Concepts: Chromosome Browser – What Is It, How Do I Use It, and Why Do I Care?

The goal of genetic genealogy is to utilize DNA matches to verify known ancestors and identify unknown ancestors.

A chromosome browser is a tool that allows testers to visualize and compare their DNA on each chromosome with that of their genetic matches. How to utilize and interpret that information becomes a little more tricky.

I’ve had requests for one article with all the information in one place about chromosome browsers:

  • What they are
  • How and when to use them
  • Why you’d want to

I’ve included a feature comparison chart and educational resource list at the end.

I would suggest just reading through this article the first time, then following along with your own DNA results after you understand the basic landscape. Using your own results is the best way to learn anything.

What Does a Chromosome Browser Look Like?

Here’s an example of a match to my DNA at FamilyTreeDNA viewed on their chromosome browser.

browser example.png

On my first 16 chromosomes, shown above, my 1C1R (first cousin once removed,) Cheryl, matches me where the chromosomes are painted blue. My chromosome is represented by the grey background, and her matching portion by the blue overlay.

Cheryl matches me on some portion of all chromosomes except 2, 6, and 13, where we don’t match at all.

You can select any one person, like Cheryl, from your match list to view on a chromosome browser to see where they match you on your chromosomes, or you can choose multiple matches, as shown below.

browser multiple example.png

I selected my 7 closest matches that are not my immediate family, meaning not my parents or children. I’m the background grey chromosome, and each person’s match is painted on top of “my chromosome” in the location where they match me. You see 7 images of my grey chromosome 1, for example, because each of the 7 people being compared to me are shown stacked below one another.

Everyplace that Cheryl matches me is shown on the top image of each chromosome, and our matching segment is shown in blue. The same for the second red copy of the chromosome, representing Don’s match to me. Each person I’ve selected to match against is shown by their own respective color.

You’ll note that in some cases, two people match me in the same location. Those are the essential hints we are looking for. We’ll be discussing how to unravel, interpret, and use matches in the rest of this article.

browser MyHeritage example.png

The chromosome browser at MyHeritage looks quite similar. However, I have a different “top 7” matches because each vendor has people who test on their platform who don’t test or transfer elsewhere.

Each vendor that supports chromosome browsers (FamilyTreeDNA, MyHeritage, 23andMe, and GedMatch) provides their own implementation, of course, but the fundamentals of chromosome browsers, how they work and what they are telling us is universal.

Why Do I Need a Chromosome Browser?

“But,” you might say, “I don’t need to compare my DNA with my matches because the vendors already tell me that I match someone, which confirms that we are related and share a common ancestor.”

Well, not exactly. It’s not quite that straightforward.

Let’s take a look at:

  • How and why people match
  • What matches do and don’t tell you
  • Both with and without a chromosome browser

In part, whether you utilize a chromosome browser or not depends on which of the following you seek:

  • A broad-brush general answer; yes or no, I match someone, but either I don’t know how are related, or have to assume why. There’s that assume word again.
  • To actually confirm and prove your ancestry, getting every ounce of value out of your DNA test.

Not everyone’s goals are the same. Fortunately, we have an entire toolbox with a wide range of tools. Different tools are better suited for different tasks.

People seeking unknown parents should read the article, Identifying Unknown Parents and Individuals Using DNA Matching because the methodology for identifying unknown parents is somewhat different than working with genealogy. This article focuses on genealogy, although the foundation genetic principles are the same.

If you’re just opening your DNA results for the first time, the article, First Steps When Your DNA Results are Ready – Sticking Your Toe in the Genealogy Water would be a great place to start.

Before we discuss chromosome browsers further, we need to talk about DNA inheritance.

Your Parents

Every person has 2 copies of each of their 22 chromosomes – one copy contributed by their mother and one copy contributed by their father. A child receives exactly half of the autosomal DNA of each parent. The DNA of each parent combines somewhat randomly so that you receive one chromosome’s worth of DNA from each of your parents, which is half of each parent’s total.

On each chromosome, you receive some portion of the DNA that each parent received from their ancestors, but not exactly half of the DNA from each individual ancestor. In other words, it’s not sliced precisely in half, but served up in chunks called segments.

Sometimes you receive an entire segment of an ancestor’s DNA, sometimes none, and sometimes a portion that isn’t equal to half of your parent’s segment.

browser inheritance.png

This means that you don’t receive exactly half of the DNA of each of your grandparents, which would be 25% each. You might receive more like 22% from one maternal grandparent and 28% from the other maternal grandparent for a total of 50% of the DNA you inherit from your parents. The other 50% of your DNA comes from the other parent, of course. I wrote about that here.

There’s one tiny confounding detail. The DNA of your Mom and Dad is scrambled in you, meaning that the lab can’t discern scientifically which side is which and can’t tell which pieces of DNA came from Mom and which from Dad. Think of a genetic blender.

Our job, using genetic genealogy, is to figure out which side of our family people who match us descend from – which leads us to our common ancestor(s).

Parallel Roads

For the purposes of this discussion, you’ll need to understand that the two copies you receive of each chromosome, one from each parent, have the exact same “addresses.” Think of these as parallel streets or roads with identical addresses on each road.

browser street.png

In the example above, you can see Dad’s blue chromosome and Mom’s red chromosome as compared to me. Of course, children and parents match on the full length of each chromosome.

I’ve divided this chromosome into 6 blocks, for purposes of illustration, plus the centromere where we generally find no addresses used for genetic genealogy.

In the 500 block, we see that the address of 510 Main (red bar) could occur on either Dad’s chromosome, or Mom’s. With only an address and nothing more, you have no way to know whether your match with someone at 510 Main is on Mom’s or Dad’s side, because both streets have exactly the same addresses.

Therefore, if two people match you, at the same address on that chromosome, like 510 Main Street, they could be:

  • Both maternal matches, meaning both descended from your mother’s ancestors, and those two people will also match each other
  • Both paternal matches, meaning both descended from your father’s ancestors, and those two people will also match each other
  • One maternal and one paternal match, and those two people will not match each other

Well then, how do we know which side of the family a match descends from, and how do we know if we share a common ancestor?

Good question!

Identical by Descent

If you and another person match on a reasonably sized DNA segment, generally about 7 cM or above, your match is probably “identical by descent,” meaning not “identical by chance.” In this case, then yes, a match does confirm that you share a common ancestor.

Identical by descent (IBD) means you inherited the piece of DNA from a common ancestor, inherited through the relevant parent.

Identical by chance (IBC) means that your mom’s and dad’s DNA just happens to have been inherited by you randomly in a way that creates a sequence of DNA that matches that other person. I wrote about both IBD and IBC here.

MMB stats by cM 2

This chart, courtesy of statistician Philip Gammon, from the article Introducing the Match-Maker-Breaker Tool for Parental Phasing shows the percentage of time we expect matches of specific segment sizes to be valid, or identical by descent.

Identical by Chance

How does this work?

