[Ferguson-dna] Suggestions for Using Gedmatch

Sharon Clark clarksha at verizon.net
Tue Apr 18 13:34:24 CDT 2017


When I first uploaded my raw data to Gedmatch, I had no idea what to do.  For several months, all I knew to do was to use the one-to-many search. Once I did that, I didn't know what to do with it.  Then I decided to try and learn more about it.

For those who tested at Ancestry DNA, you don't get a chromosome browser.  FTDNA and 23andMe give their customers chromosome browsers.  I tested at FTDNA but had no idea how to use a chromosome browser.  It is a spreadsheet showing all of your matches, and what chromosomes you match on.  Also, it shows the starting point and ending point for each segment you share DNA with your match.  You can download the entire chromosome browser at FTDNA.  Once you do that, you need to sort the spreadsheet by chromosome number and starting location.  Then, if you have a match with someone on a certain chromosome and the same start location, that means you share a common ancestor with that person.  Legitimate matches are supposed to be at least 7 cMs (centimorgans) and contain at least 700 SNPs.  (I never can remember what SNPs are.)  Ignore the matches less than 7 cMs and 700 SNPs, and concentrate on the larger numbers.

Since Ancestry doesn't give us chromosome browsers (I later tested at Ancestry, too), you can get the chromosome information through Gedmatch using the one-to-one search.  It shows the chromosome numbers and the start location of where the two of you match.

I also used the feature of finding those who match two different kits - I can't remember the exact title.  This feature produces a list of kits that match both kits, then a list of matches for kit No. 1 only, and then a list of matches for kit No. 2 only.  The first part, where it shows kits that match both kits, your matches might not be on the same chromosome and same start location. You would have to do the one-to-one search to see if you match on the same chromosome number, and at the same start location.

There is something called "crossovers" and I don't really understand that yet.  There is a wonderful blog, segmentology.org, written by Jim Bartlett, and it is very helpful. You might want to subscribe to that.  Another blog that is really helpful is:  https://dna-explained.com/   Roberta Estes is the author of this blog.
What is really great about Gedmatch are the Tier 1 features.  A few years ago, these were free, but you have to pay $10.00 a month for them now. I love the Segment Triangulation tool, and they have a new one, Triangulation Groups. If you want to try these tools, you could pay for a month and see if you think they would be helpful to you.
There is also a helpful list at Rootsweb, autosomal-DNA at rootsweb.com.  There are some extremely knowledgeable people on the list, and they try and help everyone.  If you join this list, send a query to the list and I am sure someone will help you with your Gedmatch questions.

You can also go through some of the Gedmatch Forums. You can find these on the page you get when you sign in.  Look on the left side of the screen, where it says Learn More.

I am certainly not an expert - in fact, I still feel like a beginner most of the time, but I hope this helps a little.

Best wishes,
Sharon Clark
Fort Worth, TX
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