First Look at Chromosome Analysis

One of the most common questions I hear from genealogists who have been using DNA for a few years is: “I’ve worked through my DNA matches and shared matches. What do I do next?”

For many researchers, the answer is chromosome analysis. 

The term can sound a little intimidating. It conjures up images of complicated charts, coloured segments and advanced genetics. In reality, chromosome analysis is simply another way of looking at the DNA evidence we already have.

It allows us to move beyond asking who we match and begin exploring how that DNA was inherited.

Looking Beyond the Match List

Most of us begin our DNA journey with match lists.  

We look at the amount of DNA shared with a match, examine shared matches and hopefully identify a common ancestor. These tools remain the foundation of genetic genealogy and are often all we need to solve a problem.  However, sometimes we reach a point where the match list no longer provides enough answers.

Perhaps we have identified a cluster of related matches but cannot determine which ancestral line they belong to. Maybe we share multiple possible common ancestors? Or perhaps we simply want greater confidence in our conclusions.

This is where chromosome analysis can help.

What Exactly Are We Looking At?

Each of us inherits 23 chromosomes from our mother and 23 chromosomes from our father.

As DNA is passed from generation to generation, those chromosomes are broken apart and recombined. The chromosomes we inherit today are therefore a patchwork of DNA segments contributed by many different ancestors.

Every segment has travelled through a chain of ancestors before reaching us.

Chromosome analysis allows us to examine those segments and ask questions such as:

• Which ancestor contributed this piece of DNA?
• Which matches inherited the same segment?
• Can we identify the ancestral line responsible for that segment?
• Does the segment support our documentary research?

These questions take us beyond simple matching and into the realm of DNA evidence.

Each chromosome contains millions of DNA markers inherited through generations of recombination.

 Understanding how chromosomes are structured is the first step towards chromosome analysis.

Chromosome Browsers

A chromosome browser is simply a tool that displays where DNA segments are shared between two or more people.

Instead of seeing only a total amount of shared DNA, we can see exactly where those shared segments occur on a chromosome.  Several testing companies and third-party tools provide chromosome browsers, including MyHeritage and GEDmatch.

For many researchers, the chromosome browser is their first introduction to segment analysis.  At first glance it may look like a collection of coloured bars. With practice, however, those coloured bars begin to tell stories about inheritance and ancestry.

A chromosome browser allows us to see exactly where DNA is shared between two or more individuals

 rather than simply reporting a total amount of shared DNA.

Why Segments Matter

Imagine two DNA matches who both descend from the same ancestral couple.

If they inherited the same segment of DNA from that ancestral line, we would expect them to share DNA with us in the same location on a chromosome.  Finding these shared segments provides another piece of evidence that supports the documented relationship.

The segment itself does not prove an ancestor.

Instead, it contributes to a growing body of evidence that can strengthen or weaken a hypothesis.

This distinction is important.

Chromosome analysis does not replace genealogy.  It enhances it.

Introducing Segment Triangulation

One of the most powerful concepts in chromosome analysis is segment triangulation.

In simple terms, segment triangulation occurs when three or more people:

• Share the same segment of DNA.
• Match each other on that segment.
• Can trace their ancestry to a common ancestral line.

When these conditions are met, we can often be more confident that the segment was inherited from that ancestral line.

Triangulation helps move us from a collection of matches towards a clearer understanding of how DNA has been inherited.

For many genealogists, this is the point where chromosome analysis becomes truly useful.

Members of a triangulated group all share the same segment of DNA and match one another on that segment.

This can provide strong evidence that the segment came from a shared ancestral line.

Building a Chromosome Map

Over time, triangulated segments can be assigned to specific ancestral lines.

As more segments are identified, a chromosome map begins to emerge.

A chromosome map is simply a visual representation of which parts of our DNA were inherited from different ancestors.

Each newly identified segment adds another piece to the puzzle.

The process is gradual. Few people build a complete chromosome map overnight. Instead, it develops through ongoing research, collaboration and evidence gathering.

By combining documentary research, shared matches and triangulated groups, DNA segments can gradually be mapped to ancestral lines and usually to individual ancestors.

Validating Your Family Tree

One of the most valuable applications of chromosome analysis is tree validation.

Traditional records tell us who we believe our ancestors were.

DNA provides an independent source of evidence.

When documentary research, shared matches, triangulated groups and mapped segments all point towards the same conclusion, our confidence in that conclusion increases.

This is one of the reasons chromosome analysis has become an increasingly important tool for genetic genealogists.

Traditional records tell us who our ancestors were. DNA evidence helps test those conclusions. By combining documentary research with chromosome analysis, we can gradually build confidence in the relationships shown in our family tree.

Taking the Next Step

Chromosome analysis is not about replacing shared matches.

It is about building upon them.

Shared matches help us identify people who may be connected to us.

Segments help us understand how that connection was inherited.

Chromosome analysis becomes even more powerful when combining cluster analysis, triangulated groups and chromosome mapping.  The techniques can help us move beyond just identifying matches and to begin identifying ancestral lines—and the individual ancestors—responsible for the DNA we share today.

In many ways chromosome analysis is simply the next stage of genetic research process.  It allows us to move beyond asking who matches who and to explore and confirm exactly which ancestor handed down the DNA we share.  While the techniques may appear complex at first, the underlying principles are surprisingly straightforward - more like a logic puzzle, providing valuable insights into our family history.

REMEMBER

• Shared matches and clusters help us identify people who may be related.

• Chromosome analysis helps explain how the DNA was inherited.

Together, they provide a richer understanding of our family history.

Veronica Williams

First published 3 Jun 2026

Last updated 16 Jun 2026

Digging into segments - in the absence of reports from My Heritage

I have long been a fan of segment analysis to find your common ancestor.  The last couple of years have been particularly frustrating since DNA companies have turned off their downloads for segment data.  