How is a match NOT identical by descent, meaning that it is identical by chance and therefore not a “real” or valid match, a situation also known as a false positive?

browser inheritance grid.png

The answer involves how DNA is inherited.

You receive a chromosome with a piece of DNA at every address from both parents. Of course, this means you have two pieces of DNA at each address. Therefore people will match you on either piece of DNA. People from your Dad’s side will match you on the pieces you inherited from him, and people from your Mom’s side will match you on the pieces you inherited from her.

However, both of those matches have the same address on their parallel streets as shown in the illustration, above. Your matches from your mom’s side will have all As, and those from your dad’s side will have all Ts.

The problem is that you have no way to know which pieces you inherited from Mom and from Dad – at least not without additional information.

You can see that for 10 contiguous locations (addresses), which create an example “segment” of your DNA, you inherited all As from your Mom and all Ts from your Dad. In order to match you, someone would either need to have an A or a T in one of their two inherited locations, because you have an A and a T, both. If the other person has a C or a G, there’s no match.

Your match inherited a specific sequence from their mother and father, just like you did. As you can see, even though they do match you because they have either an A or a T in all 10 locations – the As and Ts did not all descend from either their mother or father. Their random inheritance of Ts and As just happens to match you.

If your match’s parents have tested, you won’t match either of their parents nor will they match either of your parents, which tells you immediately that this match is by chance (IBC) and not by descent (IBD), meaning this segment did not come from a common ancestor. It’s identical by chance and, therefore, a false positive.

If We Match Someone Else In Common, Doesn’t That Prove Identical by Descent?

Nope, but I sure wish it did!

The vendors show you who else you and your match both match in common, which provides a SUGGESTION as to your common ancestor – assuming you know which common ancestor any of these people share with you.

browser icw.png

However, shared matches are absolutely NOT a guarantee that you, your match, and your common matches all share the same ancestor, unless you’re close family. Your shared match could match you or your match through different ancestors – or could be identical by chance.

How can we be more confident of what matching is actually telling us?

How can we sort this out?

Uncertainties and Remedies

Here’s are 9 things you DON’T know, based on matching alone, along with tips and techniques to learn more.

  1. If your match to Person A is below about 20cM, you’ll need to verify that it’s a legitimate IBD match (not IBC). You can achieve this by determining if Person A also matches one of your parents and if you match one of Person A’s parents, if parents have tested.

Not enough parents have tested? An alternative method is by determining if you and Person A both match known descendants of the candidate ancestors ON THE SAME SEGMENT. This is where the chromosome browser enters the picture.

In other words, at least three people who are confirmed to descend from your presumptive common ancestor, preferably through at least two different children, must match on a significant portion of the same segment.

Why is that? Because every segment has its own unique genealogical history. Each segment can and often does lead to different ancestors as you move further back in time.

In this example, I’m viewing Buster, David, and E., three cousins descended from the same ancestral couple, compared to me on my chromosome browser. I’m the background grey, and they show in color. You can see that all three of them match me on at least some significant portion of the same segment of chromosome 15.

browser 3 cousins.png

If those people also match each other, that’s called triangulation. Triangulation confirms descent from a common ancestral source.

In this case, I already know that these people are related on my paternal side. The fact that they all match my father’s DNA and are therefore all automatically assigned to my paternal matching tab at Family Tree DNA confirms my paper-trail genealogy.

I wrote detailed steps for triangulation at Family Tree DNA, here. In a nutshell, matching on the same segment to people who are bucketed to the same parent is an automated method of triangulation.

Of course, not everyone has the luxury of having their parents tested, so testing other family members, finding common segments, and assigning people to their proper location in your tree facilitates confirmation of your genealogy (and automating triangulation.)

The ONLY way you can determine if people match you on the same segment, and match each other, is having segment information available to you and utilizing a chromosome browser.

browser MyHeritage triangulation.png

In the example above, the MyHeritage triangulation tool brackets matches that match you (the background grey) and who are all triangulated, meaning they all also match each other. In this case, the portion where all three people match me AND each other is bracketed. I wrote about triangulation at MyHeritage here.

  1. If you match several people who descend from the same ancestor, John Doe, for example, on paper, you CANNOT presume that your match to all of those people is due to a segment of DNA descended from John Doe or his wife. You may not match any of those people BECAUSE OF or through segments inherited from John Doe or his wife. You need segment information and a chromosome browser to view the location of those matches.

Assuming these are legitimate IBD matches, you may share another common line, known or unknown, with some or all of those matches.

It’s easy to assume that because you match and share matches in common with other people who believe they are descended from that same ancestor:

  • That you’re all matching because of that ancestor.
  • Even on the same segments.

Neither of those presumptions can be made without additional information.

Trust me, you’ll get yourself in a heap o’ trouble if you assume. Been there, done that. T-shirt was ugly.

Let’s look at how this works.

browser venn.png

Here’s a Venn diagram showing me, in the middle, surrounded by three of my matches:

  • Match 1 – Periwinkle, descends from Lazarus Estes and Elizabeth Vannoy
  • Match 2 – Teal, descends from Joseph Bolton and Margaret Claxton
  • Match 3 – Mustard, descends from John Y. Estes and Rutha Dodson

Utilizing a chromosome browser, autocluster software, and other tools, we can determine if those matches also match each other on a common segment, which means they triangulate and confirm common ancestral descent.

Of course, those people could match each other due to a different ancestor, not necessarily the one I share with them nor the ancestors I think we match through.

If they/we do all match because they descend from a common ancestor, they can still match each other on different segments that don’t match me.

I’m in the center. All three people match me, and they also match each other, shown in the overlap intersections.

Note that the intersection between the periwinkle (Match 1) and teal (Match 2) people, who match each other, is due to the wives of the children of two of my ancestors. In other words, their match to each other has absolutely nothing to do with their match to me. This was an “aha’ moment for me when I first realized this was a possibility and happens far more than I ever suspected.

The intersection of the periwinkle (Match 1) and mustard (Match 3) matches is due to the Dodson line, but on a different segment than they both share with me. If they had matched each other and me on the same segment, we would be all triangulated, but we aren’t.

The source of the teal (Match 2) to mustard (Match 3) is unknown, but then again, Match 3’s tree is relatively incomplete.

Let’s take a look at autocluster software which assists greatly with automating the process of determining who matches each other, in addition to who matches you.

  1. Clustering technology, meaning the Leeds method as automated by Genetic Affairs and DNAGedcom help, but don’t, by themselves, resolve the quandary of HOW people match you and each other.

People in a colored cluster all match you and each other – but not necessarily on the same segment, AND, they can match each other because they are related through different ancestors not related to your ancestor. The benefit of autocluster software is that this process is automated. However, not all of your matches will qualify to be placed in clusters.

browser autocluster.png

My mustard cluster above includes the three people shown in the chromosome browser examples – and 12 more matches that can be now be researched because we know that they are all part of a group of people who all match me, and several of whom match each other too.

