Having just received the Etne, Norway local history books (bygdebuker) for Christmas, I have spent countless hours looking at my ancestors in them. Naturally I have been trying to think of even more ways to use these books.
An idea that came to me was to look at my Dad’s one-to-many X matches at GEDmatch.com and see if I could find a match where I could follow the lines and connect them to Dad’s maternal grandad via those books
The largest X match he had with an unfamiliar name and email was to *k for 26.8 centimorgans (cMs) and it included a small autosomal match of 6.3 cMs. This seemed promising so I used the user lookup function on my GEDmatch home page and was delighted to see that she had uploaded a GEDCOM.
The GEDCOM number is clickable from the lookup result and it takes you to a page listing the individual. Of course what you really want is the pedigree to quickly scan for relatives in common and there is a button for that at the top of the page. Better is to use the compare 2 GEDCOMs feature from the home page to compare your match’s GEDCOM to your own. Works great if you both have deep trees but I had no luck with that for *k.
Next I clicked on the pedigree button at the top of her individual listing in the GEDCOM which took me to her pedigree page. Nothing jumped out at me and most of them were from Germany.
The X chromosome has always fascinated me. Whether it is trying to track down the family mild blue/green color blindness or just observing X inheritance patterns in my family and others.
The old farm house at Fatland farm, Halsnøy Island, June 2015
This morning I woke up all excited because I realized that a large piece of my X chromosome comes from my Norwegian 4th grandmother Metta Olsdatter Ve (Fatland) born 1729 on farm Fatland, likely in the house pictured here. She died in 1805 on farm Ve (or Wee) so made it into the 1801 census.
So how did I figure this X inheritance out? My Dad and I share 33.5 cMs of the X chromosome with my fourth cousin once removed Maria and her mother (so it is phased). They descend from a different wife of our common ancestor Aamund Bjørnsen Tvetden. So these 3326 SNPs of X located from 68M to 113M must come from him and therefore from his mother Metta.
No I did not share this insight with my husband when he brought me my morning coffee. I know better than to make his eyes glaze over … only other genetic genealogy aficionados would appreciate this, so I am sharing it here instead.
By the way I am still collecting X statistics, so click here for more on that and please contribute yours
Several of the Ve farms, Etne, Hordaland , June 2015
A new approach to problem solving is to appeal to social media. So here is my request to “crowd” collect statistics about X chromosome matches. If you have multiple close family members DNA tested then please help me by filling out this form for each relationship at http://goo.gl/forms/4294xjjhqq
I have already put this request on DNA_NEWBIES and facebook so the form is now, hopefully, well tested and I will list some of my preliminary results at the end of this post. I have to give credit to Blaine Bettinger for this data collection idea; he is collecting autosomal statistics this way, see my post about that and the results so far.
Now why did I decide to collect these statistics aside from my own curiosity? To help an adoptee of course.
The current technology for personal DNA testing shows us the pair of values (A,T, G or C) from each of our parents at every tested position on a chromosome but cannot tell us what we got from which parent. If we could separate the DNA that we inherited from one parent, called phasing, and use that for DNA comparisons then perhaps there would be fewer false matches.
X chromosome diagram – http://ghr.nlm.nih.gov/chromosome/X
Phasing might bring matching segments smaller than 5cM into play. There have been many recent online posts and discussions among leading genetic genealogists about whether those small segment matches are real (IBD) or pseudo matches (IBC). Links to some of those articles are at the end of this article.
The X chromosome is particularly interesting for small segment comparisons because a male only has one of them to go with his Y, so we know all his X DNA is from his mother. Thus it is ‘phased’ to his mother’s results already. Perhaps then smaller matching X segments are more often real for men.
Dr. Kathy Johnston is a retired dermatologist who has been doing genealogical research for over 25 years and genetic genealogy for 10 years. She has been researching the X chromosome since 2008. She recently posted on facebook that small X segments can be IBD so I asked her for a guest post on the subject.
Read on to see what she has to say on this subject.
“My half-sister and I have been tested to confirm half-siblings. Is there any way to know which parent we share” – this is a rephrasing of a question posed by a woman on the DNA-ADOPTION mailing list at Yahoo. A discussion of the problems of mtDNA ensued. Because the mtDNA haplogroups go back thousands of years, a match is no guarantee of a recent ancestor like a mother. So that information can only rule out the maternal side if there is a mismatch. Deeper mtDNA can get closer but still this is not certain territory yet.
However since they are both female, the X chromosome can give a definitive answer because their father(s) would pass his only X chromosome unchanged to each of them. A man has one X and one Y chromosome and a woman has two X chromosomes. Whether the father passes an X or a Y to his child determines its sex, but since neither is recombined the child gets exactly the same X or Y chromosome as the dad has.
Since a girl has two X chromosomes, one is from her dad. Two sisters with the same dad will therefore ALWAYS match on the entire X chromosome since they have one complete X in common. If the mothers are related, then some of their X will be a full match as well. So let’s look at some X chromosome comparisons at GEDmatch:
This is what the two half sisters from the question look like. The blue indicates that there is a match, the colors above it whether on one chromosome (yellow) or both (green), while red is no match. A few small errors can creep in when processing DNA so an occasional little red line can be from an error. Click the read more once you have decided if they have the same mother or the same father.