DNA and something called Phasing – 1 Parent

Had this question yesterday, “I uploaded my fathers raw data to GEDmatch. Now how do we do the phasing if I don’t have my mothers DNA?”

Phasing “is the process of trying to determine which DNA came from the mother, and which came from the father. The term is usually applied to types of DNA that recombine, such as autosomal DNA or the X-chromosome. The benefit of phasing is being able to identify which ancestor a segment was inherited from.” http://isogg.org/wiki/Phasing

This particular client’s mother passed away and he has no way of identifying her specific DNA. To get into this more, you might ask, “can’t you just send in some hair from a brush she used?” Why yes you can, IF you can find a hair with a root still attached AND you have blocks of gold lying around the house. This kind of testing is not practical for the average Genealogist.

When you work with DNA you might say generally, “I inherited this much from my dad – say 50% and this much from my mom – say 50%.” Which is kind of sort of a ball park figure. This goes along with what I explained in another blog Why DNA?  My brother, Sister and I all get 50% from our parents. If this were exactly true then we would all be clones of our parents with no perceivable difference. But there are perceivable differences. The differences are all over the place too. So no, you can’t just say I got 50% from each parent and be done with it. Nature has a sense of humor.

So how to tell which parent gave us which parts of our DNA?

Phasing will tell us.

You can not do this currently (April of 2016) at the place where you got your test done, since none of the testing companies offer a phasing tool.

There are two tools available from Genetic Genelogists for Phasing when you have both parents raw data. You can find this information on the ISSOG page on Phasing. http://isogg.org/wiki/Phasing#Phasing_tools

What we want to do is find out which parent we received our DNA from when we only have one parent.

T. Whit Athey, explains how to do phasing when “a family group, consisting of at least three, siblings and at least one parent. The process works best if data for four or more siblings is available.” Phasing the Chromosomes of a Family Group When One Parent is Missing, Journal of Genetic Genealogy, Fall 2010, Vol. 6, Number 1, http://www.jogg.info/62/files/Athey.pdf

We don’t have a whole slew of family members to test to work on this kind of phasing. So, we turn to GEDmatch, https://www.gedmatch.com . If you haven’t already uploaded your raw DNA data to GEDmatch, and at least one parents raw DNA data to GEDmatch, then you will need to do this. Click on upload raw data for your particular company to see what you need to do.

Now that you and your one parent’s raw DNA data is up and available to work with (usually 24-48 hours after initial upload) here is what to do.

Sign in to GEDmatch.
Go to the Analyze your DNA section,
Then to the DNA Raw Data section, and
Click on “Phasing”. This will take you to the “Phased data generator, Data entry form”
Enter the child’s (your) kit number
Enter either the Fathers or Mother’s Kit number
Then Click the link to generate the phased results.

How long did it take? Phasing took 0.45905 seconds.

Child’s Kit: A000001
Father’s Kit: M111111
Processing without mother’s kit.

Paternal kit number: PA000001P1

Maternal kit number: PA000001M1

Your phased Paternal and Maternal files have been generated.

These numbers will appear on your GEDmatch profile page along with other kits you manage. The phased kits will be available for use in one-to-one comparisons immediately. You will have to wait for the usual 24 to 48 before you can compare the new phased Parental kits with other tools offered by GEDmatch.

2 thoughts on “DNA and something called Phasing – 1 Parent”

  1. Lets say both of your parents have passed away. Your half brother has uploaded as have you to GenMatch. Can you do a phasing on the two of you if you are both Maternal to find Possible Paternal? If you can do this ( Although it will not be completely Accurate how can you select your Brother on the Maternal when it doe not give you that choice?

    1. Half Borther and phasing on the maternal side…You can’t really do phasing unless your parent is alive. You could use the GEDmatch Phasing tool if you had one or both parents. Which is what I did since my Mother has passed.

      You could look at shared segments that you and your half brother share to try and find only matches who match you both. It’s not phasing but close.

      There is also a Tier1 GEDmatch tool, Lazarus, you could use to find your Parental associate cousins.

      Good Luck!

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