My matches may not match each other for a variety of reasons, including:

  • They are too far removed in time/generations and didn’t inherit any common ancestral DNA.
  • This cluster is comprised of some people matching me on different (perhaps intermarried) lines.
  • Some may be IBC matches.

Darker grey boxes indicate that those people should be in both clusters, meaning the red and mustard clusters, because they match people in two clusters. That’s another hint. Because of the grid nature of clusters, one person cannot be associated with more than 2 clusters, maximum. Therefore, people like first cousins who are closely related to the tester and could potentially be in many clusters are not as useful in clusters as they are when utilizing other tools.

  1. Clusters and chromosome browsers are much less complex than pedigree charts, especially when dealing with many people. I charted out the relationships of the three example matches from the Venn diagram. You can see that this gets messy quickly, and it’s much more challenging to visualize and understand than either the chromosome browser or autoclusters.

Having said that, the ultimate GOAL is to identify how each person is related to you and place them in their proper place in your tree. This, cumulatively with your matches, is what identifies and confirms ancestors – the overarching purpose of genealogy and genetic genealogy.

Let’s take a look at this particular colorized pedigree chart.

Browser pedigree.png

click to enlarge

The pedigree chart above shows the genetic relationship between me and the three matches shown in the Venn diagram.

Four descendants of 2 ancestral couples are shown, above; Joseph Bolton and Margaret Claxton, and John Y. Estes and Rutha Dodson. DNA tells me that all 3 people match me and also match each other.

The color of the square (above) is the color of DNA that represents the DNA segment that I received and match with these particular testers. This chart is NOT illustrating how much DNA is passed in each generation – we already know that every child inherits half of the DNA of each parent. This chart shows match/inheritance coloring for ONE MATCHING SEGMENT with each match, ONLY.

Let’s look at Joseph Bolton (blue) and Margaret Claxton (pink). I descend through their daughter, Ollie Bolton, who married William George Estes, my grandfather. The DNA segment that I share with blue Match 2 (bottom left) is a segment that I inherited from Joseph Bolton (blue). I also carry inherited DNA from Margaret Claxton too, but that’s not the segment that I share with Match 2, which is why the path from Joseph Bolton to me, in this case, is blue – and why Match 2 is blue. (Just so you are aware, I know this segment descends from Joseph Bolton, because I also match descendants of Joseph’s father on this segment – but that generation/mtach is not shown on this pedigree chart.)

If I were comparing to someone else who I match through Margaret Claxton, I would color the DNA from Margaret Claxton to me pink in that illustration. You don’t have to DO this with your pedigree chart, so don’t worry. I created this example to help you understand.

The colored dots shown on the squares indicate that various ancestors and living people do indeed carry DNA from specific ancestors, even though that’s not the segment that matches a particular person. In other words, the daughter, Ollie, of Joseph Bolton and Margaret Claxton carries 50% pink DNA, represented by the pink dot on blue Ollie Bolton, married to purple William George Estes.

Ollie Bolton and William George Estes had my father, who I’ve shown as half purple (Estes) and half blue (Bolton) because I share Bolton DNA with Match 2, and Estes DNA with Match 1. Obviously, everyone receives half of each parent’s DNA, but in this case, I’m showing the path DNA descended for a specific segment shared with a particular match.

I’ve represented myself with the 5 colors of DNA that I carry from these particular ancestors shown on the pedigree chart. I assuredly will match other people with DNA that we’ve both inherited from these ancestors. I may match these same matches shown with DNA that we both inherited from other ancestors – for example, I might match Match 2 on a different segment that we both inherited from Margaret Claxton. Match 2 is my second cousin, so it’s quite likely that we do indeed share multiple segments of DNA.

Looking at Match 3, who knows very little about their genealogy, I can tell, based on other matches, that we share Dodson DNA inherited through Rutha Dodson.

I need to check every person in my cluster, and that I share DNA with on these same segment addresses to see if they match on my paternal side and if they match each other.

  1. At Family Tree DNA, I will be able to garner more information about whether or not my matches match each other by using the Matrix tool as well as by utilizing Phased Family Matching.

At Family Tree DNA, I determined that these people all match in common with me and Match 1 by using the “In Common With” tool. You can read more about how to use “In Common With” matching, here.

browser paternal.png

Family Matching phases the matches, assigning or bucketed them maternally or paternally (blue and red icons above), indicating, when possible, if these matches occur on the same side of your family. I wrote about the concept of phasing, here, and Phased Family Matching here and here.

Please note that there is no longer a limit on how distantly related a match can be in order to be utilized in Phased Family Matching, so long as it’s over the phase-matching threshold and connected correctly in your tree.

browser family tree dna link tree.png

Bottom line, if you can figure out how you’re related to someone, just add them into your tree by creating a profile card and link their DNA match to them by simply dragging and dropping, as illustrated above.

Linking your matches allows Family Matching to maternally or paternally assign other matches that match both you and your tree-linked matches.

If your matches match you on the same segment on the same parental side, that’s segment triangulation, assuming the matches are IBD. Phased Family Matching does this automatically for you, where possible, based on who you have linked in your tree.

For matches that aren’t automatically bucketed, there’s another tool, the Matrix.

browser matrix.png

In situations where your matches aren’t “bucketed” either maternally or paternally, the Matrix tool allows you to select matches to determine whether your matches also match each other. It’s another way of clustering where you can select specific people to compare. Note that because they also match each other (blue square) does NOT mean it’s on the same segment(s) where they match you. Remember our Venn diagram.

browser matrix grid.png

  1. Just because you and your matches all match each other doesn’t mean that they are matching each other because of the same ancestor. In other words, your matches may match each other due to another or unknown ancestor. In our pedigree example, you can see that the three matches match each other in various ways.
browser pedigree match.png

click to enlarge

  • Match 1 and Match 2 match each other because they are related through the green Jones family, who is not related to me.
  • Match 2 and Match 3 don’t know why they match. They both match me, but not on the same segment they share with each other.
  • Match 1 and Match 3 match through the mustard Dodson line, but not on the same segment that matches me. If we all did match on the same segment, we would be triangulated, but we wouldn’t know why Match 3 was in this triangulation group.
  1. Looking at a downloaded segment file of your matches, available at all testing vendors who support segment information and a chromosome browser, you can’t determine without additional information whether your matches also match each other.

browser chr 15.png

Here’s a group of people, above, that we’ve been working with on chromosome 15.

My entire match-list shows many more matches on that segment of chromosome 15. Below are just a few.

browser chr 15 all

Looking at seven of these people in the chromosome browser, we can see visually that they all overlap on part of a segment on chromosome 15. It’s a lot easier to see the amount of overlap using a browser as opposed to the list. But you can only view 7 at a time in the browser, so the combination of both tools is quite useful. The downloaded spreadsheet shows you who to select to view for any particular segment.

browser chr 15 compare.png

The critical thing to remember is that some matches will be from tyour mother’s side and some from your father’s side.

