There is a certain rhythm about performing visual phasing. I look at the crossovers, then assign siblings to the crossovers and position numbers. Then I look at cousin matches. I check the Segment Map agains the sibling pairs, solve any problems that come up and then solve the chromosome.
It looks like I took Chromosome 20 out of order, so now I’ll look at Chromosome 21
Chromosome 21
Here is my first shot at finding crossovers on this Chromosome:
It is best to ignore small changes in these small chromosomes. That is because the changes are magnified in scale compared to the larger chromosomes. One exception to this is at either end of the chromosome. There may be small changes there that are valid. For example Joel (D) has a crossover near the right end of Chromosome 21.
If I did the crossovers right, Lori will have no crossovers.
The Position Numbers
There are only 7 crossovers for six siblings who have two copies of each Chromosome 21.
Cousin Matches
I am dependent on at least one maternal and one paternal cousin match to solve each chromosome. Scrolling down through the cousin matches that I have in the Fox Spreadsheet, I see I have no cousin matches at all. Now what?
I could go with generic grandparents or look for more cousin matches. I’ll start by looking for more cousin matches.
Martin with Latvian Ancestors
I match Martin who has ancestors from Latvia. My Rathfelder grandfather was from Latvia. That is either a huge coincidence, or Martin matches me on my Rathfelder side. In addition, Martin matches my mother and two of my Rathfelder cousins by DNA at MyHeritage. Here is the DNA match I have with Martin at MyHeritage:
If Martin matches me (Joel) on my Rathfelder side at Chromosome 1 and 3, that would be further evidence that he is a Rathfelder match. I’m convinced already, but I’ll take a look.
On Chromosome 1, I have maternal Rathfelder DNA from about 54 to 202.5M. As expected, my match with Martin is within my Rathfelder area on Chromosome 1:
Here are the position numbers of my match with Martin on Chromosome 21:
Martin also matches my siblings Jon, Jim and Sharon. But does he match them on Chromosome 21?
Here is Jon’s DNA match with Martin:
This is about the same match that I had:
Jim has about the same match. Here is Sharon’s match:
40.1 is near the 39.7M crossover that I had for Sharon. That gives me this:
Looking for a Paternal Cousin
Here, I’ll have to get creative. I went to MyHeritage and found people in common with my sister Heidi and Joyce. One who came up was Brianna. I don’t know exactly how we match, but Brianna has her mom as a Hartley. Further, Brianna, Heidi and Joyce triangulate here:
My Chromosome 3 map shows that Heidi has plenty of Hartley DNA where she can match with Joyce and Brianna on Chromosome 3:
It looks like Jon, Joel and Sharon do also.
Here is the match between Brianna and Heidi:
Here is Jon’s match with Brianna:
I don’t match Brianna on Chromosome 21. Jim has a similar match to Jon.
Sharon has a similar match to Brianna:
Here I see that I don’t have a DNA change for Sharon’s second crossover. For now, I’ll fix that by erasing her DNA after the second S crossover. Lori also does not match Brianna, so she must have Frazer DNA on her paternal side.
This comparison shows my visual phasing to be on track:
Here is what I get:
My Previous Attempt at Chromosome 21
Here is my shot at Chromosome 21 from January 2017:
I was unable to assign the segments. I was able to figure out the maternal and paternal sides. It turns out that the purple was Lentz. Blue was Rathfelder. Green was Hartley and orange was Frazer. I was J in the above chromosome map.
Summary and Conclusions
- As the chromosomes get small, there are fewer crossovers, but also fewer cousin matches
- I had to get creative to find maternal and paternal cousin matches. I didn’t have the genealogy to connect these cousins, but the DNA showed which line they were on. Actually, there was limited genealogy. Martin had a tree up to his Latvian father and Brianna had a tree up to her Hartley mother.
- I have full coverage for all four grandparents on this Chromosome.
- Jon has a full Hartley Chromosome 21. Jim has a full Rathfelder Chromosome. Lori has a full Frazer and Lentz Chromosome. Heidi also has a full Lentz Chromosome.
- With this information, it is easy to fill in the match spreadsheets for each sibling. I have a column for grandparent. So I will know for every match which grandparent side they match on.