The previous article in this series is Introduction To Using GEDmatch.
Now that we know how to do ‘One-to-one’ comparisons at GEDmatch, and the importance of doing triangulation on matching segments, let’s take a look at the ‘One-to-many’ comparison feature available on the GEDmatch website. The ‘One-to-many’ tool will give us a list of our closest DNA matches found on the GEDmatch site.
After we successfully uploaded our Ancestry DNA test results file to GEDmatch, on the GEDmatch home page, we saw two red asterisks next our kit number, along with a message letting us know that our uploaded file had been tokenized but had not completed batch processing. As soon as a file has been tokenized, it is available for use in doing ‘One-to-one’ comparisons, but additional time is needed before the more advanced features of the GEDmatch site can be used.
While the batch processing step can take up to eight weeks to complete, GEDmatch seems to be completing this processing within just a week or two since making recent updates to their site. You will know that your file has completed processing when the asterisks and message no longer appear on your GEDmatch home page.
Once your file has completed batch processing, you will be able to make use of all the free features and tools GEDmatch offers. One of the most useful of these is the ‘One-to-many’ matches tool.
Clicking on the ‘One-to-many’ matches link will bring up the One-to-many comparison page. Enter your kit number in the first box, leaving the other two boxes as they are, and then click the Display Results button at the bottom.
Clicking the Display Results button will take you to a page that looks similar to the following screenshot. It will take a bit of time (up to a few minutes in some cases) for this results screen to come up. If you have waited at least five minutes, and the results screen has still not come up, hit the back button on your browser, re-enter your kit number and click the Display Results button again.
Your results page will contain a list (in table form) of up to 1,500 people who have uploaded their DNA test results to GEDmatch, and match you on at least one portion of your DNA. These matches will be in descending order, from the person who shares the greatest amount of DNA in common with you to the person who shares the least amount of DNA in common with you. Mixed in with the text above the list of matching kit numbers, there are four buttons which can be clicked. What these buttons do will be covered in upcoming posts. For now, I want to focus on the results table.
There is a lot of information presented in the results table, and this can appear overwhelming at first. As I continue this series of posts on using GEDmatch, I will be going through what all this data means. I wanted to provide an introduction to the ‘One-to-many’ tool, however, as we can use these results to begin doing comparisons and adding data to our Genome Mate database.
When you first run the ‘One-to-many’ tool using your own data, all of the kit numbers in your results list will appear with a green background (an example can be seen in the screenshot of my match list shown above). The green background is used to indicate the match is new, and when you first run the tool all the matches are considered new. After a period of several days, the green background will change to a white background, making new matches in the future easy to spot.
As you will see pointed out in bold right above the list of matching kit numbers, generally speaking, in order for a DNA match with another person to be considered likely to be accurate, at least one of the segments shared in common with the other person must be rated at 700 SNPs or greater and also be at least 7 cM in length. While this is a very good general guideline, these numbers can vary a bit and are not set in stone. The key thing to know for now is that all the matches in your results list will have a segment length greater than 7 cM, unless they are marked in pink, as shown.
The SNP rating of a segment length is not shown in the results grid, and is instead shown by doing a ‘One-to-one’ comparison on GEDmatch. When copying our ‘One-to-one’ comparison results to our Genome Mate software, the software will automatically screen out any segment lengths that are rated less than 700 SNPs, unless we specifically tell the Genome Mate software to accept DNA segments rated lower than this. The times when you may want to import smaller segment lengths, and the reasons why, will be covered in a future post.
Those who are familiar with GEDmatch will be aware there is a tool which allows us to run the equivalent of several ‘One-to-one’ comparisons at once, showing us all of the shared segments in common among our one hundred closest matches, and allowing us to import this data into Genome Mate in one step. This tool is called the Triangulation tool. As part of the upgrades GEDmatch is currently doing on it’s website, the Triangulation tool has been hidden until the upgrades are completed. When the Triangulation feature is made available again on the GEDmatch site, I will write a detailed post showing how to use this extremely helpful tool.
Knowing how to do ‘One-to-one’ and ‘One-to-many’ comparisons, and individually importing this data into our Genome Mate software, however, allows us to continue being productive during those times when some of the more advanced tools at the GEDmatch site may not be available. It also gives us a good understanding as to what the Tringulation tool will be showing us in the results screen it outputs. Lastly, periodically checking our ‘One-to-many’ results will alert us to new matches we have (by looking for the kit numbers with green backgrounds), and allow us to bring this new match data into Genome Mate using the ‘One-to-one’ comparison tool.
Between now and the next post in this series, I would encourage you to check to see if your uploaded DNA results file has completed processing at GEDmatch. If it has, run the ‘One-to-many’ comparison tool using your own kit number. Once you have your list of results, begin using the steps covered in the last post (Introduction To Using GEDmatch) to begin importing your closest matches into Genome Mate. I’ve found it works well to keep the ‘One-to-many’ results page in one browser tab/window, and open another browser tab/window to do my ‘One-to-one’ comparisons, as I’m working my way down my ‘One-to-many’ results page, and copying and pasting the ‘One-to-one’ comparison results into Genome Mate.
Prior to importing your actual comparison results data into Genome Mate, be sure to backup your database file and that you have switched from any test profile you’ve created over to your real profile. Try importing the ‘One-to-one’ comparison results of your ten to twenty closest DNA matches from your ‘One-to-many’ results list. When finished, be sure to backup your database file yet again.
If you get stuck or experience any problems while following the steps above, or notice that a screen has changed significantly from what I’ve shown in the screenshots, please let me know by commenting on this thread or sending me an email. Thanks for reading.
The next article in this series is Introduction To Using GEDmatch Part 3 (The People Who Match One Or Both Of 2 Kits Tool).
This article last updated 20 Oct 2014