Without additional information and advanced tools, there’s no way to tell the difference – unless they are bucketed using Phased Family Matching at Family Tree DNA or bracketed with a triangulation bracket at MyHeritage.

At MyHeritage, this assumes you know the shared ancestor of at least one person in the triangulation group which effectively assigns the match to the maternal or paternal side.

Looking at known relatives on either side, and seeing who they also match, is how to determine whether these people match paternally or maternally. In this example below, the blue people are bucketed paternally through Phased Family Matching, the pink maternally, and the white rows aren’t bucketed and therefore require additional evaluation.

browser chr 15 maternal paternal.png

Additional research shows that Jonathan is a maternal match, but Robert and Adam are identical by chance because they don’t match either of my parents on this segment. They might be valid matches on other segments, but not this one.

browser chr 15 compare maternal paternal.png

  1. Utilizing relatives who have tested is a huge benefit, and why we suggest that everyone test their closest upstream relatives (meaning not children or grandchildren.) Testing all siblings is recommended if both parents aren’t available to test, because every child received different parts of their parents’ DNA, so they will match different relatives.

After deleting segments under 7 cM, I combine the segment match download files of multiple family members (who agree to allow me to aggregate their matches into one file for analysis) so that I can create a master match file for a particular family group. Sorting by match name, I can identify people that several of my cousins’ match.

browser 4 groups.png

This example is from a spreadsheet where I’ve combined the results of about 10 collaborating cousins to determine if we can break through a collective brick wall. Sorted by match name, this table shows the first 4 common matches that appear on multiple cousin’s match lists. Remember that how these people match may have nothing to do with our brick wall – or it might.

Note that while the 4 matches, AB, AG, ag, and A. Wayne, appear in different cousins’ match lists, only one shares a common segment of DNA: AB triangulates with Buster and Iona. This is precisely WHY you need segment information, and a chromosome browser, to visualize these matches, and to confirm that they do share a common DNA segment descended from a specific ancestor.

These same people will probably appear in autocluster groups together as well. It’s worth noting, as illustrated in the download example, that it’s much more typical for “in common with” matches to match on different segments than on the same segment. 

  1. Keep in mind that you will match both your mother and father on every single chromosome for the entire length of each chromosome.

browser parent matching.png

Here’s my kit matching with my father, in blue, and mother, in red on chromosomes 1 and 2.

Given that I match both of my parents on the full chromosome, inheriting one copy of my chromosome from each parent, it’s impossible to tell by adding any person at random to the chromosome browser whether they match me maternally or paternally. Furthermore, many people aren’t fortunate enough to have parents available for testing.

To overcome that obstacle, you can compare to known or close relatives. In fact, your close relatives are genetic genealogy gold and serve as your match anchor. A match that matches you and your close relatives can be assigned either maternally or paternally. I wrote about that here.

browser parent plus buster.png

You can see that my cousin Buster matches me on chromosome 15, as do both of my parents, of course. At this point, I can’t tell from this information alone whether Buster matches on my mother’s or father’s side.

I can tell you that indeed, Buster does match my father on this same segment, but what if I don’t have the benefit of my father’s DNA test?

Genealogy tells me that Buster matches me on my paternal side, through Lazarus Estes and Elizabeth Vannoy. Given that Buster is a relatively close family member, I already know how Buster and I are related and that our DNA matches. That knowledge will help me identify and place other relatives in my tree who match us both on the same segment of DNA.

To trigger Phased Family Matching, I placed Buster in the proper place in my tree at Family Tree DNA and linked his DNA. His Y DNA also matches the Estes males, so no adoptions or misattributed parental events have occurred in the direct Estes patrilineal line.

browser family tree dna tree.png

I can confirm this relationship by checking to see if Buster matches known relatives on my father’s side of the family, including my father using the “in common with” tool.

Buster matches my father as well as several other known family members on that side of the family on the same segments of DNA.

browser paternal bucket.png

Note that I have a total of 397 matches in common with Buster, 140 of which have been paternally bucketed, 4 of which are both (my children and grandchildren), and 7 of which are maternal.

Those maternal matches represent an issue. It’s possible that those people are either identical by chance or that we share both a maternal and paternal ancestor. All 7 are relatively low matches, with longest blocks from 9 to 14 cM.

Clearly, with a total of 397 shared matches with Buster, not everyone that I match in common with Buster is assigned to a bucket. In fact, 246 are not. I will need to take a look at this group of people and evaluate them individually, their genealogy, clusters, the matrix, and through the chromosome browser to confirm individual matching segments.

There is no single perfect tool.

Every Segment Tells a Unique History

I need to check each of the 14 segments that I match with Buster because each segment has its own inheritance path and may well track back to different ancestors.

browser buster segments.png

It’s also possible that we have unknown common ancestors due to either adoptions, NPEs, or incorrect genealogy, not in the direct Estes patrilineal line, but someplace in our trees.

browser buster paint.png

The best way to investigate the history and genesis of each segment is by painting matching segments at DNAPainter. My matching segments with Buster are shown painted at DNAPainter, above. I wrote about DNAPainter, here.

browser overlap.png

By expanding each segment to show overlapping segments with other matches that I’ve painted and viewing who we match, we can visually see which ancestors that segment descends from and through.

browser dnapainter walk back.png

These roughly 30 individuals all descend from either Lazarus Estes and Elizabeth Vannoy (grey), Elizabeth’s parents (dark blue), or her grandparents (burgundy) on chromosome 15.

As more people match me (and Buster) on this segment, on my father’s side, perhaps we’ll push this segment back further in time to more distant ancestors. Eventually, we may well be able to break through our end-of-line brick wall using these same segments by looking for common upstream ancestors in our matches’ trees.

Arsenal of Tools

This combined arsenal of tools is incredibly exciting, but they all depend on having segment information available and understanding how to use and interpret segment and chromosome browser match information.

One of mine and Buster’s common segments tracks back to end-of-line James Moore, born about 1720, probably in Virginia, and another to Charles Hickerson born about 1724. It’s rewarding and exciting to be able to confirm these DNA segments to specific ancestors. These discoveries may lead to breaking through those brick walls eventually as more people match who share common ancestors with each other that aren’t in my tree.

This is exactly why we need and utilize segment information in a chromosome browser.

We can infer common ancestors from matches, but we can’t confirm segment descent without specific segment information and a chromosome browser. The best we can do, otherwise, is to presume that a preponderance of evidence and numerous matches equates to confirmation. True or not, we can’t push further back in time without knowing who else matches us on those same segments, and the identity of their common ancestors.