Having downloaded most of my matches regularly to the Genealogical DNA Database Tool (GDAT) this issue was manageable in what I thought would be the 'short term' as I had plenty of matches to explore and could easily look at isolated segment data on some sites.  AncestryDNA's release of Enhanced Shared Matching late last year also kept my interest up for a time and is proving to be invaluable, but I find myself exploring and building family groups for matches that are not my priority.  Was this the best use of my time in finding my nemesis ancestor, my 2nd great grandfather George Courtney!

Using Visual Phasing techniques I have identified all the likely segment areas that have come from the 'Courtney line'.  Two sets of siblings, my mother and three of her siblings (RM siblings), plus another four siblings, children of Mums paternal first cousin (RR siblings).  How can I interrogate new matches in these segment areas without downloadable lists?  

4 RM Siblings: Segments by Grandparent on Chromosome 4  

There are bound to be new matches in these locations, but how do I find them?  Continually visiting known matches in each segment location for the 10 kits relevant to the search was a long winded and laborious exercise, always hoping for a miracle.  The relevant matches are not likely to be 'big' unknown matches, the key ones are more likely to be buried in the smaller matches, much harder to find.

Whilst GEDmatch and FTDNA have segment reports, there are few new matches and few trees.  The My Heritage site was my best bet, providing segments, triangulation tools and many trees.  Using tools like Pedigree Thief it is possible to obtain match lists providing Total cMs, this has helped find new larger matches, but it is difficult to identify specific ones that might be paternal matches of interest for me.  I had to work through each one by one, extract the segment data and then compare to my Visual Phasing output.  On most occasions it turned out the match was not in the segment area of interest.  I tried to consider how this could be a more productive process.

I have never been a big user of the label (dots) system at My Heritage given there are so many false positives appearing in the shared match list.  This being mainly due to the small match threshold of 6cMs and at times imputation.  At AncestryDNA many of these old population segments have been eliminated by their Timber algorithm.  At My Heritage, I always prefer to add matches to an 'ancestral couple' label ONLY when there is a triangulated segment.  This way, poor label allocation doesn't lead to new matches being incorrectly labelled in the future.  It was time to revisit my process.

I started to consider how Pedigree Thief, the new fabulous Genealogy Assistant (chrome extension) and Labels at My Heritage could help me to better identify and prioritise key matches for segment analysis.

Starting with Labels

My current labels were already organised by ancestral couples.  For my Courtney project, I have 10 primary kits (plus 4 descendants) at My Heritage that need analysing in a priority order, shared segments between kits, then each kit needs examining for segments that were only inherited by them.  The Courtney line is on Mum's paternal side, so I started with her matches and the 4 sibling kits of the children of her paternal first cousin (RRS) who share the Roberts-Courtney line.  I decided to create labels for each of the RR siblings and then another label for matches who triangulate with one or all of them, as these matches would be my priority.  As we are talking large numbers of shared matches, I recommend loading the Genealogy Assistant.  These cousin siblings each had between 551-772 shared matches with my Mum.  As both sets of Roberts siblings have mostly Irish maternal sides, there are a lot of shared matches that are old population segments and false positives that need to be 'weeded out' to be left with only valid Roberts-Courtney matches.

1. Navigate to the shared match page for the tester (in my case Mum) and the key match (RRS, sibling 1);
2. Go to the bottom of the shared match page and use the field shown for auto-load pages and put in an estimate of the number of pages needed (Genealogy Assistant must be loaded).
3. Navigate back up to the top of the list and slowly scroll through to the end of the match list. You will know when you are at the end when the 'Show more DNA Matches' disappears.
4. Once again, navigate up to the top of the list.  Click on the 'select all matches' button (Genealogy Assistant).  Before choosing a label watch the 'Manage Labels' count and let it get to the maximum number of matches selected.
5. Select an existing label or 'Create a new label'.  Click Apply'.  If you have large numbers of matches, then you may get a spinning wheel for a while and the page appears to have hung.  Wait a decent length of time for it to finish.  I have found that if you open the shared match page in another window and check if the last person has been labelled, it has usually completed the process.
6. While all the matches are selected we are next going to identify all the triangulated matches to add to our combined 'Matches TG - RRS' label.  If your results are like mine there are more triangulated matches than un-triangulated matches.  If so, remove the tick from everyone who does not have the triangulated group symbol.  Otherwise, do the reverse.  If you wait until later to do this part, when you 'select all matches' again, make sure to wait and watch the 'Manage Labels' count before selecting the new label.
7. Add the reduced number of matches to the 'Matches TG - RRS' label.
8. Repeat the process for other key matches (in this example the next 3 RR siblings), adding triangulated matches to the same 'Matches TG - RRS' label.

My mother had 16,566 matches at My Heritage when undertaking this exercise.  After this process, the total number of shared matches for the RR siblings was 1463 and of those, 1043 were triangulated.  

As the 1043 matches were all triangulating with Mum and at least one RR sibling we know each of them must have inherited the segment from the same common ancestor.  As a result, we can be confident that the segment shared between the two sets of siblings (RM and RR), was inherited from their shared MRCA being the 'Roberts-Courtney' couple - Edward Roberts (Baker/Dye) and Abigail Courtney.  How each of the 1043 matches are related is yet to be determined, but it will be back on one of either the Roberts OR Courtney lines.  These 1043 can now also be labelled to the 'Roberts-Courtney' ancestral group (NOTE:  The Roberts-Courtney group is an existing label for the 'ancestral couple'.  It will contain other matches already identified through DNA analysis and may be larger than the newly created  'Matches TG - RRS' label). 

1. Navigate back to the main match page and select 'Filters'.  Go to 'Labels' and select the consolidated TG group - 'Matches TG - RRS'. 
2. With the Genealogy Assistant 50 matches will appear on each page in this view.  With 1043 matches we have 21 pages to process.  Starting on page 1 navigate to the top of the match list to 'select all matches'. Then choose the appropriate label (in this case  'Roberts-Courtney'), select 'Apply'.
3. Repeat the process with the remaining pages.  Firstly, navigate to the bottom of the list to select the next page number, then navigate to the top to 'select all matches', 'select label', 'apply'.  

