DNA Confirmation advice

[Darryl Stearman]

This question definitely needs advice from someone who ha been there/done that:

My Grandfather was born into illegitimacy, taking his mothers maiden name in 1922, nothing unusual there i suppose.

Through research i have identified his (potential) Father and my G Grandfather, of course no longer with us.

I have met a male descendant, same generation as me so both male line G Grandsons of Mr X

By my limited calculation, we both shoul share 12.5 % DNA the same if we share a common G Grandfather.

My question(s) are

1: is that correct, would we share 12.5% assuming we both had direct lineage and no "breaks" in our chains, and

2: Has anyone got advice on how to go about researching a DNA service provider to do  test. we are both keen to see if we do share this ancestor, so we can both supply a test.

Any thoughts ?

 

[behindthefrogs]

If you are both descended down a purely male line from the common G Grandfather you should be able to get a close match not 12.5%.  If there is a female in either line excluding yourselves then it is very difficult.

David

[Darryl Stearman]

Thanks David, we ca both confirm (assuming truth be told) that our G Fathers, Fathers and we two are direct links.

Can you expand on your point about close match, wha do you mean by close match? is this a type of test that we require?

[behindthefrogs]

A Y chromosone DNA test is used to confirm direct male descendancy.  In the case of general proof for a surname 25 markers are usually recommended as the minumum but in your particular case the minimum number of 12 markers used in basic paternity tests might be sufficient.  It all depends on how much you want to pay.

Why I said a close match is because each generation can introduce some mutation of some of the markers.

The science is described at

http://en.wikipedia.org/wiki/Genealogical_DNA_test

For a test on the female line the mitochondrial DNA is used.

David

[Adnepos_Iacobi]

Hi Darryl

Your genetic genealogy question has a more straightforward, neater, resolution than the one that you propose. So I'll recommend the approach you take and only then comment on the 12.5%.

If your deductions are correct, both you, your putative great grandfather and his second living relation will have essentially identical Y chromosomes. The two of you can have Y-DNA tests and if you are both all-male line descendants of the same great grandfather, then the markers will be identical -or at a very outside chance, just one difference in just one of the markers. You could both order the basic 12-marker test but it is not offered any more by most companies. Most offer a test with about 40 markers and this would be good value -expect to pay just short £100 each. Companies also offer tests with more markers but for your purposes, I think this would not be needed. You can always upgrade and get other genetic genealogy tests done from the same sample if you become interested in the subject.

Different companies report Y-DNA results is slightly different ways. The results from one company can be converted to those for another but I'd recommend you both have the test done by the same company to simply matters.

There are many companies that offer Y-DNA tests. By far and away the biggest is Family Tree DNA but there is also dna.ancestry (used to be called Relative Genetics), DNA Heritage, EthnoAncestry, familybuilder, Genebase, GeneTree (I used them because they offered the best deal at the time), Oxford Ancestors, Pathway Genomics, Personal Genome Project and Trugenetics. There are more. Check them out on the internet and compare costs and the extra features that some companies offer. Check for surname projects - Family Tree DNA will offer a discount if you have your tests done under such a project. You may get a discount and/or extra features for having a pair of tests done together.

You are right that if you don't share any other recent ancestor, then you will share about an eighth of your autosomal (non Y-, non X-chromosome and not mitochondrial) DNA. It would be less helpful and more expensive to  test your autosomal DNA although the results would probably be more exciting! If you want excitement look at the tests offered by 23andMe and deCodeME.

[Darryl Stearman]

Thank you for that thorough explanation of how descendant DNA works and how it can be exploited in the Family Tree context. £100 each seems ok and a good reference when checking out which company to use.

i was thinking of doing these tests as a stand alone examination but you mention other ways to exploit the results in one world tree type data bases. are there ways then to log the results so that later on others may make Family matches etc to bring together other researchers?

Currently i use Ancestry as my base research provider, they have a DNA tab so i may follow that to see if thats any good.

[Adnepos_Iacobi]

Hi again, Darryl

I think Family Tree DNA has the biggest Y-DNA database but they also sponsor an open database -ySearch- that is pretty big too.

[Darryl Stearman]

Thanks again, i will check out the Family Tree site.

[DevonCruwys]

The best test for this purpose would  be the new Family Finder test from Family Tree DNA which has just been launched today. My dad was in the beta-testing programme and I've done a write-up on my blog with screenshots showing how it works:

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

Debbie