The more evidence we can amass for each ancestor and ancestral couple, the better, including:

  • Matches
  • Shared “In Common With” Matches, available at all vendors.
  • Phased Family Matching at Family Tree DNA assigns matches to maternal or paternal sides based on shared, linked DNA from known relatives.
  • The Matrix, a Family Tree DNA tool to determine if matches also match each other. Tester can select who to compare.
  • ThruLines from Ancestry is based on a DNA match and shared ancestors in trees, but no specific segment information or chromosome browser. I wrote about ThruLines here and here.
  • Theories of Family Relativity, aka TOFR, at MyHeritage, based on shared DNA matches, shared ancestors in trees and trees constructed between matches from various genealogical records and sources. MyHeritage includes a chromosome browser and triangulation tool. I wrote about TOFR here and here.
  • Triangulation available through Phased Family Matching at Family Tree DNA and the integrated triangulation tool at MyHeritage. Triangulation between only 3 people at a time is available at 23andMe, although 23andMe does not support trees. See triangulation article links in the Resource Articles section below.
  • AutoClusters at MyHeritage (cluster functionality included), at Genetic Affairs (autoclusters plus tree reconstruction) and at DNAGedcom (including triangulation).
  • Genealogical information. Please upload your trees to every vendor site.
  • Y DNA and mitochondrial DNA confirmation, when available, through Family Tree DNA. I wrote about the 4 Kinds of DNA for Genetic Genealogy, here and the importance of Y DNA confirmation here, and how not having that information can trip you up.
  • Compiled segment information at DNAPainter allows you to combine segment information from various vendors, paint your maternal and paternal chromosomes, and visually walk segments back in time. Article with DNAPainter instructions is found here.

Autosomal Tool Summary Table

In order to help you determine which tool you need to use, and when, I’ve compiled a summary table of the types of tools and when they are most advantageous. Of course, you’ll need to read and understand about each tool in the sections above. This table serves as a reminder checklist to be sure you’ve actually utilized each relevant tool where and how it’s appropriate.

Family Tree DNA MyHeritage Ancestry 23andMe GedMatch
DNA Matches Yes Yes Yes Yes, but only highest 2000 minus whoever does not opt -in Yes, limited matches for free, more with subscription (Tier 1)
Download DNA Segment Match Spreadsheet Yes Yes No, must use DNAGedcom for any download, and no chromosome segment information Yes Tier 1 required, can only download 1000 through visualization options
Segment Spreadsheet Benefits View all matches and sort by segment, target all people who match on specific segments for chromosome browser View all matches and sort by segment, target all people who match on specific segments for chromosome browser No segment information but matches might transfer elsewhere where segment information is available View up to 2000 matches if matches have opted in. If you have initiated contact with a match, they will not drop off match list. Can download highest 1000 matches, target people who match on specific segments
Spreadsheet Challenges Includes small segments, I delete less than 7cM segments before using No X chromosome included No spreadsheet and no segment information Maximum of 2000 matches, minus those not opted in Download limited to 1000 with Tier 1, download not available without subscription
Chromosome Segment Information Yes Yes No, only total and longest segment, no segment address Yes Yes
Chromosome Browser Yes, requires $19 unlock if transfer Yes, requires $29 unlock or subscription if transfer No Yes Yes, some features require Tier 1 subscription
X Chromosome Included Yes No No Yes Yes, separate
Chromosome Browser Benefit Visual view of 7 or fewer matches Visual view of 7 or fewer matches, triangulation included if ALL people match on same portion of common segment No browser Visual view of 5 or fewer matches Unlimited view of matches, multiple options through comparison tools
Chromosome Browser Challenges Can’t tell whether maternal or paternal matches without additional info if don’t select bucketed matches Can’t tell whether maternal or paternal without additional info if don’t triangulate or you don’t know your common ancestor with at least one person in triangulation group No browser Can’t tell whether maternal or paternal without other information Can’t tell whether maternal or paternal without other information
Shared “In Common With” Matches Yes Yes Yes Yes, if everyone opts in Yes
Triangulation Yes, Phased Family Matching, plus chromosome browser Yes, included in chromosome browser if all people being compared match on that segment No, and no browser Yes, but only for 3 people if “Shared DNA” = Yes on Relatives in Common Yes, through multiple comparison tools
Ability to Know if Matches Match Each Other (also see autoclusters) Yes, through Matrix tool or if match on common bucketed segment through Family Matching Yes, through triangulation tool if all match on common segment No Yes, can compare any person to any other person on your match list Yes, through comparison tool selections
Autoclusters Can select up to 10 people for Matrix grid, also available for entire match list through Genetic Affairs and DNAGedcom which work well Genetic Affairs clustering included free, DNAGedcom has difficulty due to timeouts No, but Genetic Affairs and DNAGedcom work well No, but Genetic Affairs and DNAGedcom work well Yes, Genetic Affairs included in Tier 1 for selected kits, DNAGedcom is in beta
Trees Can upload or create tree. Linking you and relatives who match to tree triggers Phased Family Matching Can upload or create tree. Link yourself and kits you manage assists Theories of Family Relativity Can upload or create tree. Link your DNA to your tree to generate ThruLines. Recent new feature allows linking of DNA matches to tree. No tree support but can provide a link to a tree elsewhere Upload your tree so your matches can view
Matching and Automated Tree Construction of DNA Matches who Share Common Ancestors with You Genetic Affairs for matches with common ancestors with you Not available Genetic Affairs for matches with common ancestors with you No tree support Not available
Matching and Automated Tree Construction for DNA Matches with Common Ancestors with Each Other, But Not With You Genetic Affairs for matches with common ancestors with each other, but not with you Not available Genetic Affairs for matches with common ancestors with each other, but not with you No tree support Not available
DNAPainter Segment Compilation and Painting Yes, bucketed Family Match file can be uploaded which benefits tester immensely. Will be able to paint ethnicity segments soon. Yes No segment info available, encourage your matches to upload elsewhere Yes, and can paint ethnicity segments from 23andMe, Yes, but only for individually copied matches or highest 1000.
Y DNA and Mitochondrial Matching Yes, both, includes multiple tools, deep testing and detailed matching No No No, base haplogroup only, no matching No, haplogroup only if field manually completed by tester when uploading autosomal DNA file

Transfer Your DNA

Transferring your DNA results to each vendor who supports segment information and accepts transfers is not only important, it’s also a great way to extend your testing collar. Every vendor has strengths along with people who are found there and in no other database.

Ancestry does not provide segment information nor a chromosome browser, nor accept uploads, but you have several options to transfer your DNA file for free to other vendors who offer tools.

23andMe does provide a chromosome browser but does not accept uploads. You can download your DNA file and transfer free to other vendors.

I wrote detailed upload/download and transfer instructions for each vendor, here.

Two vendors and one third party support transfers into their systems. The transfers include matching. Basic tools are free, but all vendors charge a minimal fee for unlocking advanced tools, which is significantly less expensive than retesting:

Third-party tools that work with your DNA results include:

All vendors provide different tools and have unique strengths. Be sure that your DNA is working as hard as possible for you by fishing in every pond and utilizing third party tools to their highest potential.

Resource Articles

Explanations and step by step explanations of what you will see and what to do, when you open your DNA results for the first time.

Original article about chromosomes having 2 sides and how they affect genetic genealogy.