If you would like a spreadsheet generated as a list of these matches, enter the total number of pages and click the 'Download CSV' button.  You must have the Genealogy Assistant loaded for this option to appear.  You will need to wait for each page to populate and process all the pages before the CSV will be ready to download to your computer.

The spreadsheet contains the match name, estimated relationship, shared Total cMs, number of shared segments, largest cMs segment, tree size and the location of the match.  Matches are listed in Total cMs order, but can also be sorted by largest cMs segment to identify priority matches for review.  When reviewing the filtered Label of 'Matches TG - RRS', you can select the 'Sort By - largest segment' to achieve the same result.  

Whilst at this point we have identified 1043 priority matches, we have no way of telling which of them have shared segments in the Courtney grandparent location (Figure: Chromosome 4).

My aim is to isolate all the George Courtney segments.  The next challenge will be to analyse all matches in the 'Matches TG - RRS' group and split them into one of the 4 paternal great grandparent lines: Roberts PGGF (Dye), Laundon PGGM (wife of Edward Roberts), Paice PGGM (wife of George) and finally our mystery PGGF - Abigails father  'George Courtney'!  

The remaining 420 shared matches who do not triangulate with our RR siblings will need additional analysis further down the track.  They may share additional segments not inherited by the RM siblings or they may be false positives or old population segments. At this point we are only prioritising the 1043 triangulated matches as we know they are valid segments and should be reviewed first.

Getting segment data via Pedigree Thief

In the absence of downloads from My Heritage, Pedigree Thief is the only tool I know that can help extract specific segment data at the moment.  It can prove to be difficult at times, as the site imposes limits and sometimes suggests we are doing too much, what it calls 'scraping'.  This can sometimes lead to being temporarily barred from using the site, so we need to minimise each query as much as possible.

We can obtain segment data from My Heritage using Pedigree Thief in two ways:

1. From the main match page, where options are 'with DNA' or 'without DNA'.  I would recommended extracting data here first using 'no DNA' to maximise the number of matches you are adding to the Pedigree Thief database.
2. From the shared match list, you can extract shared matches, ICW and trangulations.  It will not work if the selected match is not already in the database and you will be directed back to the main match page.

My suggested process is aimed at gathering as much segment data as possible for the priority matches identified as triangulated with the RR Siblings, accessed via the filtered Label of 'Matches TG - RRS'.

1. Firstly, navigate back to the main match page and select 'Filters'.  Go to 'Labels' and select the consolidated TG group - 'Matches TG - RRS'. 
2. Navigate up to the ribbon toolbar (next to the search bar) and select the 'Pedigree Thief' icon (you must have already downloaded Pedigree Thief from the Chrome store for this to appear).
3. You can only read 5 pages of matches at a time, select 5 and Read Matches (no DNA).  When the first 5 pages are finished, continue to select the next 5 pages until all are done.
4. Click the 4 'save boxes', these should produce the following files downloaded to your computer:
• MyHeritage Matches for XXX;
• MyHeritage Shared DNA for XXX;
• MyHeritage ICWs for XXX; and 
• MyHeritage Triangulations for XXX.

These files can be imported into GDAT using the approved templates.  Don't be fooled by the names,  "Read Matches (no DNA) means no 'segment' DNA - it includes Total cMs for all matches.

Once this is loaded we can go back to the shared match page:

1. Navigate to the shared matches of your tester and the key match (for my example, Mum and an RR sibling);
2. Use the Auto-load page feature again (Genealogy Assistant) and keep scrolling down the list until all the shared matches have loaded and you have one page of matches;
3. Scroll up to the toolbar and click on the Pedigree Thief icon.  As I have 695 in this list I am going to start by selecting 'Read matches (no DNA)' to extract more data into the Pedigree Thief database.  The tool collected 695 ICW and Triangulations and says 530 are queued for triangulation.  The output is a downloadable ICW file, which can be loaded into GDAT.
4. Next I want to Read Matches (and DNA) but this is where we need to be conscious of potential system overuse.  The system will only review a certain number of these matches, mine stopped at about 100.  The tool now says it has collected 695 ICW, 38 Triangulations and that 432 are queued for triangulation.  The output now includes a downloadable chromosome data file, which can be loaded into GDAT.  The chromosome data is the DNA shared between your tester and the key match (for my example, Mum and RR sibling 1).  Using this process on more distant known cousins would provide a much more manageable number, but these matches are critical for my research project.
5. The ICW file is the same as the one earlier, but the triangulation file is also able to be downloaded and added to GDAT.  It contains chromosome data from the 38 matches it has collected already.  We can now target any of these matches that have segment data in the target segment areas (ie. Courtney segments).

Next we have two options, continue to complete the remaining 432 matches queued for triangulation or to work with the chromosome data we have collected so far (eg the 38 matches).  My preference is to load all the data so I can identify all the matches in the likely segment locations, but MH system constraints may require you to do just one page at a time. 

