The previous article in this series is Using GEDmatch Part 5 (Alternate To Triangulation Tool).
Twice within the past week, I’ve come across situations where the GEDmatch phasing tool would be very likely to help solve someone’s genealogical mystery. It seems some people may not be aware of this extremely useful, yet easy to use, tool. Therefore, I thought it would be a good idea to write a few words explaining a bit about what the phasing tool does, and what the benefits of using it are, as well as show the very quick and simple steps to using the tool.
The basics of the phasing tool are that it will take the test results of a child and one, or both, of their parents, and create two GEDmatch test kits. One of these test kits will be just the mother’s DNA, and the other will be just the father’s DNA. Using these two test kits for doing comparisons has a couple of advantages.
The most obvious of these advantages is that in cases where you are only able to test a child and one parent, the test of the other parent can be extrapolated and simulated. This simulated (phased) kit then acts as a substitute in running the available tools on GEDmatch, including one to one and one to many comparisons. While the phased test kits that are created are the most accurate when the tests of a child and both parents are available, the accuracy is reduced only slightly when just the test of a child and one parent are available. In cases of adoption, or non-paternity events, the phased kit can then used to search for matches to help with identifying the unknown parent.
Some words of caution: Please exercise appropriate care and discretion in either of these situations. The revelation of information related to either of these events can potentially have devastating effects. There are people who may prefer not to know about such a situation having taken place, or do not want it to be brought up. Be sure to respect the wishes and privacy of others at all times during your searches.
In cases where the child and both parents have tested, generating phased kits has the advantage of noticeably increasing the confidence level that a shared segment with someone is indeed a valid match, and not just a match by random chance or a false positive, when using the GEDmatch tools with your phased kits.
Click here if you’d like to open the GEDmatch website in a new window/tab to make it easier to follow along with these steps.
Prior to using the phasing tool, a GEDmatch profile needs to be setup, and have the test results of a child, and one or both parents, already uploaded. If you have not done this yet, and need help with doing so, please see my previous blog post Introduction To Using GEDmatch.
1) To use the phasing tool, log in to GEDmatch and click on the ‘Phasing link in the white DNA Raw Data box inside the darker blue Analyze Your Data box in the lower right of the page.
2) Clicking on the Phasing link will take you to the GEDmatch.Com Phased data generator Data entry form page. The entry form is pretty straightforward. You need to enter the GEDmatch kit number of the child’s test in the first box, and the GEDmatch kit number of either the mother’s test, or the father’s test, or both, in the corresponding box/boxes. Once you have finished entering the kit numbers, click on the Submit button.
3) That’s all there is to generating the request to create the two phased test kits. You will see a notice about allowing for processing time for the kits to be created. While this process used to take up to eight weeks to complete, the process is now completing in about two days time. When you return to your GEDmatch home page, you will see that the request has been generated, as indicated by the two test kits that have red asterisks in front of them, and begin with the letter P (for phased) in the kit number. One kit will end with M1, and the other with P1. These are indicating the maternal kit and paternal kit, respectively. Between the P and the M1/P1 will be the kit number of the child.
Once the required processing time has completed, the two phased kits will be ready to be used, as indicated by the lack of asterisks before the kit number.
These two phased kits can now be used just as if the child’s biological mother and father had tested and had their test results uploaded to GEDmatch. These two kits will be automatically flagged as research kits only. Research kits can be used with any GEDmatch utility, but they will not be shown in comparison results for other kits. If someone else runs a one to many comparison against their test, for example, these phased kits will not be among the results shown to them. Phased kits are not allowed to be public on GEDmatch, in keeping with the concerns I raised in my words of caution above.
I hope this may help some people break through some of their genealogical brick walls. I’m sure there are other uses for these phased kits that I haven’t yet fully explored (such as the ethnicity and admixture tools), or uses that I haven’t yet discovered. If you come across any, I hope you will please share them here.
If you experience any problems while following these steps, discover any errors I’ve made, or notice that a screen has changed from what I’ve shown in the screenshots, please let me know by commenting on this thread or sending me an email. Thank you.
This article last updated 31 Oct 2014