This article explains what triangulation is for autosomal DNA.

Why some matches may not be valid, and how to tell the difference.

This article explains the difference between a match group, meaning a group of people who match you, and triangulation, where that group also matches each other. The concepts are sound, but this article relies heavily on spreadsheets, before autocluster tools were available.

Parental phasing means assigning segment matches to either your paternal or maternal side.

Updated, introductory article about triangulation, providing the foundation for a series of articles about how to utilize triangulation at each vendor (FamilyTreeDNA, MyHeritage, 23andMe, GEDmatch, DNAPainter) that supports triangulation.

These articles step you through triangulation at each vendor.

DNAPainter facilitates painting maternally and paternally phased, bucketed matches from FamilyTreeDNA, a method of triangulation.

Compiled articles with instructions and ideas for using DNAPainter.

Autoclustering tool instructions.

How and why The Leeds Method works.

Step by step instructions for when and how to use FamilyTreeDNA’s chromosome browser.

Close family members are the key to verifying matches and identifying common ancestors.

This article details how much DNA specific relationships between people can expect to share.

Overview of transfer information and links to instruction articles for each vendor, below.

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Thank you so much.

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Introducing the Match-Maker-Breaker Tool for Parental Phasing

A few days after I published the article, Concepts – Segment Size, Legitimate and False Matches, Philip Gammon, a statistician who lives in Australia, posted a comment to my blog.

Great post Roberta! I’m a statistician so my eyes light up as soon as I see numbers. That table you have produced showing by segment length the percentage that are IBD is one of the most useful pieces of information that I have seen. Two days to do the analysis!!! I’m sure that I could write a formula that would identify the IBD segments and considerably reduce this time.

By this time, my eyes were lighting up too, because the work for the original article had taken me two days to complete manually, just using segments 3 cM and above. Using smaller segments would have taken days longer. By manually, I mean comparing the child’s matches with that of both parents’ matches to see which, if either, parent the child’s match also matches on the same segment.

In the simplest terms, the Segment Size article explained how to copy the child’s and both parents’ matches to a spreadsheet and then manually compare the child’s matches to those of the parents. In the example above, you can see that both the child and the mother have matches to Cecelia. As it turns out, the exact same segment of DNA was passed in its entirety to the child from the mother, who is shown in pink – so Cecelia matches both the child and the parent on exactly the same segment.

That’s not always the case, and the Segment Size article went into much greater detail.

For the past month or so, Philip and I have been working back and forth, along with some kind volunteers who tested Philip’s new tool, in order to create something so that you too can do this comparison and in much less than two days.

Foundation

Here’s the underlying principle for this tool – if a child has a match that does NOT match either parent on the same segment, then the match is not a legitimate match. It’s a false match, identical by chance, and it is NOT genealogically relevant.

If the child’s match also matches either parent on the same segment, it is most likely a match by descent and is genealogically relevant.

For those of you who noticed the words “most likely,” yes, it is possible for someone to match a parent and child both and still not phase (or match) to the next higher generation, but it’s unusual and so far, only found in smaller segments. I wrote about multiple generation phasing in the article, “Concepts – Segment Survival – 3 and 4 Generation Phasing.” Once a segment phases, it tends to continue phasing, especially with segments above about 3.5 cM.

For those who have both parents available to test, phased matching is a HUGE benefit.

But I Have Only One Parent Available

You can still use the tool to identify matches to that one parent, but you CANNOT presume that matches that DON’T match that parent are from the other (missing) parent. Matches matching the child but not matching the tested parent can be due to:

  • A match to the missing parent
  • A false match that is not genealogically relevant

According to the statistics generated from Philip’s Match-Maker-Breaker tool, shown below, segments 9 cM and above tend to match one or the other parent 90% or more of the time.  Segments 12 cM and over match 97% of the time or more, so, in general, one could “assume” (dangerous word, I know) that segments of this size that don’t match to the tested parent would match to the other parent if the other parent was available. You can also see that the reliability of that assumption drops rapidly as the segment sizes get smaller.

Platform

This tool was written utilizing Microsoft Excel and only works reliably on that platform.

If you are using Excel and are NOT attempting to use MAC Numbers, skip this section.  If you want to attempt to use Numbers, read this section.

I tried, along with a MAC person, to try to coax Numbers (free MAC spreadsheet) into working. If you have any other option other than using Numbers, so do. Microsoft Excel for MAC seemed to work fine, but it was only tested on one MAC.

Here’s what I discovered when trying to make Numbers work:

  • You must first launch numbers and then select the various spreadsheets.
  • The tabs are not at the bottom and are instead at the top without color.
  • The instructions for copying the formulas in cells H2-K2 throughout the spreadsheet must be done manually with a copy/paste.
  • After the above step, the calculations literally took a couple hours (MacBook Air) instead of a couple minutes on the PC platform. The older MAC desktop still took significantly longer than on a Microsoft PC, but less time than the solid state MacBook Air.
  • After the calculations complete, the rows on the child’s spreadsheet are not colored, which is one of the major features of the Match-Maker-Breaker tool, as Numbers reports that “Conditional highlighting rules using formulas are not supported and were removed.”
  • Surprisingly, the statistical Reports page seems to function correctly.

How Long Does Running Match-Maker-Breaker Tool on a PC Take?

The first time I ran this tool, which included reading Philip’s instructions for the first time, the entire process took me about 10 minutes after I downloaded the files from Family Tree DNA.

Vendors

This tool only works with matches downloaded from Family Tree DNA.

Transfer Kits

It’s strongly suggested that all 3 individuals being compared have tested at Family Tree DNA or on the same chip version imported into Family Tree DNA.

Matches not run on the same chip as Family Tree DNA testers can only provide a portion of the matches that the same person’s results run on the FTDNA chip can provide. You can run the matching tool with transferred results, but the results will only provide a subset of the results that will be provided by having all parties that are being compared, meaning the child and both parents, test at Family Tree DNA.

The following products versions CAN be all be compared successfully at Family Tree DNA, as they all utilize the same Illumina chip:

  • All Family Finder tests
  • Ancestry V1 (before May 2016)
  • 23andMe V3 (before November 2013)
  • MyHeritage

The following tests do NOT utilize the same Illumina testing platform and cannot be compared successfully with Family Finder tests from Family Tree DNA, or the list above. Cross platform testing results cannot be reliably compared. Those that DO match will be accurate, but many will not match that would match if all 3 testers were utilizing the same platform, therefore leading you to inaccurate conclusions.

  • Ancestry V2 (beginning in May 2016 to present)
  • 23andMe V4 (beginning November 2013 to present)

The child and two parents should not be compared utilizing mixed platforms – meaning, for example, that the child should not have been tested at FTDNA and the parents transferred from Ancestry on the V2 platform since May 2016.

If any of the three family members, being the child or either parent, have tested on an incompatible platform, they should retest at Family Tree DNA before using this tool.

