DNA Testing - to determine second cousins?

[AngelaR]

I'd be really glad if people with any experience of DNA testing could advise on my current interesting problem.

I've very recently found several second cousins, all apparently descended from my grandmother's brother, Tom. However, one of Tom's daughters was told by a sibling later on in life that Tom wasn't really her father at all.  This lady's children and I are now in touch. I've never done DNA testing at all. Could anyone please offer an opinion as to whether

a) DNA testing could easily establish whether we were genuine second cousins or not
b) whether this would be prohibitively expensive to do.

Tom's 'daughter' died recently still not knowing whether tom was her father or not. It would be nice to get a clearer picture for her descendents.

By the way - the birth certificate is no use - Tom is quoted as the father.

Thanks very much for any advice you feel you can offer.

Angela

[Just Kia]

Y-DNA is passed unchanged from father to son, although mutations occur - which is what helps narrow down the common ancestor.

While mt-DNA is passed from the mother to all of her children, mutations are rare and so a close match is more likely but of less use - because more people are likely to have a close match and the common ancestor could easily be many more generations down the line.

The Y-DNA can only follow the direct male line - father - grandfather - great grandfather and so on. Only males can take the Y-DNA tests.
The mt-DNA can only follow the direct female line - mother - grandmother - great grandmother. Anyone can take the mt-DNA tests.

If I understand your question correctly then the standard genealogical DNA testing will not be able to give you a yay or nay because Tom's "daughter" would not have Y-DNA from her father and her mt-DNA would have come from her mother. There is also the problem of obtaining and using DNA from a deceased person. Of course you can't presume that her siblings had the same father.

However, paternity DNA tests look at different parts of the DNA (there is a way to test DNA for paternity of a daughter, otherwise how would they do it in cases of child support etc).
a) I do not believe DNA testing could easily establish whether you are/were genuine second cousins, but that it probably can on some much more complex level.
b) Cost would probably be quite high as the standard FH type DNA tests would not answer your question.

[charlotteCH]

Hi Angela
You ask about cost. I know next to nothing about the technical side of this- ask JustKia for that- but I paid for a DNA test on one person in the male line one of my lines and that one test cost $150 US.
It was part of a bigger test of many males and that may have affected the price.

charlotte

[AngelaR]

Hi JustKia and Charlotte

Thank you very much for the information. I know a tiny bit about DNA and nothing at all about current tests so that is very useful indeed.

It looks these checks are a non-starter in this situation so we don't have to waste time/resources going down this route 

I really appreciate your help, so thanks a lot to both 

Angela

[DevonCruwys]

Angela

The new Family Finder test from Family Tree DNA would tell you whether or not two people are second cousins. The test has only just been launched today. My dad has been in the beta-testing programme and I've done a write-up on my blog with a few screenshots explaining how it works:

http://cruwys.blogspot.com/2010/04/new-family-finder-test-from-ftdna.html

FTDNA also have a very good FAQ page here:

http://www.familytreedna.com/faq/answers/17.aspx

The test costs US $289 so it would be quite expensive to get two people tested.

Another company called 23andMe offer a similar test called the Relative Finder which would also answer this question. Their test costs $399 (Ancestry Edition):

https://www.23andme.com/

Debbie

[coombs]

I have thought of DNA testing before but I did hear that it would only work for my y line and my mt-DNA line. I have made contact with a 6th cousin though our direct paternal lines and we should share the same Y DNA.

[charlotteCH]

Of course all this assumes no adultery enroute

charlotte

[Just Kia]

Debbie, that's great info.
I hope this can be added to the lexicon.

[AngelaR]

Sorry, only just logged on, so a bit late in giving my thanks to Debbie 

That is most interesting information, Debbie so thanks very much! I'll tell my putative second cousins about it and see what they think. It's a bit too expensive for me to go down that route, but for all I know they might be rich 

Thanks again everyone for your contributions to an area about which I knew absolutely nothing

Angela