Analyzing Chromosome 15 of a James Frazer Line Family

This is part of the Frazer DNA Project. For those descending from 2 brothers who were in North Roscommon in the early 1700’s. The younger brother was James and the older was Archibald. Joanna has 2 of her siblings tested for autosomal DNA. That means we should be able to figure from which of her 4 grandparents most or all of her family’s DNA comes from. This is using a methodology developed by Kathy Johnston. I previously looked at Joanna’s family’s Chromosome 22 in How a Maternal DNA Match May Shed Light On a Paternal Match. These Chromosomes were chosen for 2 reasons:

  1. They are Chromosomes where Joanna recently got a known relative’s matches on one of her non-Frazer grandparent’s side.
  2. They are Chromosomes where there were already matches in the Frazer DNA Project to at least one known Frazer relaive.

Rather than do this analysis and email the results to Joanna, I thought that I would do the analysis in a blog.

Joanna’s Chromosome 15: Three Siblings Compared

First, I go to gedmatch and compare Joanna’s three siblings to each other: Jonathan (1), Janet (2) and Joanna (3).James Line Chr 15

Here green is a Fully Identical Region (HIR), red is no match, and yellow is a Half Identical Region (HIR). Janet and Joanna match as a HIR for the whole length of Chromosome 15 That means they will share one granparent’s DNA for the whole Chromosome 15. Next I add the crossover points for all 3 and assign one person to each. This is the person that appears in 2 out of 3 of the crossovers. Well, here is something I haven’t run into before. All the crossovers belong to Jonathan (1):James Line Chr 15 Crossovers

There are 3 crossover points. They are between Jonathan and Janet and Jonathan and Joanna. The one in common with those crossover comparisons is Jonathan. That is complementary to the fact that there are no crossovers in the comparison between Janet and Joanna. Next we change this comparison into a Chromosome 15 map where we will look at the 4 grandparents that contributed DNA to this family. The 1, 2, and 3 below on the left stand for Jonathan, Janet, and Joanna. Jonathan and Janet have an FIR in the first segment. That means that they both got the same DNA from the same 2 grandparents – one on each side of the maternal/paternal split. That split is represented by the horizontal line between the 2 colors. So for Jonathan’s Line 1 and Janet’s Line 2 we add two colors representing these same 2 grandparents’ DNA that Jonathan and Janet inherited:

JL Chr 15 Seg 1

Jonathan has all the crossovers here. Janet and Joanna don’t have any. The crossovers are where the grandparents change. As Janet has no change (crossover), we’ll say she got her DNA from the same 2 grandparents along her whole Chromosome 15. Then I added numbers at the bottom. These are where the matches start and stop (rounded to the nearest million) between the 3 siblings as shown in the gedmatch comparisons above:JL Chr 15 Seg 2

Joanna (3) will be feeling left out by now, so let’s see what we can do. Janet and Joanna have that HIR that we talked about. That means they will match on one grandparent and not the other. Let’s pick one for them to match. It doesn’t matter whether it is the green or blue grandparent at this point, because the colors are only relative now and not locked in. I pick green as their match and purple will be the grandparent that Joanna has that doesn’t match Janet’s blue DNA-contributing grandparent. All these decisions!

JL Chr 15 Seg 3

Now we can try to fill Jonathan in. This should be easy:

  • Jonathan and Joanna have no match in segment 2 and 4
  • Jonathan and Janet have no match in segment 3

Joanna and Janet both have green grandparents the whole way. For Jonathan to not match them in all those places, there has to be a different color. I have been using orange for the 4th color representing the 4th grandparent’s DNA.

JL Chr 15 Seg 4

Next, I said that Jonathan and Joanna (1 & 3) have no match in the second and fourth segments. The non-purple in the lower half is blue. Jonathan and Janet are non-blue in the 3rd segment as they don’t match, so that is purple.

JL Chr 15 Seg 5

And that was probably the easiest chromosome I’ve ever looked at! Now to add real life actual grandparents. The new matches that Joanna’s family got in were with their maternal grandmother – Miriam Williams. Jonathan matched her, but Joanna and Janet did not. This match rounded in millions is between 90 and 97. I like how gedmatch has the commas; it makes life easier.

Jonathan match William Chr 15

This is on the right side of the Chromosome 15 segment map. I will say that Grandmother Williams is orange, as that is the one that is different from the 2 sisters on the right. Next we will look at Frazer DNA Project matches that Joanna’s family has. I have good matches and sketchy ones that are small.

Chr 15 matches

We decided above that Williams (Maternal Grandmother) should be orange on the top of the maternal/paternal split. That means that Frazer (Paternal side) will be below that maternal/paternal split line. Janet and Joanna have a large Frazer match on the right hand region, so that would be – uh oh, it looks like I made a mistake. Note in the above spreadsheet that Joanna and Janet both have large matches with BZ. BZ is a Frazer (paternal grandfather) relative. The only places that Joanna and Janet (2 & 3) can have the same grandparent (color) on the right hand side last segment is at the green location. That boots Granny Williams down to blue.

JL Chr 15 Seg 6

Where Did I Go Wrong?

I went wrong above when I assigned Miriam to orange. This was based on Jonathan having a match with a Miriam relative and Janet (2) having no match with that same relative. I did have a little qualm about doing this but reasoned thusly: “If Jonathan had a match and Janet didn’t, then it had to be orange.” Also why wouldn’t Janet have a Williams relative match? She has all that blue area to match. So I’ll have to take note not to make that assumption again. I suppose it’s one of those situations where absence of proof is not proof of absence. Fortunately, the Frazer matches bailed me out of my bad assumption.

Adding the Other Grandparents

JL Chr 15 Seg 7

One More Correction

After coming back to look at this after many months, I see a mistake I made. It was Joanna (3) that had a match with a Williams relative not Jonathan. This version is done in Powerpoint which is easier to use. I now have Joanna at the top and Jonathan at the bottom.


This has to be right. Purple is Joanna’s only unique color in the 90-97 area. And only Joanna had a Williams relative match. Likewise, Joanna and Janet had Frazer matches from 67-92. Green is the only color those two sister have in common in that area.

Summary and Conclusions

  • Powerpoint is a better software for visual phasing
  • It is best to use names for identification, not numbers
  • With just one maternal grandparent and one paternal grandparent, I was able to fill in the missing grandparents.




Leave a Reply

Your email address will not be published. Required fields are marked *