What You Need

  • You will need to download the chromosome match lists from the child and both parents, AT THE SAME TIME. I can’t stress this enough, because any matches that have been added for either of the three people at a later time than the others will skew the matching and the statistics. Matches are being added all the time.
  • You will also need a relatively current version of Excel on your computer to run this tool. No, I did not do version compatibility testing so I don’t know how old is too old. I am running MSOffice 2013.
  • You will need to know how to copy and paste data from and to a spreadsheet.

Instructions for Downloading Match Files

My recommendation is that you download your matches just before utilizing this tool.

To download your matches, sign on to each account. On your main page, you will see the Family Finder section, and the Chromosome Browser. Click on that link.

At the top of the chromosome browser page, below, you’ll see the image of chromosomes 1 through X. At the top right, you’ll see the option to “Download all matches to Excel (CSV Format). Click on that link.

Next, you’ll receive a prompt to open or save the file. Save it to a file name that includes the name of the person plus the date you did the download. I created a separate folder so there would be no confusion about which files are which and whether or not they are current.

Your match file includes all of your matches and the chromosome matching locations like the example shown below.

These files of matches are what you’ll need to copy into the Match-Maker-Breaker spreadsheet.

Do not delete any information from your match spreadsheets. If you normally delete small segments, don’t. You may cause a non-match situation if the parent carries a larger portion of the same segment.

You can rerun the Match-Maker-Breaker tool at will, and it only takes a very few minutes.

The Match-Maker-Breaker Tool

The Match-Maker-Breaker Tool has 5 sheets when you open the spreadsheet:

  • Instructions – Please read entirely before beginning.
  • Results – The page where your statistical results will be placed.
  • Child – The page where you will paste the child’s matches and then look at the match results after processing.
  • Father – The page where you will paste the father’s matches.
  • Mother – The page where you will paste the mother’s matches.

Download

Download the free Match-Maker-Breaker tool which is a spreadsheet by clicking on this link: Match-Maker-Breaker Tool V2

Please don’t start using the tool before reading the instructions completely and reading the rest of this article.

Make a Copy

After you download the tool, make a copy on your system. You’ll want to save the Match-Maker-Breaker spreadsheet file for each trio of people individually, and you’ll want a fresh Match-Maker-Breaker spreadsheet copy to run with each new set of download files.

Instructions

I’m not going to repeat Philip’s instructions here, but please read them entirely before beginning and please follow them exactly. Philip has included graphic illustrations of each step to the right of the instruction box. The spreadsheet opens to the Instructions page. You can print the instruction page as well.

Copy/Pasting Data

When copying the parents’ and child’s data into the spreadsheets, do NOT copy and paste the entire page by selecting the page. Select and copy the relevant columns by highlighting columns A through G by touching your cursor to the A-G across the top, as shown below.  After they are selected, then click on “copy.” In the child’s chromosome browser download spreadsheet, position the curser in the first cell in row 1 in the child’s page of the Match-Maker-Breaker spreadsheet and click on “paste.”

Do NOT select columns H-K when highlighting and copying, or your paste will wipe out Philip’s formulas to do calculations on the child’s tab on the spreadsheet.

The example above, assuming that Annie is the last entry on the spreadsheet, shows that I’ve highlighted all of the cells in columns A-G, prior to executing the copy command. Your spreadsheets of course will be much longer.

I wrote a very quick and dirty article about using Excel here

The Match Making Breaking Part

After you copy the formulas from rows H2 to K2 through the rest of the spreadsheet by following Philip’s instructions, you’ll see the results populating in the status bar at the bottom. You’ll also see colors being added to the matches on the left hand side of the spreadsheet page and counts accruing in the 4 right columns. Be patient and wait. It may take a few minutes. When it’s finished, you can verify by scrolling to the last row on the child’s page and you’ll see something like the example below, where every row has been assigned a color and every match that matches the child and the father, mother, both or is found in the HLA region is counted as 1 in the right 4 columns.

In this example, 5 segments, shown in grey, don’t match anyone, one, shown in tan is found in the HLA region, and three match the father, in blue.

Output

After you run the Match-Maker-Breaker tool, the child’s matches on the Child tab will be identified as follows:

This means that segment of the child that matches that individual also matches the father, the mother, both parents, the HLA region, or none of the above on all or part of that same segment.

What is a Match?

Philip and I worked to answer the question, “what is a match?” In the Concepts article, I discussed the various kinds of matches.

  • Full match: The child’s match and parent’s match share the same exact segment, meaning same start and end points and same number of SNPs within that segment.
  • Partial match: The child’s match matches a portion of the segment from the parent – meaning that the child inherited part of the segment, but not the entire segment.
  • Overhanging match: The child’s match matches part or all of the parent’s segment, but either the beginning or end extends further than the parents match. This means that the overlapping portion is legitimate, meaning identical by descent (IBD), but the overhanging portion is identical by chance (IBC.)
  • Nested match: The child’s match is smaller than the match to the parent, but fully within the parent’s match, indicating a legitimate match.
  • No match: The person matches the child, but neither parent, meaning that this match is not legitimate. It’s identical by chance (IBC).

Full matches and no matches are easy.

However, partial matches, overlapping matches and nested matches are not as straightforward.

What, exactly, is a match? Let’s look at some different scenarios.

If someone matches a parent on a large segment, say 20cM, and only matches the child on 2cM, fully within the parent’s segment, is this match genealogically relevant, or could the match be matching the child by chance on a part of the same segment that they match the parents by descent? We have no way to know for sure, just utilizing this tool. Hopefully, in this case, the fact that the person matches the parent on a large segment would answer any genealogical questions through triangulation.

If the person matches the parent but only matches the child on a small portion of the same segment plus an overhanging region, is that a valid match? Because they do match on an overhanging region, we know that match is partly identical by chance, but is the entire match IBC or is the overlapping part legitimate? We don’t know. Partly, how strongly I would consider this a valid match would be the size of the matching portion of the segment.

One of the purposes of phasing and then looking at matches is to, hopefully, learn more about which matches are legitimate, which are not, and predictors of false versus legitimate matches.

Relative to this tool, no editing has been done, meaning that matches are presented exactly as that, regardless of their size or the type of match. A match is a match if any portion of the match’s DNA to the child overlaps any portion of either or both parent’s DNA, with the exception of part of chromosome 6. It’s up to you, as the genealogist, to figure out by utilizing triangulation and other tools whether the match is relevant or not to your genealogy.

If you are not familiar with identical by descent (meaning a legitimate match), identical by population (IBP) meaning identical by descent but because the population as a whole carries that segment and identical by chance (IBC) meaning a false match, the article Identical by…Descent, State, Population and Chance explains the terms and the concepts so that you can apply them usefully.

About Chromosome 6

After analyzing the results of several people, the area of chromosome 6 that includes the HLA region has been excluded from the analysis. Long known to be a pileup region where people carry significant segments of the same DNA that is not genealogically relevant (meaning IBP or identical by population,) this region has found to be often unreliable genealogically, and falls outside the norm as compared to the rest of the segments. This area has been annotated separately and excluded from match results. This was the only region found to universally have this effect.

