the GGGrandfather.    Thanks much for your input.

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Joanne, I think we are on the same page. The short version of my response is that he certainly should purchase a test or tests to answer his question.

Forgive me if you already know this, but a very, very common misunderstanding  with autosomal testing (23andme, AncestryDNA, and Family Finder) is that it only works at finding relatives on either the male side or the female side.  I mention this only because I see one side of your family in your tree. These tests will find all close relatives however they are related to you.

There are two reasons you should test yourself.

1. Testing will help you validate (or invalidate) your tree.   I realize that your confidence level is high by having a well-documented tree, but errors do occur, some are even intentional given the number of NonPaternal events that keep cropping up.  I know this from experience.

2. This is somewhat philanthropic.  It will help others, if not now, certainly in the future, find the connections they are missing.

It can be pretty exciting to find cousins you never knew about and then work together to find how you are related.