Comparing DNA using GEDmatch

This is a basic overview of GEDmatch.

Lately, I’ve been evaluating DNA matches using visualization tools on GEDmatch. Fortunately, I worked in cytogenetics for several years, so I was able to learn the tools available for matching DNA segments at the chromosome level.

The example below displays my DNA heritage mapped to each chromosome.

Admixture Heritage and Chromosome Painting

Eurogenes EUtest V2 K15
Chromosome painting and DNA origins. Pink shows my Native American heritage. Red shows English/Irish. Light green shows Eastern European. (GEDmatch: Eurogenes EUtest V2 K15)

What is GEDmatch?

GEDmatch provides DNA and genealogical analysis tools for amateur and professional researchers and genealogists. DNA matching and visualization tools are free to use.

Example of DNA matches on the same location on the Q-arm of chromosome 17. Each number is a different user matching to my DNA. The pink color indicates that the DNA segment match is <5 centimorgans. The tan vertical line shows the location of the centromere.

DNA segment matches on chromosome 17
DNA segment matches on chromosome 17 – Scandinavian relatives

The DNA matches at the same location indicate that these individuals probably share a common relative. Longer segments are typically associated with closer relatives. See the next example.

DNA match with my daughter and a 4th cousin. The DNA confirmed the paper trail.

Chr16 Madelaine and Christopher
Chromosome 16 – DNA segment match with my daughter Madelaine and 4th cousin Christopher. The DNA match spans the centromere.

Uploading your DNA data to GEDmatch

After you have your DNA tested, by AncestryDNA, 23andme, FamilyTreeDNA or another service, then you can upload the raw DNA file to GEDmatch – at no cost. Then you can use various analysis tools to discover more about your ethnicity and find matches to cousins (who used different testing services).

Getting started…

First, register as a GEDmatch user. Next, upload your raw DNA file. Wait a few days for the database to be updated. Start using the online tools to compare your DNA to others.

Register as a new user

GEDmatch is at https://www.gedmatch.com

Registration requires your name, email and a password of your choice.

Click HERE to register.

Upload the raw DNA file.

First, you must download the raw DNA file from the testing company. This is a free service, but can take a little time since the file is large. Next, you will upload the zipped raw DNA data file to GEDmatch. See links below.

Raw DNA file Uploads
Generic Upload FAST
23andMe fast & easy
Do NOT open or un-zip raw
DNA data files before uploading.

GEDmatch Tools for comparing DNA matches

After a couple of days of processing, the DNA data will show up in the GEDmatch database. You will be assigned a kit number and can use a generic name if you like (for privacy). Once logged into GEDmatch, you will be able to view DNA matches using the ‘One-to-many’ matches tool.

After selecting people to compare, I like to check to see how closely related we are. So I use the Generations Matrix Comparison. In the chart below are several 4th cousins (yellow) and my daughter (shown in green). MRCA = most recent common ancestor.

Generations Matrix Comparison.
Generations Matrix Comparison. Green indicates close relatives.

A Variety of DNA Comparison Tools

GEDmatch has analysis tools for autosomal DNA comparison, plus visualization of matches using a chromosome browser,  clustering, and compact segment mapper. The phasing and triangulation tools are helpful for advanced users (Phase 1 – $10 monthly fee). There is an easy-to-use tool for checking to see if your parents are related. The Admixture (heritage) tool can be useful for finding out where your relatives came from.

The ‘One-to-one’ compare tool is helpful for verifying a DNA match with a cousin.

DNA match with Chris H on chr16
DNA match with me and my 4th cousin spans 21.1 Centimorgans (blue) on Chromosome 16

A fun tool to try is the 3D Chromosome Browser.

Chromosome 15 - DNA segment matches in 3D
Chromosome 15 – DNA segment matches in 3D

Note how the DNA segments match in the same location on chromosome 15. This was a sample of possible relatives from Scandinavia. This is called a ‘pileup area‘ – where several people share DNA segments associated with common relative, many generations back.

Hunter-Gatherer vs. Farmer

Shows the ancient origins of your ancestors.

Eurogenes Hunter_Gatherer vs. Farmer Admixture Proportions
Eurogenes Hunter_Gatherer vs. Farmer Admixture Proportions

This chart shows that I am mostly hunter-gather, including South American, plus a fraction of pygmy hunter gather. I guess my relatives liked to forage for their food. The Baltic hunter gather is from my mom’s family, who has Czech heritage.

DNA Segment Mapper

Try mapping DNA of cousins using the compact segment mapper. The results below display 12 relatives matching my DNA on 22 chromosomes (excluding X, Y). Longer segments indicate more shared DNA.

Dark Blue is my mom, and light blue is my daughter. Red is my great-uncle and orange is his son — my 1st cousin 1x removed.

Compact mapper
Compact mapper – showing matching DNA segments by chromosome

Learning to use GEDmatch

Some tools on GEDmatch are easy to use, like finding DNA matches or predicting if your parents are related. Other tools are complex and take some time to understand. Fortunately there are online tutorials and YouTube videos to help.

The Take Away Message…

Once you have your DNA tested, please upload the raw DNA file to GEDmatch. It’s free, fun to use, and will help you discover new cousins and information about your origins.

Have fun.

Tim Knight

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