1. Return to Pedigree Thief to continue gathering the triangulation data - go to the triangulations queued and click 'read'.  You may get a message that you have reached your limit for the day.  If this is the case stop gathering and review the matches you have so far.  Come back later, you don't want to have your subscription suspended.  If you are using GDAT you should be able to review the triangulated matches and see who else is ICW on the segment given that file has already been loaded, even though you don't have all their chromosome data yet.  Make sure to hit the down arrow and you have the option to click 'ALL' - matches, segments, in common with and triangulation files.
2. Pedigree Thief also allows you to gather data for just one match.  The chromosome data spreadsheet for the 38 matches included 7 who were in the 'Courtney' segment location on chromosome 4.  Unfortunately the chromosome data spreadsheet downloaded from Pedigree Thief does not contain match names, just a My Heritage Relative ID.  You can search for the match in GDAT using the 'Search Match Key' option and entering the My Heritage Relative ID.  
3. Once you have found the match in GDAT use the hotkey to navigate back to the match at My Heritage.  Select the Pedigree Thief icon and extract the data using 'Read Match (and DNA)'.  This will produce 4 files to be downloaded - match, chromosome data, ICW and triangulation.  We already have the match and shared DNA in the GDAT database so we don't the first two, but upload ICW and triangulations to GDAT.
4. As you investigate your matches in the priority segment areas in GDAT, make sure to also add a note on the match's page in your consolidated TG label at My Heritage (eg. 'Matches TG - RRS') so that your can monitor your progress on all the triangulated matches.  
5. Continue in this way until all those in the TG label have been reviewed and have segment data in the priority groups are uploaded to GDAT.  
6. Where Visual Phasing or other segment analysis processes have identified the likely ancestral couple for each segment location, review each match in the consolidated TG label at My Heritage (eg. 'Matches TG - RRS') make a note to that effect, then add another label for the known ancestral couple and remove the match from Roberts-Courtney label.  For my tree these would be Dye-Laundon (Roberts side) or Paice-Parker (wife of George Courtney).  Even if we don't know the name of our MRCA with a match, the aim is to move all 1043 matches over time from the grandparent label (Roberts-Courtney) into the correct ancestral couple label (one of the 4 great grandparent lines).
7. As I review each TG (ideally removing it from the Robert-Courtney group), I update the label for the match and mark all the TG matches to their new ancestral group at the same time.  This reduces rework when reviewing new triangulated matches down the track.  
8. Matches who can't be allocated to a new 'ancestral couple' label should remain in the 'Roberts-Courtney' group.  You may wish to create an additional label for those that have been reviewed, but were unable to be allocated to a new label.
9. If you are reviewing multiple kits, it is a good idea to get all kits to the 'Matches TG - RRS' stage, then use the Genealogical Assistant to download a csv of each kits matches.  Combining them into an alphabetical .csv will give you an idea of the total number of matches needing review, plus you can keep track of those already reviewed as you progress further through all kits. Whilst I make notes in My Heritage and GDAT as I go, a paper list can sometimes be easier to manage in terms of checking back when working on subsequent kits.
10. Continue to review the Roberts-Courtney label for all matches who also have the label 'Matches TG - RRS' (sadly labels at MH do not cater for a sort of matches with both these labels) until all those matches have ben moved to an ancestral group label or the best case scenario - the number of matches in the group is exhausted. When reviewing the matches with this label, sort them using largest segment, so that priority segments are reviewed first ie.  a person with a single 35cMs segment is likely to be a better match to review that someone sharing 35cMs over 4 segments.
11. Repeat the process for the other key testers (ie. the remaining 3 RM siblings) and other associated kits.
12. Always remember when reviewing shared matches to check if your key match cousins or siblings have larger segments than your main tester (in my case Mum).  If they have larger segments make them the key kit for the analysis of that Triangulated Group as their shared matches will be in a larger segment location, ie. there will be a broader pool of triangulated matches to assist in identifying the MRCA for that group.

The missing link

This process does not help get to those 'likely Courtney segment areas' that the RR siblings do not share with the RM siblings or other associated kits.  The time poor method of looking at known matches and their ICW's in existing segment locations seems the only way to get there at this time.  Some may be buried in the 420, potentially matching on different segments.  If anyone can suggest other methods, please let me know.

Hopefully by the time I've finished reviewing all the matches in my TG Group Label we will have downloads back!

Veronica Williams

First published 7 April 2025

Last updated 25 April 2025

ADDENDUM: 16 April 2025  Following discussion with the developer of Genealogy Assistant, a new button has been introduced to 'Load all' pages, this helps enormously. The blog will be updated soon to streamline the affected steps.  We are also discussing ways to get another sort to reduce the list to just TG matches, more soon, fingers crossed.

My Heritage - Modified exercise to identify triangulated groups using Pedigree Thief

In Module 2 of  'Organising your DNA data and determining match groups' we discussed ways to organise data and a process for working with My Heritage to identify match groups.  Before moving to Module 3, make sure you understand the theory of segment triangulation and have established a method for retaining records of your DNA research, to avoid rework and improve your productivity.

My Heritage is a DNA testing site that allows uploads from other testing companies. It's free to upload, but if you are not a My Heritage subscriber you will be required to pay a small 'one off' unlock fee to access DNA tools.  My Heritage has usually has two downloads that are useful for chromosome analysis, however these are currently DISABLED.

In the 2021 and 2023 programs we completed an exercise at My Heritage to consolidate your understanding of how to determine triangulated segments, identify potential match groups and whether a match is likely to be a false positive. It is not possible to do that for the 2024 program given the reports are unavailable.  

For the 2024 program, this modified 'Module 2: Exercise 2' seeks to use My Heritage data to continue to practicing analysing your matches manually to ensure you appreciate the underlying theory of shared matches vs triangulated segment matches to identify potential match groups.  Remember, whilst shared matches are 'CLUES' of a shared ancestor, only shared and triangulated segments are 'EVIDENCE' of a common ancestor.  Unfortunately due to the downloads being disabled we cannot extend the exercise to assess whether other matches are false positives, however 'Module 2: Exercise 1' using GEDmatch does attempt to cover this.

Due to download data not being available from My Heritage, we are going to use 'Pedigree Thief' a tool made available by loading a chrome extension, to help speed up some of the manual data collection.

My Heritage also has a clustering tool which can assist you to determine where to start your research, but this is best utilised once you understand more about triangulation.  The clusters are an indication of matches in common, however understanding segment triangulation and how triangulated groups are formed will assist you to analyse the clusters more fully, helping to identify the key matches in the cluster more likely to share a common ancestor.

The following activities are suggested to help you apply 'Module 2' in practice.  If you have access to old downloaded data from My Heritage I recommend you complete the original exercise after completing the activities outlined in this blogpost.

Setting Up Pedigree Thief

First, you will need to download Pedigree Thief from the Chrome Web Store and update your browser.  Once loaded you should see the icon symbol above on your browser adjacent to the search bar. Before using it for the first time, right-click the icon symbol and select 'Help' from the menu. This will give guidance to setting up and using the extension. For further help join the Pedigree Thief Facebook Group.

