Visualising DNA matches–FTDNA data

I decided to see what I could learn from my Family Tree DNA (FTDNA) match data when I looked at it using the visualisation tool, NodeXL. For my earlier discussion of this tool, see my post where I investigate Ancestry DNA data with it.

I match with around 960 individuals in FTDNA. There are around 10,000 ‘in common with’ matches between those people. Lets see how 10,000 connections between 960 people looks….

Like a colony of spiders, perhaps?

Each dot represents a person, each line represent a DNA connection between two individuals. There are two bunched up areas of dots where my matches have a lot of interconnections, but otherwise there is little structure to be seen. I tried using all the different layout algorithms available, but this is as good as it gets on the first pass.

Since my father has tested I can divide my DNA matches into two groups based on whether they also match him. I have called the two groups “Paternal” and “Maternal” – which possibly is not entirely accurate but will be close enough for my purposes here – and redrawn the chart with each group laid out separately.

There are clearly a lot of interconnection between my maternal and paternal matches. I’m surprised by the number of the interconnections, as I don’t descend from an endogamous population.

There are two critical facts about the ‘in common with’ relationships that are not shown in the chart:

• how close the relationship between my DNA matches is, and more importantly
• whether their relationships are anything to do with my family tree.

It may be possible to incorporate the second point using FTDNA data. It should be possible to incorporate both points using GEDMatch. I hope to attempt this in a future post.

This exercise suggests to me that it would be even more dangerous than I thought to rely on on ‘in common with’ data without also inspecting segment data.

Ancestry DNA is coming to Australia soon

Today I received an email from Ancestry.com.au that said they will soon be making their DNA tests available in Australia. Tests will initially be available by invitation only. The email gave the option to sign up for an invitation.

I am cautiously optimistic about this development. While I prefer to use Family Tree DNA for my own tests, and of course hope that my relatives near and far will choose to test there, I think that Ancestry will give genetic genealogy in Australia a real boost.

I have tested with all three of the big genetic genealogy players – Family Tree DNA, Ancestry and 23andMe. I tested with Ancestry when the product became available in the USA. At that stage, they shipped kits to Australia.

My hope is that Ancestry’s advertising will ‘normalise’ genetic genealogy. I think that is already starting to happen, but my perspective may be biased by the company I keep! I hope that by seeing a well known company such as Ancestry advertise their tests, more Australian genealogists (and their family members) will think of DNA testing as something that would be interesting to do and within reach of normal people. More potential matches for me!

The chief problem with testing at Ancestry is the sad lack of tools offered to work with matches. Two words... Chromosome browser. Tests done at Ancestry are not a lost cause, though, if you want to work with the information. It’s possible to download the raw data and upload it to free sites such as Gedmatch, or pay a small ‘transfer’ fee to load it into Family Tree DNA.

I think that it’s probably a larger leap to start DNA testing at all, than to expand your view to the additional services available. I will suggest to my promising Australian future AncestryDNA matches that they look a little wider.

More DNA tests mean more information (part 2)

In my last post, I looked at how I could use the “matches in common” lists on Family Tree DNA to pencil in which branch my DNA matches (probably) belong to.

With the addition of my father’s and two cousins’ match-in-common lists, I was able to label each of my matches as connected to my:

• maternal side,
• paternal side, or
• a specific branch on my paternal side, “French”.

Up to this point, all that I have used is the lists of names. My next step is to start looking at the chromosome browser results. This is where you can see what segment(s) of DNA you have in common with each of your matches.

What I intend to do is much like the logic I have discussed before, only this time I want to take it a few steps further.

Matches-not-in-common with a known cousin

The key point to remember here is that for each stretch of DNA, half is from my mother’s side, half is from my father’s. If I match person “A” and person “B” at a particular location, but they don’t match each other, then I know that one is from my maternal and one is from my paternal side. Without additional information, I don’t know which! I now have that additional information for my own DNA matches, as I can see if my father (who happens to have contributed half of my DNA) matches.

