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DNA - Who do I test?

   Back in May I attended the Chromosome Mapping Workshop at the NGS Conference in Ft. Lauderdale.  Having been away for a month, I’m just getting back to putting what I learned to work.  Let me say, that if you are a DNA expert, you’ll probably find this a bit simplistic, but it’s taken me a while to get to this point, and as I talk with others at lectures, I don’t think I’m alone.  

   The first DNA test I took was back in 2010 with 23&Me and I was more interested in the medical aspects of the test than genealogy.  Tracking our families’ health history was always an interest for me and I’ve written about it a number of times.  If you’ve followed this blog for any amount of time, you’ll recognize the “Thanksgiving Day is Health History Day,” annual blogs, but that’s another issue.  I have close to 800 cousin matches at 23&Me, however the top two have posted no information and don’t respond to email.  One of the issues here is that many others have also tested for medical reasons and have no interest in genealogy.   On Ancestry I have 112 pages of matches (and if it’s like the 50 on the first page, that would be 5600 matches), and on FamilyTree DNA 929 matches.  I need to look at some of these!

   In his blog at Lost Cousins,  Peter Calver posted a chart showing  how many potential cousins you might have.  Using averages the chart projected that you might have 5 first cousins (I guess he wasn’t talking about Irish 😃), 28 second cousins, 175 third cousins, 1570 fourth cousins and by the time you get to fifth cousins, there could be as many as 17,300. Well, I don’t have anywhere near that number of people in my database, and most of my matches fall into the third to six or greater cousins.  Once you get past second cousins, the number of “detectable” cousins through DNA will begin to drop because of the way autosomal DNA passes down.  No wonder I don’t recognize any of the names!   Most of these people are distant cousins probably descended from a distant ancestor 5 or 6 generation back.  

   In Blaine Bettinger’s course for the Virtual Institute, (Finally!) Understanding Autosomal DNA, (which I highly recommend) he uses a graphic to show how parts of your Genetic Family Tree (as opposed to your Genealogical Family Tree) will start to disappear.  You receive (approximately) 50% of your DNA from your father and 50% from your mother; 25% from your grandparents; 12.5% from your great grandparents; 6.25% from your great great grandparents, etc.  In each case, the actual DNA will vary…you and your siblings might inherit different portions of your parents’ DNA (unless you’re identical twins).  So as the percent inherited gets smaller and the number of generations increases some of your genetic ancestors will disappear from your DNA.  

   So back to the numbers…my Dad had one brother who had three children and my Mom had two sisters who had a total of four children.  I have seven first cousins, and I know all of them.  We share the same four grandparents.  I have eight great grandparents and according to my genealogy software I have twelve second cousins.  I know that’s not all, because I only know of one sibling of my grandfather who was born in the Ukraine.  I know nothing about my great grandmother’s family.  And even as I go through my other great grandparents, I think I have all of their children, but not their grandchildren.  Why is this important?  Because I’m looking for 2nd cousins to test.

   So far, I’ve tested my siblings and a maternal first cousin.  I know that the DNA we share comes from our maternal grandparents.  I’m waiting for the results from a paternal first cousin, which will tell me what DNA we’ve received from our paternal grandparents.  The next step is to find a known second (or third) cousin descended from each of my great grandparents.  Each addition will allow me to futher identify the DNA I’ve received from each grandparent.  The reason I’m doing this is so when I look at my cousin matches and compare where we match, I’ll have some idea on what part of my family we’re related.  It’s like putting the pieces of a jigsaw puzzle together!

     The class I took at NGS was given by Angie Bush, and the tool she used for the class was Kitty Cooper’s mapping tool. The complete instructions for using the tool are on her website.  If you’ve tested at 23&Me or FamilyTree DNA you can directly download your results into a spreadsheet and create your map.  If you’ve tested with Ancestry (which doesn’t have a chromosome browser tool) you need to download your results to a free tool called GEDmatch from which you can proceed to the mapping tool. 

A video on GEDmatch basics from Angie Bush

   Hopefully this provides you with a few more pieces of the information to help get you started with DNA.

   Happy Hunting!


Check out The Genealogy Guys this week to hear the interview I did with Drew Smith for his new, Genealogy Connections podcast.

Fuel the Find!
Don’t forget the Worldwide Indexing Project July15-17.

© Donna M. Moughty 2007- 2017