Pedigree Thief also extracts pedigrees (as the name implies) and is an extremely useful product for that purpose. We will discuss that more in Module 3.

Part A:  Using the Broad Approach by Total cMs - My Heritage www.myheritage.com

The 'DNA matches list' which can normally be downloaded from My Heritage for each DNA kit is currently disabled.  This makes it difficult to analyse your match list by chromosome.  As a result, we are going to use Pedigree Thief to download the data that we need; it will also assist in reducing the amount of typing you have to do.  We are not going to be able to extract everything required, nor is it in the perfect format.  Hopefully, downloads will return soon and this is just a short term 'semi' solution.

1. Login to My Heritage site and navigate to your DNA Matches list.
2. First, review at least your top 5 matches at My Heritage that are not people you have tested or close family.  We want to ensure we know where our highest matches fit in, make sure to examine all those >100cMs.
3. Next we are going to extract data using Pedigree Thief to start creating our master match list.  Unfortunately until the download reports return, much of our data will need to be downloaded one match at a time and slowly add to our list.
4. Go to the My Heritage DNA Matches Page for your kit.  If the top 5 matches you want to examine are not all in the first 10, go to the bottom of the page and expand the view to 25.
5. The first time you access Pedigree Thief by clicking on the icon in your browser the screen shown below will appear.  Don't worry if you don't see all these fields, we just need the first section at the moment.  
6. Leave the number of pages to read at 1, then click on 'Read Matches'.  Pedigree Thief will read the matches on the page - either 10 or 25 depending on your selected view. 
7. Once Pedigree Thief finishes its review (screen stops changing), click again on the Pedigree Thief icon and the screen will re-appear, usually with additional fields.
8. Click the options to save, we want 'All Matches' and 'All Segments'.  The two files should be produced and saved to your download folder.  We are only working with the 'MyHeritage Match ....'  file for this part of the exercise.
9. Retain the 'Shared DNA file'  for later use.

Updating your sheet

1. Go to your Downloads folder and find the 'MyHeritage Match ....' file.
2. Duplicate the 'MyHeritage Match ....' file and rename it 'My Heritage Match List, Total Shared cMs - Kit_IDXXXX'
3. Add 3 new columns to your spreadsheet - Side, MRCA and Notes.
4. Your My Heritage Match List, Total Shared cMs - Kit_IDXXXX' spreadsheet should have populated with a number of matches.
5. Review the matches, do you know if they are maternal or paternal (or both - ie share both sides, close relations)?  Don't worry if you are not able to allocate sides at this stage.
6. Think about the likely relationship, how many generations back in your tree might you expect to find the MRCA? (In Module 1 we discussed the Shared cMs tool to predict relationships?  You might like to compare those estimates to those in the My Heritage prediction column).
7. Notate your spreadsheet with the known or likely MRCA couple if you can, this is not essential.
8. Over time, the 'My Heritage Match List, Total Shared cMs - Kit_IDXXXX' spreadsheet will become your master list as you add data to the spreadsheet. Add any other matches you examine in this exercise to your list, to avoid future re-work.

You should end up with a sheet that looks something like the one below.

Part B:  Using Chromosome Analysis (Targeted Approach) - My Heritage www.myheritage.com

In Part B we want to examine a 'match of interest' who only shares on one segment (to make it easier to interrogate) so Joan's match #6 with 'Ian' would be suitable.  If your first 'match of interest' shares more than 1 segment, you will need to drill down further in the list to find another potentially suitable match to examine for this exercise.  

Matches sharing more than one segment will have mix of ICW (in common with) matches who may all share on different segments.  By choosing a match who only shares one segment - all 'triangulated' ICW matches should share on the same segment.  This will make the exercise more manageable.

For this exercise we are going to utilise the 'Shared DNA file .csv' you have already downloaded, to create a master 'Shared DNA' spreadsheet.

Step 1.  Prepare the spreadsheet:

1. Open the first 'Shared DNA file .....csv' you downloaded via Pedigree Thief and duplicate it.
2. Next, save it as a separate sheet and give it a working title, ie 'My Heritage Shared DNA file - Kit_IDXXXX'.
3. Add 4 new columns to your spreadsheet - Side, TG#, MRCA and Notes.
4. You may wish to hide the 2 Match ID columns and the 2 RSID columns to make the sheet more manageable.
5. Sort the spreadsheet by chromosome, then start and end locations.

You should end up with a sheet that looks something like the one below.

NOTE:   You may prefer to use the My Heritage system for recording your overall notes and not wish to retain a separate master 'match' list, but the shared DNA file is essential for chromosome analysis.   It comes down to personal preference, over time you will work out what works best for you.

Step 2.  Extract data about our 'match of interest' from Pedigree Thief

1. Login to My Heritage site and navigate to your DNA Matches list.  Search for the DNA match of interest and click on the purple 'Review Match List' button to open up the relatives page.
2. Click on the Pedigree Thief icon in your browser toolbar as we did in Part A and read the match.  In this case there are 123 shared matches and in the first read, Pedigree Thief limited the search to 100 matches. 
3. Next, you will need to click on the 'Read Match' radio button again for Pedigree Thief to analyse all the shared matches.  If there are many more shared matches you need to repeat this step until all matches are read.
4. When the read is complete and all shared matches analysed, click the 4 radio buttons to produce files that will save to your downloads folder as we did in Part A.  Note in the completed read image below, of the 123 shared matches only 18 triangulations were identified.
5. Add the information included in 'MyHeritage Match ....'  file  to your My Heritage Match List, Total Shared cMs - Kit_IDXXXX' file, if it is not already there.
6. Add the information included in 'MyHeritage Shared DNA ....'  file  to your My Heritage Shared DNA file - Kit_IDXXXX', if it is not already there.
7. Retain the 'ICW' and 'Triangulations' files for later use.