For my father’s matches, I can look at his matches not-in-common with our “French” cousins to do something similar. If my father matches a “French” cousin at a particular location then anyone who matches him at the same location, but is NOT a match in common with my “French” cousins (who are on my father’s paternal side), must somehow connect to his maternal side, the “Bennett” branch.

Then it gets weird

So far so good. I started working away at my file on this basis and quickly found a match to my father at the same location on his DNA as my “French” cousin matches, who didn’t show as a match to them. Great! This person must match my “Bennett” family! Then I noticed that I had another match with the same surname and same contact email address on the same segment of DNA, who also did not match my French cousins.

No problem there? Well actually, there was a little problem. When I said “I” had a match I really meant “I” and not my father. My father’s matches not-in-common with my “French” cousins must connect to his “Bennett” branch. My matches not-in-common with my “French” cousins must connect to my mother’s side. Any yet – the two matches had the same surname and contact email address.

I wanted to find out more about these odd matches, so I sent off an email and asked. It turned out that one of our matches was the uncle of the other. My father matched the nephew, I matched the paternal side uncle. So, by using the same sort of logic, my father connects to the maternal side of one match, and I connect to the father’s maternal side of the other. Like a mirror image of how they connect to me. All on the one segment of DNA.

At least, I think that’s how it goes. It took a bit of getting my head around this. Another way of looking at it is this:

But what a funny coincidence that it’s all at exactly the same location on our DNA. It’s even possible that our relationship looks like this:

Ouch! My head hurts!

I think that the moral of this story is that when you pencil in a branch, you really need to pencil it in and keep your mind open to other possibilities.

I think I’ll have to leave it there for tonight…

More DNA tests means more information

I love the puzzling-it-out aspect of genealogy DNA investigation. I’ve now had two known cousins (both on my father’s side) and more recently my father contribute DNA tests. We are using Family Tree DNA. With each additional test comes a big increase in possibilities for narrowing down which part of my family tree is relevant to each of my matches.

I thought it might be of interest to see what I am learning from these tests, despite not yet finding the paper trail to any of my previously unknown matches! I’m very pleased to say though that the results confirm the paper trails to my father and known cousins. A big Phew! there – those relationships are close enough that surprising DNA results would most definitely not be welcome.

When I had only myself tested, this was the extent of my knowledge about my 103 matches:

Note: I’m using all my current matches which include my father and cousins throughout this post for illustration purposes.

Not very helpful.

Then, two known cousins tested. I discussed the results of one of those cousin’s tests here. With Family Tree DNA, once a known relationship is confirmed by both parties you are able to see which of your matches you have in common with that person. As I am not controlling their accounts, I don’t have access to my cousins’ match lists, just to who we have in common. Both of my known cousins are connected to my French branch but their “matches in common” with me didn’t overlap with each other. In total, I was able to pencil in ten of my matches as somehow connected to my French branch. My cousins are actually half-cousins, so it narrowed down the possibilities to just one eighth of my tree for those ten people.  

This is the state of my knowledge after my cousins tested:

At new year my Dad agreed to testing. That was very much to my surprise as he had previously turned up his nose at all attempts to discuss it. His test results came back just a few days ago, and what a lot of extra information they provide!

• by comparing his results with my cousins I see that 10 matches are connected to my French family (no change here yet, but this number may increase when both my cousins have confirmed their relationships with my Dad)
• as well as those ten, 28 more of my matches are somewhere on my father’s side of the tree
• my remaining 65 matches must be from my mother’s side of the tree
• PLUS I have names for 48 new matches on my father’s side of the tree.

This is what the state of my knowledge looks like now:

So far I have only looked at name lists, but even that gives a great starting point for when I compare notes with my matches. I am thinking through the steps to run this sort of analysis in an automated way so I can update it easily as new results come in.

