VISITING THE X-CHROMOSOME

So until now, in the Pikholz DNA Project...
I have looked at the Y (male line) chromosome of some of the Pikholz families and we see that three of the Skalat families have a perfect match to one another at 37 markers. This tells us that these three families have a common ancestor most likely six or seven generations back. (They cannot be closer, as we know the five most recent generations.)

The Y tests also told us that certain other family members do NOT have a male line that matches the rest of us.

We did a MtDNA (female line) test on a member of the one Pikholz family that has only an all-female line. That showed a few good matches with non-Pikholz tests, but nothing good enough to work with.

And we have been looking at autosomal DNA tests, as I have discussed before on several occasions. Those are the twenty-two pairs of non-sex chromosomes. Most of the results have been ambiguous to this point.

The X chromosome
So now I'd like to say a bit about the X chromosome. Men have one, which comes from their mother. Women have two, one from the mother and one from the father. The one a woman gets from her father is the same one he got from his mother, so essentially, women have one from the paternal grandmother and one from the mother.

Genetic genealogist Blaine Bettinger put together these diagrams which show how the X chromosomes of men and woman are made up. (Pink represents female ancestors, blue male.)

The circle in the center is the male. His X is from his mother. She in turn gets from her two parents, who get from his mother and her two parents. And so on. The number of ancestors in each generation increases according to the Fibonacci Sequence.

The percentages in the illustration assume that a woman passes on half from her mother and half from her father. but this has been found to be incorrect, as Roberta Estes demonstrates. The mixture that she passes on from her parents can be 50/50, but it can also be 90/10 or 73/27 or anything else.

On the right we see the female chart from the circle in the center. Her right side is the same as that of a man's, all of it coming from the mother in exactly the same way.

But she also has an X from her father and that is what appears on the left.

Family Tree DNA, the test company our project uses, began to include the X chromosome in its results about a month ago.

(Let me emphasize that the X chromosome is not the same as MtDNA, though both involve the mother.)

The surname that will not go away
The first person I looked at was Mark. He is a non-Pikholz from a Skalat family, who matches many of us, and I wanted to examine his theory that he matches us on his mother's side.

He matches six of us on the X chromosome, in two distinct groups, both of them nearly perfectly overlapping. A seventh match (Micha) overlaps no one else, so I am ignoring that.

In the first group, Mark matches Dalia, Gadi and Robert. Mark's matches with Gadi and Robert appear identical. As it happens, both Gadi and Robert are Rozdolers, but these are X chromosomes, so they would be from their mothers' (non-Pikholz) sides.

The match with Dalia is nearly identical. In her case, the match could come from either her Pikholz father or her non-Pikholz mother. Dalia is a Skalater.

The second group has much smaller colored bits but is much more interesting genealogically. Herb and Betty are first cousins. (Betty is my father's sister.) Their matches with Mark are identical. (I could not appear there because my X is from my mother's side. My second cousin Terry could, but doesn't.)

The third person in this second group, Miriam, is a Rozdoler. Her match cannot be from the Pikholz side, as that would be her father's father's side, and her father received his X from his non-Pikholz mother.

So I looked to see what I know about Miriam's mother's side and it turns out that Miriam's mother's maternal grandmother is Miriam WACHS. Well, we certainly know the name Wachs. That was the family I discussed in my very first blog post.

We know that Herb has Wachs in his ancestral backgound, on his father's side. There is a persistent tradition, confirmed by Wachs descendants from Pittsburgh, that there is some sort of connection between them and my own Pikholz family from Pittsburgh. Unfortunately, no one has a clue what it is.

Mark tells me that his paternal grandfather had a cousin who married a Wachs in Tarnopol, but that shouldn't matter because that Wachs would have no common ancestry with Mark and besides, the connection is on Mark's father's side which doesn't affect the X chromosome.

So I haven't a clue how to resolve this.

Robert
Next, I decided to look at X matches for Pikholz males - generally their non-Pikholz sides. I wanted to see if some of the non-Pikholz who matched many of us did so on our mothers' (non-Pikholz) sides. When I did this for Robert, I find something remarkable. He matched three Pikholz on his mother's side, two of them men, which meant on their mothers' sides as well.

Not only that, but as you can see on the right, those matches overlap with one another.

Note that I had inadvertently set the level of testing to 1 cM (centiMorgan), which would include very small segments, but as you can see, these are not very small segments, so that appeared to be irrelevant. At least that's what I thought.

Since one of the excuses the experts use to explain this kind of thing is that the matching segment is too small to be meaningful, I had a look at the precise sizes. And here there was a surprise. The longish green match between Robert and Dalia turns out to be two nearly adjacent matches, the first 1.52 cM, the second 5.23 cM. Robert's matches with Micha and Gadi are 5.83 cM and 2.16 cM respectively.  The experts say to ignore bits less than 5 cM, so we can ignore Gadi here entirely.

I'm not sure what the close matches among Robert, Micha and Dalia can tell us, but we can certainly see that the size of the colored bits on the chromosome browser is very misleading. Gadi's match with Robert looks to be bigger that Micha's, but in fact it is less than half the size.

Another odd thing here is that Robert Gadi, Dalia and Micha match in the same place as Mark, Gadi and Robert but Micha and matches Mark in a different place on the X chromosome.

So I went back to Mark
The actual numbers for group with the larger colored matches with Mark are Dalia -1.29 cM. Gadi and Robert - 1.41 at exactly the same place. These numbers are supposedly too small to be on interest, but it is hard to ignore the precise overlap of the three men and the near-precise match with Dalia.

The actual numbers of the very small colored segments in Mark's second group are Herb and Aunt Betty 4.65 cM in exactly the same place and Miriam 8.2 cM. Miriam's match with Mark includes the entire segment of A. Betty and Herb. These are much more significant numbers that the ones that appear larger.

Now I have to figure out what to do with them.

But I have a plan 
I really have to learn more about how all of this works and to that end have successfully enrolled* in the week-long Genealogical Research Institute of Pittsburgh course in Practical Genetic Genealogy to be held in July in Pittsburgh.

I am hoping that that experience will make me better equipped to analyze all these test results.

I also hope that the lecturers do not end up saying that Ashkenazi Jewish (what they call AJ) DNA is too difficult to do well, because the population is too deeply inbred.

* Successful enrollment was no small matter. When registration opened last Wednesday at 7 PM my time, they had so many applicants that the server crashed. They were finally up at 7:09 and when I finished submitting my form at 7:12, all I got was a waiting list. But that came through the next morning.

Housekeeping Notes
My interview is now live.