Initial Read

Completed Read

Notes about the Pedigree Thief files

• The 'MyHeritage ICW ....'  file produces a list of all shared matches with your match but only includes the total cMs shared.  You may wish to consolidate these reports into another master file similar to the ones we created earlier, but this is optional.  Not all of these matches will share a common ancestor with you, but can be 'clues'.  For our purposes we are more interested in 'shared segments' and 'trianguation' data as 'evidence' of a shared common ancestor. 
• The 'MyHeritage Triangulation ....'  file produces a list of all triangulations it encountered in the read of the match and details the match ID's and segments.  It is not easily imported into our My Heritage Shared DNA file - Kit_IDXXXX' but is a useful reference tool. Again, you may wish to consolidate these reports into another master file similar to the ones we created earlier, but this is optional. 

Both these files are designed to be imported into GDAT (Genealogical DNA Analysis Tool).  However, match and shared DNA data for GDAT relies on the My Heritage download files that are currently disabled.  We are in a very difficult position at present.  My suggestion is to upload the individual segment data to your My Heritage Shared DNA file - Kit_IDXXXX' using the process outlined in Part A.

Step 3.  Review triangulated segments for our match of interest on the My Heritage site

1. Login to My Heritage site and navigate to your DNA Matches list.  Search for the DNA match of interest and click on the purple 'Review Match List' button to open up the relatives page.
2. On your match's DNA matches page, the number of shared matches should be the same as the numbers shown in the Pedigree Thief 'Read'.  In my case, the match of interest 'Ian' has 123 shared matches listed on the My Heritage page.
3. We are now going to examine the 'Triangulated segments' at My Heritage for our match of interest.  Work through the match list looking for the Triangulated Segment Symbol, shown in the orange box below.  Identify each match with the 'Triangulated symbol' - because our match of interest 'Ian' only shares on one segment, all the triangulated matches should also share on the same segment.
4. When you get to the bottom of the page, click on the purple 'Show More Matches' box to examine more matches, work in this way until the last page.

Concurrently work with your Pedigree Thief data....

1. As you work through the match list at My Heritage, refer to the The 'MyHeritage Triangulation ....'  file we produced earlier that you put aside.  You might like to ensure that every match with the symbol on My Heritage is also on this list, this is optional.  
2. You should be able to see that all matches are on the same chromosome, in Ian's case - Chromosome 7.  You may wish to add a column for the name of each match which is not included in this report for reasons outlined earlier.  The Relative ID in column 2  of the 'MyHeritage Triangulation ....' file can be searched on  (Control/Command F - using the Relative ID) in the 'MyHeritage ICW ....'  file - it appears in Column 3 and the name of the match is in Column 4.  You can also view the Relative ID when viewing the match at My Heritage in the URL. The Relative ID for the compared match is where the second 'D-' (plus the string of numbers and letters) appears in the address.
3. Pedigree Thief identified 19 triangulated matches for Mum and Ian.  By doing a manual count at My Heritage I found that there were 18 triangulated matches with Mum and Ian, 19 in total including Ian.  As they all triangulate with Mum and Ian on the 'same segment location', they should form a 'triangulated group' and all share a 'common ancestor'.  
4. By examining the 'MyHeritage Triangulation ....' file I can see that all matches match in the same segment area ranging from shared cMs of 17.4 down to 7.3.  You may wish to add your initial match's segment data to this file to be a complete record of matches in this potentially triangulated group.  

Keeping records...

1. My Heritage - If you know which ancestor is likely to have handed down the segment on this chromosome, add each of the triangulated matches to your ancestor group 'Label', including Ian (your match of interest).  In my case, I can tell the segment belongs to the Murphy-Bateman group, by adding the Murphy-Bateman label the each triangulated segment match shows a purple dot.
2. Triangulated Group Data - Decide on a name for the triangulated group you hope to identify for the 'match of interest' from this exercise - it could be TG001-Side A (or whatever name you choose - it can reflect maternal/paternal if you know that information - eg M_001 or something similar).  Rename your 'MyHeritage Triangulation ....' file with your TG # - an example could be 'My Heritage Triangulation  TG1_C07_Maternal' file.
3. You may wish to update both the notes section at My Heritage and your 'My Heritage Triangulation  TG1_C07_Maternal' file with the details of the probable MRCA group/TG name.

Reviewing the Triangulation...

1. Return to your 'MyHeritage Triangulation ....'  renamed  'My Heritage Triangulation  TG1_C07_Maternal' file.  To determine the shared triangulated segment area, we look at the highest start location, then the lowest end location.   
2. Sort the file by start and end locations.  You can see in this example the highest start location is 5.5 but the lowest end location is 5.3.  This indicates that there are likely to be two separate triangulated groups over the length of the match with Ian - he shares between 0 - 9.1.  The full length of the segment area could be coming from just one ancestor, but we must keep in mind for larger segments that the segment could be the mix of an ancestral couple, eg a 2MGGF and 2MGGM.  In this case I would monitor the full segment area between 0-9 as one group until further evidence emerges.
3. Looking at your 'MyHeritage Triangulation ....'  renamed 'My Heritage Triangulation  TG1_C07_Maternal' file, if there are a very large number of triangulated matches all appearing to match on very similar start and end locations, double check that these are not in known false positive regions, or pile up areas.  The chromosome map at DNA Painter is probably the easiest place to check this.  If it is in a known false positive region, use a different match for the exercise, otherwise it may be too time consuming for what we are trying to demonstrate.  Make a note in the notes column.
4. Your sheet should now look something like the one below.  
5. For completeness, run reports with Pedigree Thief for each of the matches appearing in the triangulated group and save the first two reports 'save match data' and 'save chromosome data'.  Add the data contained in these files to your two master sheets we created previously if it is not already there - 'My Heritage Match List, Total Shared cMs - Kit_IDXXXX'  spreadsheet (Part A) and 'My Heritage Shared DNA file - Kit_IDXXXX' spreadsheet (Part B, Step 1).  Add the new details of the TG# number and possible MRCA (if known) to the master sheets.