I think it really shows that it’s the more the merrier, so far as DNA testing is concerned! I wonder who else would be willing to part with a bit of spit…

This is just step one. There is a whole lot more narrowing down that will be possible once I start looking at the data on the matches themselves (ie, the location of the match on my DNA) but this post is quite long enough for one night.

Analysis of a second cousin DNA match

Recently, one of my known cousins took a DNA test with Family Tree DNA. He’s a half second cousin to me. We have a great-grandfather in common but descend from different wives. I’ve been looking forward to seeing the results and figuring out what they reveal.

Direct comparison

The DNA test came back as a match, showing us as predicted second cousins with a range of second to third cousins. Spot on. We have a total of 141 cM in common over 20 segments of shared DNA, with the longest block being 33 cM.

Here is FTDNA’s representation of where my known cousin and I are half identical (only half due to the other half of our DNA coming from the other parent). Our shared segments of DNA are marked in yellowy-orange. Only segments of at least 5 cM are shown in this view.

This tells me that half of those yellowy-orange areas of my DNA came to me from our shared great-grandfather.

I think that’s a pretty cool thing to know.

Matches in common

My cousin has confirmed our relationship as second cousins in Family Tree DNA, and I can now see who we match common. I have 63 matches in total on Family Tree DNA, three of whom also match my known cousin.

I can add our matches in common to the comparison. One match shares a segment of DNA in common with both myself and my known cousin. The other two must obviously match my known cousin elsewhere, and I assume that they match each other at the location shown, although it’s possible they don’t. I think it would be reasonable to pencil that location of my DNA in as (half) coming from my great-grandfather.

 

Our three matches in common are unfortunately predicted to be fairly distant cousins so I’m not optimistic that we will work out our connection. I do hope to contact each of them before too long and tell them which branch of my tree our common ancestor falls in, though. Perhaps I will be proved wrong. That would be good!

Matches not in common

Finally I looked at anyone who matched at the same location as my known cousin, but wasn’t a match in common with him.

Unfortunately the relevant segments for the people who met these conditions were quite small. I can’t draw the conclusion I had hoped to – that my common ancestor with these people is on my mother’s side. Because the segments are only small, they may be related to my known cousin but not meet FTDNA’s threshold for declaring someone a match.

Here’s an example of a comparison of my known cousin with another of my matches (who doesn’t match him) that almost shows what I was hoping to find. This time segments of 3cM and larger are showing, as this match didn’t share any segments of 5cM or more with my known cousin:

All in all, I think this new information has given me a few edge pieces of the DNA jigsaw puzzle.

Is there anything else I could have drawn from this or should have considered?

FamilyTreeDNA results – Population Finder

Yesterday, a week ahead of schedule, my FamilyTreeDNA Family Finder results came back. I’ve also had testing with 23andMe as well (see my earlier posts covering health and haplogroups and Ancestry Finder) and have been looking forward to comparing the two.

The FamilyTreeDNA pages don’t give much away about what you will actually see when your results come back. Although I had some idea of the most important content – a list of matches with names attached! – the detail of what would be returned wasn’t 100% clear to me even after searching the FAQs.  Now I see a new set of menu items in the side bar.

When I discussed the 23andMe results I covered the health and haplogroup information first. FamilyTreeDNA doesn’t provide health information, and haplogroups require a different test. What I do have is a tool that compares my DNA against various reference populations.

Population Finder

The FamilyTreeDNA Population Finder goes to a greater level of detail than any of the similar tools in 23andMe. 23andMe had me as 100% European – a boringly expected result! Population Finder went further. It has me as 100% Orcadian, by which I gather they mean British Isles. The confidence interval was plus or minus 0.01% - they couldn’t really get much more confident about what part of the world my genes appear to have come from.

The thing that surprised me about this was that even with many more subgroups (see here) they didn’t see even a smidgeon of me that looked like somewhere other than British Isles! That’s so boring that it’s interesting again.

Next time – Matches