Monday, April 17, 2023

Converting BIG Y "Private Variants" into "Named Variants" and possibly getting new terminal ySNPs

If you have taken a BIG Y test to explore and identify your patrilineal descent back into prehistory, you are among the pioneers of the latest wave in genetic genealogy. However, you may be able to learn even more about your line of descent in genealogical times. Chances are that your test results identified some "Private Variants." These are variants which so far have only been identified in one man. As soon as they are identified in others they will become "Named Variants". in the process it is possible that your own terminal ySNP will be named and thus extend your trail to your true "genetic coat of arms."

My cousin is shown to have 2 Private Variants

There are two ways to respond. The passive way is to wait until another person is tested who also is found to share these variants. The more assertive way is to identify another man who is likely to share these variants and ask him to test.


In the case of the cousin whose private variants are shown above, we are currently evaluating whether to test his son or his nephew when the next DNA test sale rolls around.


I recently extended my own terminal ySNP by testing my grandson and then my son as I described in two earlier blog posts:

DNA Testing your descendants with BIG Y

DNA Testing your DESCENDANTS with BIG Y 700--Part 2

In those posts I described that we discovered my grandson was only a 110/111 ySTR match with me. Subsequently, we found that my son was a 111/111 ySTR match with me but he also had one mismatch with his son. So my grandson was the ySTR mutant!  


When it came to our ySNP analyses, my grandson confirmed my 2 "Private Variants" but showed one of his own. In so doing one of the previously private variants became the new terminal ySNP for me. After my son tested, he confirmed my grandson's private variant, and by so doing, uncovered a new terminal ySNP that is shared by my son, grandson but not by me. So none of us currently have private variants but we have two new terminal ySNPs--one shared by all three of us and one only shared by my son and grandson and not by me.


I am advised by Paul Maier, a population geneticist who works for FTDNA that the ySNP shared only by my son and grandson had multiple possibilities as to when it was created:


Regarding your son's mutation of R-FTC50269, what we can say for certain is that it's absent from your somatic cells (e.g., cheek cells from your swab).


The mutation could have occurred:

  1. In your reproductive stem cells (spermalogonia), early during your fetal developing; those cells made the sperm cell that led to your son;
  2. In one of your sperm cells later on (after puberty);
  3. Early in the fetal development of your son, such that both his somatic and reproductive cells inherited the mutation. 

But of course, you and your son only tested cheek cells, making it difficult to know for sure which (1, 2, 3) is the case. If you had multiple sons tested and they all shared the mutation, (1) would be most likely.  


In any case, R-FTC50269 would have been created toward the middle of the 20th century and certainly within the Genealogical Era. What will you find if you explore your "Private Variants?" 

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