Key icons for working at My Heritage

Notes on Labelling at My Heritage

My preference for working at My Heritage is to only add Labels on 'triangulated segments'.  It can be dangerous to mark matches as belonging to groups on the basis of a shared matches alone.  My Heritage reports segments down to 6cMs many of these can be false or belong to a different ancestor than other larger segments, ie you may share both a recent and a distant ancestor.  In addition, My Heritage uses imputation which can add segments to your match compared to other companies.  Both these situations can squew results if incorrectly used as the basis for labelling.

To be sure, only label triangulated segments.  Eventually other 'genetic cousins' for that line will all be labelled when analysed via their own DNA match page for the triangulated segments they share.

Part 4.  Review the other side of the chromosome 

Normally, we would examine matches in the same segment area who don't triangulate with our match of interest, to determine if they belong to a 'Triangulated group (TG)' on the other side of the chromosome.  If your match of interest is maternal, those in TG's the other side of the chromosome, in the same segment location, who don't match the maternal group, must be paternal.  Those in the same segment location who do not match either the maternal or paternal TG's, are likely false positive matches and should be discarded. 

As full segment match list downloads have been TEMPORARILY DISABLED by My Heritage (since September 2023!) we cannot complete this step at this stage.  We need to rely on amassing segment data in our master list to eventually be able to achieve this.

Part 5. Is the whole group triangulated?

You can now go back to the 'triangulated match tool' on the My Heritage site and check to see if all matches in the group you have identified triangulate with each other.  To do this:

• Navigate to the DNA match page with your shared 'match of interest'.
• Click on the first TG icon symbol - this will open up the Chromosome Browser Triangulation Tool;
• 'Add and Remove' matches using the radio button on the top right of the page.
• Only a maximum of 7 matches can be viewed at one time.

If the first segment was quite long, you may find the triangulations are in sub groups, like in the diagram below.  You will need to play around with your match comparisons to identify the subgroups, but eventually you might see this sort of pattern.  (NOTE:  This example is on Chromosome 10, a different  group to the one shared with Ian).

This is demonstrating that whilst everyone is triangulating with 'Match A' (red), they are coming into the group at different levels.  You and 'Match A' share the longest segment, so 'Match A' is probably a closer relation to you and your shared MRCA couple.  The other matches may reflect matches to the same MRCA couple or perhaps a segment belonging to an older ancestor from one of the ancestors in that MRCA ancestral couple.  

If you can identify the MRCA couple for Match A, others in each of sub groups could be segments coming from any of the 4 parents of that couple depending upon whether there was a recombination event in the segment area for Match A.  

For example if Match A (red) was a 2nd cousin, they share your great grandparents.  The subgroups could belong to either of those, or potentially different 2nd great grandparents depending on where recombination events occurred.  Whilst I would initially call this one triangulated group for the entire length of Match A, if you identify the subgroups as belonging to more distant ancestors, you may wish to rename your subgroups as separate TG's.

Read more about reviewing your DNA matches at My Heritage.

Next Steps - the quick way!

After you have mastered identifying your triangulated groups, access the 'My Heritage Auto Clusters' tool under the DNA tools menu.  Click 'Explore' the "Generate' after selecting the kit of interest. Your report will be emailed to you.  When reviewing the report remember that these are shared match clusters and will need to be examined carefully to identify triangulated groups.  

• Check to see if your 'match of interest' or anyone else who appears in your triangulated group appears in the cluster report?;
• Who else is in the cluster?
• Which matches in the cluster are triangulated and who is only a shared match?
• Explore some new groups (optional);
• Don't forget to add any additional analysis to your two master spreadsheet lists 'My Heritage Match List, Total Shared cMs - Kit_IDXXXX'  spreadsheet (Part A) and 'My Heritage Shared DNA file - Kit_IDXXXX' spreadsheet (Part B, Step 1) for future reference.

Unfortunately, the defaults for cluster reports are pre determined by My Heritage and cannot be manipulated.  If no one in your identified TG appears in the cluster report, pick an alternative cluster of interest and apply what you have learnt from the exercise by examining matches in that cluster.

Need more challenges?

Have you identified matches at My Heritage with shared common ancestors on your mystery line?  See if you can identify any triangulated groups on the segments shared with them using the techniques in this exercise.

Veronica Williams

First Published: 3 August 2024

GEDmatch - Exercise to identify triangulated groups and false positive matches.

In Module 2 of  'Organising your DNA data and determining match groups' we discussed ways to organise data and a process for working with My Heritage to identify match groups.  Before moving to Module 3, make sure you understand the theory of segment triangulation and have established a method for retaining records of your DNA research, to avoid rework and improve your productivity.

The purpose of undertaking these exercises is to consolidate your understanding of how to determine triangulated segments, identify potential match groups and whether a match is likely to be a false positive.

In the 2021 and 2023 programs we completed this exercise My Heritage.  Due to temporarily suspension of downloads at many of the DNA sites, the data cannot be sourced for the exercise for the 2024 group.

This modified exercise seeks to use GEDmatch data to practice analysing your matches manually to ensure you appreciate the underlying theory.  Remember, whilst shared matches are 'CLUES' of a shared ancestor, only shared and triangulated segments are 'EVIDENCE' of a common ancestor.

1.  Identifying segments of interest

For this exercise, we are continuing to use the GEDmatch data we collected on our known ancestor match in Module 1, see the previous blogpost.

In my example I identified 3 'segments of interest' with my 'known match', who shared the MCRA of my problematic 2GGP's James Murphy and Elizabeth Bateman.   In the previous exercise if you had other matches who shared segments going back to the target 'ancestral couple', you were advised to repeat the process and also add their shared segments to your spreadsheet.  In my case there were 5 identified matches, but only 4 were on GEDmatch.  After doing 'one on ones' at GEDmatch between the additional three matches and my mother I identified a total of 14 additional segments of interest.

The remaining 'known' match was on My Heritage and shared 3 different segments, however her data has been excluded for the moment.

