I’m taking Chromosome 20 out of order. This one has been a problem Chromosome in the past in that I have had so many matches. And they have all seemed to triangulate. Blaine Bettinger had a recent poll on Facebook on how many new matches people had at Gedmatch. I had 41, but my largest new match was on Chromosome 20. My previous free-hand mapping showed this:
However, my match spreadsheet seemed indicate I had Hartley DNA at the start of my Chromosome where the new match was:
Putting the Fox Spreadsheet to Work
I start with a blank slate on the Chromosome 20 tab and quickly go to the ‘all cousins’ option at the bottom left. I like this option as I can go from the known to the unknown. I’ll start with the first Hartley cousin on my list – Joyce. This view will immediately point out crossovers for five siblings:
From this, it already appears that I either have no Hartley DNA at the beginning of the Chromosome or very little. Certainly not between 2 and 10M where Jon has Hartley DNA. I have circled crossovers for all siblings except for Lori. Based on my old mapping, Lori had all Frazer DNA on her paternal side of Chromosome 20.
Setting the Crossover Lines
I forgot to do this first. I made some lines, though I may have missed a few and they didn’t all line up perfectly:
Above, I put in orange Hartley above for Joyce’s Hartley matches in blue on the lower half of the image. Then on the other side of the Hartley crossovers, I put in Frazer as that is the only choice on the paternal side. Above and below where there was no Hartley match, I also put in Frazer. I’ve mapped quite a bit of the paternal side already. However, some quality control will be needed.
Maternal Lentz Cousin Carolyn Mapped
Carolyn’s match ends at 56.2M. Jon’s crossover is at about the same place, so I shouldn’t go past that crossover. I’ll add in Rathfelder above and below where there are no Lentz matches:
Next, I’ll carry some of these matches to the left and right based on the crossovers that I have:
Here I have a problem already. Lori is on the bottom row above. She shows a crossover, but no changes in her maternal or paternal side DNA.
Quality Check with the Segment Map
This shows I am off:
I went back and erased the extra maternal DNA I mapped. Then I focused on the sections from V to F:
Obviously the comparisons with Lori (L) in them were wrong. Next, I compared Lori with Joyce and Carolyn at Gedmatch and got this match with Carolyn:
This second match is right at Lori’s crossover: 53.7M. I take that to be more than a coincidence:
This solves the problem at Lori’s crossover.
Next, I’ll extend all siblings over to the right except for Jim and Jon – as they have crossovers to the right:
A glance at the segment map compared to the Gedmatch comparisons seems to show I am on the right track. Then I filled in JIm and Jon based on the Gedmatch comparisons:
Here is the check. It shows that the right side of Chromosome 20 was mapped correctly.
Finishing the Left Hand Side of Chromosome 20
The above represents the right hand side of Chromsome 20 for the six siblings. Next, I can either go with the Gedmatch comparisons or look at more cousin matches. I’ll try cousin matches. Judith is another Lentz relative:
The blue lines don’t line up well, so it is best to look at the match numbers. Judith matches Sharon up to position 6.6M. She matches the others up to 8.4M. That means Sharon has a crossover from Lentz to Rathfelder at 6.6M.
That brings up a potential problem as I had it that Sharon had another crossover between purple and purple. However, as I look at the Gedmatch comparisons again, I see that the Sharon crossover should be a Lori (L) crossover. I’ll change this and try filling in the rest:
I got this far, but didn’t finish filling in Jim (V). He has three crossovers in the blank area and I only have need for two. If all the other segments are right, I can fill in Jim’s missing segments using the Gedmatch comparisons. Now I have it down to here:
[Note: In review, I see that here I should have just carried the Lentz through the first V crossover to the second V crossover. That would have saved time and made the corrections below unneccessary.]
That corresponds with these comparisons:
V&S is FIR, that would put Rathfelder in the narrow segment for Jim. That would mean that Jim (V) has no crossover after L. That gives me this:
Just looking at this, I see a mistake on Lori’s maternal bottom Chromosome 20. She goes from Lentz (green) to purple Rathfelder on Jim’s crossover, so I need to fix that. Next, I’ll do a final quality check:
This shows I still have Jim’s outlined segments wrong. That’s all right, because Jim is the last DNA tested sibling. I want to get his right. By Gedmatch, V-L should be all HIR. I have four no matches and one FIR. I see that there is a problem on the left side of the boxed area. I have green to red and red to green with no transition. There has to be a small HIR between a red no match and a green FIR. The other issue is here:
I show Jim having a double transition with only one transition or crossover line. I know from Jim’s match with Joyce that his crossover should be on the paternal top side. That means that there should not be a maternal change at V above. It also means that I should not have taken out the other Jim (V) crossover.
The Final Answer for Chromosome 20?
These two images below should now agree:
Summary and Conclusions
- I was able to map Chromosome 20 using the Fox Spreadsheet after a few corrections.
- It is easy to make mistakes with all the crossovers and segments.
- Each of the four grandparents are fully covered between the six siblings.
- I (Joel) have a full maternal Chromosome 20 of Lentz and no Rathfelder on Chromosome 20.
- The comparisons don’t always line up visually. You have to look at the actual position numbers.
- I was able to confirm earlier mapping I had done.
- Using the Steven Fox Segment Map helps to correct any mistakes that I may have made.