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?" 

Monday, March 20, 2023

What is a 2nd cousin--once removed?


Degree of cousin-hood:

I'm often asked questions like "what is a 2nd cousin--once removed" and "what is a half=cousin?" The answers all have to do with some simple facts about how you are related to the ancestor(s) you share with your cousin. 

  1. The first question you must answer is, how many "g" s are there in the relationship that defines the shared ancestor(s) you have with this cousin?
  2. Are the two of you the same number of generations removed from this shared ancestor?
  3. Do you share a grandparent couple with this individual or do you share only one grandparent in some previous generation?

With the answers to these questions in mind, you are ready to define your relationship with your cousin. 

Question #1 is how many "g" s are there in the relationship that defines the shared ancestor(s) you have with this cousin? The most common shared ancestors would be a pair of grandparents. Note that there is one "g" in this the definition of relationship with the shared ancestor(s). Whether it is grandfather or grandmother or a pair of grandparents, there is a single "g" in the term that defines their relationship. Cousins who share grandparents with you are your 1st cousins.

By now you should have noticed all the "g's" sprinkled throughout my prose above. That is deliberate both to draw you attention to them but also to emphasize that they are present in "grandparents" and well as great-grandparents which I shall get to shortly.

If your shared ancestors with the cousin in question are a pair of great-grandparents, this cousin is your 2nd cousin. After all, your common ancestor(s) share 2 g's in their designation. Likewise, if your shared ancestors with the cousin in question is a set of great-great-grandparents, how may "g's" is that? The more astute of you have already concluded that this makes the cousin in question is your 3rd cousin. This pattern extends as far back in your family tree as your research may take you. Just count the number of "g's" and make sure to include the one in grandparents! 


Cousin's removed

So far, I've been describing cousins who share the same generation in the family that you do. But as you probably have noticed, many of your closest family members are either a generation older or a generation younger than you. The children of your parents' 1st cousins are your 1st cousins one generation removed. In like manner, the children of your own 1st cousins are also described as 1st cousins one generation removed. These relationships are generally expressed as your "1st cousin--once removed" whether the generation is one generation above you or below you in your family tree.

The same logic continues with additional generations. The grandchildren of your parents' 1st cousins can be characterized as your 1st cousin two generations removed. The mirror image of this relationship would be the grandchildren of your own 1st cousins. They would also be characterized as 1st cousins--twice removed. Again, it does not matter whether or no they are two generations above your or below you in your family tree.

In like manner, the children and grandchildren of your parents' 2nd and 3rd cousins can have the tag of "once removed" or "twice removed" added to their descriptors to help define their relationship to you. Again the mirror image also applies to the children and grandchildren of your own 2nd and 3rd cousins, etc. 

While these distinctions may not be necessary for some genealogical studies, often they become important in deciphering relationships based on the amount of shared atDNA (autosomal DNA) shared with a previously unknown individual.


Half cousins

Half-cousins are an extension of the concepts of half-siblings. It occurs when only one half of an ancestral couple is shared by you and your cousin. It can occur at any level of cousin-hood for any number of reasons. For example, if you had a great-grandfather who had 5 children by his first wife and four more by his second, you would be full 2nd cousins with the children with whom you shared a common biological great-grandmother. The children of the other wife would be your half-2nd cousins and would be expected to share about one half as much atDNA as a full 2nd cousin.             

Counting your "g s"

Remember to count the "g" in grandparents when counting the degree of cousin-hood. 


In the chart above, note that You are located in the box to the right in the row next to the bottom. All those represented in the same row to your left, are your same generation cousins. The one on your immediate left is your 1st cousin; the next one is a 2nd cousin; then 3rd cousin; 4th cousin and 5th cousin on the extreme left. In the bottom row (right to left) are possible 1st cousins -- once removed; 2nd cousins -- once removed etc.

So the answer to the question at the beginning of this blog, "what is a 2nd cousin--once removed", generally would be a person positioned 2 boxes to the left and one down from You in the chart above. If that was your answer, you may be giving a hint to your age. That indicates many of your cousins are younger than you. If you are taking this course for AP credit, you probably figured out that the person 2 boxes to the left of You and one row up would also qualify for this designation. If you caught both, congratulations. You well on your way to becoming a genetic genealogist. Humm. That has two "g s". Maybe 3.