2.  Identifying matches in the same specific segment locations

Step 1:  First we need to access Tier 1 Tools at GEDmatch, which requires a subscription.   We are going to use the 'Segment Search' report.  This report provides a list of all matches by 'chromosome' and shared 'segment location'.  Run the report using the existing defaults and download the .csv file to your computer.

• Open the 'Segment Search report'.csv file you downloaded from GEDmatch.

• Save it as a separate sheet and give it a working title, i.e. 'Chromosome Analysis - Kit ID GEDmatch'. We will be amending this version, but we also want to retain the original 'Segment Search report'.

• Now we are going to find the areas we identified as 'segments of interest' in Part 1.

• Choose one of your largest segments from the list in Step 1 and find the matching segment location area in the newly created 'Chromosome Analysis - Kit ID GEDmatch' spreadsheet;

• Identify all matches in your list, that match anywhere within the shared segment area of the selected segment of interest.

• Highlight all the matches within the identified segment area.

In the following example I am using the segment on Chromosome 4 that is around 50cMs.  This segment starts at 162.9 and ends at 191.1. 

Step  2:  We will now update the spreadsheet to be able to add additional information as we examine each of the matches throughout the analysis process.

• In your newly created 'Chromosome Analysis - Kit ID GEDmatch' sheet, the columns we will be using will be Match Name 1, Match Name 2, Chromosome, Start Location, End Location, Centimorgans.  

• Delete or hide any unnecessary columns for manageability (optional).  

• You may also wish to format the Centimorgans column to display the numbers showing one decimal point so that it is easier to read (ie 168 is the default number, re-format the column so it would appear as 168.0). 

• Freeze the header row so that you can easily see and sort each column heading later.

• In your newly created 'Chromosome Analysis - Kit ID GEDmatch' sheet, add columns for side (eg P, M, Both, I/F), TG (Triangulated Group), MRCA (Most Recent Common Ancestor) and notes. 

• This spreadsheet will now become your 'master sheet' for GEDmatch data for the relevant Kit_ID.

3.  Identifying triangulated groups within the identified segment location

We are now going to review each match in the identified segment area to determine sides and to identify any triangulated segments, on either side of the chromosome.  

• Firstly, review the data collected from Exercise 3 in Module 1 and transfer the information to the newly created 'Chromosome Analysis - Kit ID GEDmatch' sheet.

• For matches who 'triangulate' with your 'known' match - allocate them to the same side of the family.

• Groups of matches who all triangulated with each other should be allocated a TG number - develop and maintain a system that works for you.  As an example, you could number them as M###, P###, and Side 1_###, Side 2_### if you have not yet identified a side.  In this exercise we know the side so it will be either M### or P###.

• If you know the MRCA (Most Recent Common Ancestor) notate them in the MRCA column;

• Add any notes you think may be useful in the future as you explore matches.

• You may find other close matches from your family in this list, as I did.  In my case, for such a large segment area, there are only limited matches appearing which was surprising.  Each segment area will be different, for every kit.  You may have a few or many matches within the segment area.  If you have a large number, reduce the cMs limit to say >15cMs to make the list more manageable for the exercise.

• Your sheet may now look something like this.

4.  Identifying triangulated groups on the opposing side and false segments

The last part of the exercise is to use the information we have found about our triangulated group to inform us about the 'same segment area' on the 'other side of the chromosome'.  We will next review all the remaining matches who have not been marked to see if we can find matches on the other side of the chromosome and identify potentially false segment matches.

• Firstly check that the match DOES NOT share the segment area with matches identified as belonging to the same side of the 'known' match.  Be sure to check the segment locations carefully, particularly if you are examining a long segment like this one as there can potentially be multiple triangulated segment areas along the length of the chromosome.

• Then run 'people who match 2 kits' and see if there are any shared and triangulated matches on the other side of the chromosome.  If so, in this case they would be marked as 'paternal' and allocated a PXXX TG number.

• If there are still matches appearing in the list, that do not belong to either the 'maternal or 'paternal' triangulated groups, then they must be 'false positives' segments or 'IBS (identical by state)'.  Update your sheet accordingly.

• Remember we can only mark a segment as false when there are triangulated groups in the specific opposing segment locations - on both sides of the chromosome.

• If there is no TG identified on the opposing side, the default position would be to allocate all the remaining matches to the other side for your known match.  Once a TG is identified in this area, the matches should be re-examined and allocated to Maternal, Paternal or False.  Marking segments on both sides as you go, assists with productivity and reduces duplicated effort down the track.  

• Being systematic and methodical will help you in the analysis process. It may seem slow and tedious to start but you will benefit over time.

Next steps:

• The next step in the process is to interrogate each of the matches in the 'triangulated group' (TG) and to aim to push back the segment a further generation by finding a more distant MRCA.  Everyone in the segment 'triangulated group' will share a common ancestor.  The segment could go back many generations, or the match could fit in even closer to you than the identified MRCA, but still shares the more distant MRCA with others.  Our goal is to push back one generation at a time and 'walk back the segment'.

• Even if you cannot identify more MRCAs at this stage, add notes about names and locations that might be useful for further analysis down the track.

• To fully explore all the clues for your ancestor of interest, you should repeat this exercise for all the identified 'segments of interest' identified in Section 1.  Hopefully, more clues will emerge with common surnames or locations between groups.  

• It is not necessary to do all these segments for the purposes of Module 2, just do enough so you are confident with determining TG's on both sides and knowing when it is appropriate to mark some segments as 'false positives'.

• If you are feeling particularly keen to do more and you have other close family tested, repeat all the the steps for the 'known' match with each of them, starting with Exercise 3 in Module 1.  Make sure you consider where the tester sits in the tree and the implications on 'DNA inheritance' when deciding who to examine.  Consider such things as parent/child relationships, if the match is on the maternal side and the mother has tested, there would be no need to examine the child or other descendants as relevant DNA would have already been identified from their mother.  After doing this for my kits for the descendants of the Murphy-Bateman 'ancestral couple', my list of 'segment areas of interest' increased from 14 to 32!

Veronica Williams

First published: 3 August 2024