This does not mean that a match in this region is positively invalid or false, but matches in the HLA region should be viewed very skeptically.

The Results Tab – Statistics

Now that you’ve populated the spreadsheet and you can see on the Child tab which matches also match either or both parents, or neither, or the HLA region, go to the Results tab of the spreadsheet.

This tab gives you some very interesting statistics.

First, you’ll see the number and percent of matches by chromosome.

The person compared was a female, so she would have X matches to both parents. However, notice that X matching is significantly lower than any of the other chromosomes.

Frankly, I’ve suspected for a long time that there was a dramatic difference in matching with the X chromosome, and wrote about it here. It was suggested by some at the time that I was only reporting my personal observations that would not hold beyond a few results (ascertainment bias), but this proves that there is something different about X chromosome matching. I don’t know what or why, but according to this data that is consistent between all of the beta testers, matching to the X chromosome is much less reliable.

The second statistics box you will see are statistics for the matches to the child that also match the parents. The actual matches of the child to the parents are shown as the 23 shown under “excluded from calculations.”

The next group of statistics on your page will be your own, but for this example, Philip has combined the results from several beta testers and provided summary information, so that the statistics are not skewed by any one individual.

Next, the match results by segment size for chromosomes 1-22. Philip has separated out segments with less than 500 SNPs and reports them separately.

You will note that 90% or more of the segments 9 cM and above match one of the two parents, and 97% or more of segments 12cM or above.

The X chromosome follows, analyzed separately. You’ll notice that while 27% of the matches on chromosomes 1-22 match one or both parents, only 14% of the X matches do.

Even with larger segments, not all X segments match both the child and the parents, suggesting that skepticism is warranted when evaluating X chromosome matches.

Philip then calculated a nice graph for showing matching autosomal segments by cM size, excluding the X.

The next set of charts shows matches by SNP density. Many people neglect SNP count when evaluating results, but the higher the SNP count, the more robust the match.

Note that SNP density above 2,200 almost always matched, but not always, while SNP density of 2,800 reaches the 97% threshold..

The X chromosome, by SNP count, below.

X segment reach the 100% threshold about 1600, however, we really need more results to be predictive at the same level as the results for chromosomes 1-22.  Two data samples really isn’t adequate.

Once again, Philip prepared a nice chart showing percentage of matching segments by SNP count, below.

Predictive

In the Segment Survival – 3 and 4 Generation Phasing article, one can see that phased matches are predictive, meaning that a child/parent match is highly suggestive that the segment is a valid segment match and that it will hold in generations further upstream.

Several years ago, Dr. Tim Janzen, one of the early phasing pioneers, suggested that people test their children, even if both parents had already tested. For the life of me, I couldn’t understand how that would be the least bit productive, genealogically, since people were more likely to match the parents than the children, and children only carry a subset of their parent’s DNA.

However, the predictive nature of a segment being legitimate with a child/parent match to a third party means that even in situations where your own parent isn’t available, a match by a third party on the same segment with your child suggests that the match is legitimate, not IBC.

In the article, I showed both 3 and 4 generations of phased comparisons between generations of the same family and a known cousin. The results of the 5 different family comparisons are shown below, where the red segments did not phase or lost phasing between generations, and the green segments did phase through multiple generations.

Very, very few segments lost phasing in upper (older) generations after matching between a parent and a child. In the five 4-generation examples above, only a total of 7 groups of segments lost phasing. The largest segment that lost phasing in upper generations was 3.69 cM. In two examples, no segments were lost due to not phasing in upper generations.

The net-net of this is that you can benefit by testing your children if your parents aren’t available, because the matches on the segment to both you and the child are most likely to be legitimate. Of course, there will be segments where someone matches you and not your child, because your child did not inherit that segment of your DNA, and those may be legitimate matches as well. However, the segments where you and your child both match the same person will likely be legitimate matches, especially over about 3.5 cM. Please read the Segment Survival article for more details.

If you want to order additional Family Finder tests for more family members, you can click here.

Group Analysis

Philip has performed a group analysis which has produced some expected results along with some surprising revelations. I’d prefer to let people get their feet wet with this tool and the results it provides before publishing the results, with one exception.

In case you’re wondering if the comparisons used as examples, above, are representative of typical results, Philip analyzed 10 of our beta testers and says the following:

The results are remarkably consistent between all 10 participants. Summing it up in words: with each person that you match you will have an average of 11 matching segments. Three will be genuine and will add to [a total of] 21 cM. Eight will be false and add to [a total of] 19 cM.

Philip compiled the following chart summarizing 10 beta testers’ results. Please note that you can click to enlarge the images.

The X, being far less consistent, is shown below.

We Still Need Endogamous Parent-Child Trios

When I asked for volunteer testers, we were not able to obtain a trio of fully endogamous individuals. Specifically, we would like to see how the statistics for groups of non-endogamous individuals compare to the statistics for endogamous individuals.

Endogamous groups include people who are 100% Jewish, Amish, Mennonite, or have a significant amount of first or second cousin marriages in recent generations.

Of these, Jewish families prove to be the most highly endogamous, so if you are Jewish and have both Jewish parents’ DNA results, please run this tool and send either Philip or me the resulting spreadsheet. Your results won’t be personally identified, only the statistics used in conjunction with others, similar to the group analysis shown above. Your results will be entirely anonymous.

Philip’s e-mail is philip.gammon@optusnet.com.au and you can reach me at roberta@dnaexplain.com.

Caveat

Philip has created the Match-Maker-Breaker tool which is free to everyone. He has included some wonderful diagnostics, but Philip is not providing individual support for the tooI. In other words, this is a “what you see is what you get” gift.

Thank You and Acknowledgements

Of course, a very big thank you to Philip for creating this tool, and also to people who volunteered as alpha and beta testers and provided feedback. Also thanks to Jim Kvochick for trying to coax Numbers into working.

Match-Maker-Breaker Author Bio:

Philip’s official tagline reads: Philip Gammon, BEng(ManSysEng) RMIT, GradDipSc(AppStatistics) Swinburne

I asked Philip to describe himself.

I’d describe myself as a business analyst with a statistics degree plus an enthusiastic genetic genealogist with an interest in the mathematical and statistical aspects of inheritance and cousinship.

The important aspect of Philip’s resume is that he is applying his skills to genetic genealogy where they can benefit everyone. Thank you so much Philip.

Watch for some upcoming guest articles from Philip.

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Disclosure

I receive a small contribution when you click on some of the links to vendors in my articles. This does NOT increase the price you pay but helps me to keep the lights on and this informational blog free for everyone. Please click on the links in the articles or to the vendors below if you are purchasing products or DNA testing.

Thank you so much.

DNA Purchases and Free Transfers

Genealogy Services

Genealogy Research