Wednesday, February 22, 2017

23andMe Has The Best DNA Tools: Advice On How To Use Them

Chromosome map

The tools for working with matches at 23andMe are outstanding. The only drawback is the lack of response from matches. There are no trees at 23andMe, and few people have posted ancestral surnames. I'm finding, however, if I can find a common ancestor with a 3rd cousin match I can identify segments which lead to resolving how many of my matches relate to my mother and I.

I've been able to identify 3rd cousin matches by searching for trees at I search using the member directory. Most 23andMe matches don't have Ancestry trees, however. They generally don't have trees at MyHeritage either. Most testers at 23andMe have little ancestral information, if any at all.

The best way to ID 3rd cousin, or 2nd cousins for that matter, is compare segments using Genome Mate Pro, or a spreadsheet. If you compare your matches at 23andMe with GEDmatch cousins, for instance, you'll find matches who have tested at all 3 major companies. Since AncestryDNA matches often have some sort of tree you can sometimes find matches with trees who share the same segment, or overlapping segment, with a 23andMe match. You may then be able to identify these segments as coming from common ancestors.

You can compare segments with all your Family Tree DNA matches, if you've tested with them, or transferred your AncestryDNA raw data over to them. You will find more trees and surnames at Family Tree DNA than you'll find at 23andMe. You may find segment matches and common ancestors comparing here.

Once you have a map with identified segments 23andMe matches will be easier to identify, even if they aren't sharing with you, or open sharing. The relatives in common feature will allow you to identify matches. I didn't copy the names for privacy reasons in the screenshots below.

The first shot below is from the common relatives feature, at 23andMe, displaying matches shared with a match I selected. This match is a 3rd cousin. The shared matches are 3rd cousins with me; as stated below in the first column. The percentage of DNA shared with me is also given. Column two gives the relationship of these shared matches with the match I selected. The first common match is actually the mother of  the match I selected. The second common match is the uncle of the selected match, as stated below. The uncle isn't sharing with me, and has a different surname. I wouldn't have guessed their relationship with out the same surname. The fact the relationship is provided is so helpful. I have had contact with the person described as mother here. We have found common ancestors. So even without any surname information posted by these three I have determined how they are related. I have the shared segments for the mother and daughter and can marked them with the shared ancestral couples' surnames. These segments have helped me identify many more matches. I've been able to confirm some of these at, with trees. I don't have the uncle's segments, but know how he is related.


My mother and I don't have 2nd cousin matches at 23andMe so I'm focusing on 3rd cousin matches with substantial shared amounts of DNA. I'm using the large segments to infer how those sharing smaller segments might be related. Below you see a 3rd cousin match who is a 1rst cousin to the match I selected to compare with. This would definitely lead me to believe we three share common ancestors. Both are sharing with me and share DNA in some of the same places on the chromosomes. I've marked their shared segments and again have identified many shared matches who match in the same place on the chromosomes.

Relatives in common feature at 23andMe
Below is a screenshot showing a 3rd cousin's stats who isn't open sharing, but is a common match with another match I selected. You can see I've sent them a request to share. Oddly this match shares a higher percentage of DNA, but is described as the selected matches' 4th cousin. The high percentage of DNA that we all share would lead me to believe there is a good likelihood that we are all related through the same ancestors. Below this good match I have a shared 4th cousin match who is described as a distant cousin to the selected match. They share very little DNA and the likelihood we all share the same common ancestors would be less likely. 

In the example below the match I selected is an open sharing match with everyone, as is one of our shared matched.  Below you can see  the stats for our common open sharing match. The "yes" next to this match means we share a DNA segment in the same place, and we can compare in the chromosome browser. This match has no posted information about their ancestors, or surnames.  I have identified common ancestors with the selected match so I can infer this common match shares these same ancestors. 23andMe tells us these shared matches do indeed match each.
Here are the segments they share with me. They overlap and they match each other in the same place.

I have other matches in the same place on chromosome 10 who have the same shared ancestors. I can safely name the region after the shared Roller/Zirkle ancestors, who are the most common recent ancestors, MRCA. When I have matches with segments on chr 10, on my maternal side, I can assume if this is a true match, they must be related through the Roller line.
I have been able to nearly completely fill in chromosome 14 for my mother with segments shared by tree verified matches on her paternal side (her mother was Nicaraguan, and her father Anglo American). I don't share these matches on chr 14 with my mother. Looking at my own segment map I have Nicaragua matches here, not the Anglo American matches my mother has. I didn't inherit DNA from my Grandfather on ch 14. I cannot inherit segments from both of my paternal, or maternal, grandparents in the exact same place on a chromosome.
The 23andMe tools for atDNA are a joy to work with. They greatly aid us in achieving our goal of identifying how we are related to someone in an accurate way. You can't accurately identify how distant cousins are related without a segment map. We can be related to distant cousins through more than one line. A good segment map can find errors in our inferred DNA relationships, and point us to the correct DNA connection. The fact 23andMe shares predicted relationships between common matches also helps us solve relationship puzzles. Many have tested close relatives, we can identify these family group matches when we see their relationship to each other in the common relative lists. They may not share a common surname, but may be parent and child , or uncle and niece or nephew. Percentages of DNA shared are also helpful in determining how, or if, common relatives are likely related through the same ancestors. I wish all of the DNA testing companies had these outstanding features.


1 comment:

Magda said...

I agree with you 100%. I have been using FTDNA for awhile but nothing beats that triangulation tool at 23 ! I always recommend it to anyone who does not want to do spreadsheets for segments.