Not too long ago, I was at a car dealer with my wife picking up her new car. I checked my email on my phone and was surprised that I had gotten an email from FTDNA saying that my mom had a new close relative. I checked and it was my first cousin on my mother’s side, Rusty. I have been looking at DNA for quite some time now and have written over 100 Blogs, but this was my first 1st cousin DNA results. As a first cousin Rusty’s DNA matches are comparable to mine on my mother’s side.
Rusty on the Family Tree
Here is the family tree on my mother’s side with those that have had their DNA tested:
Rusty matches on my mother’s side. This includes the Rathfelder (blue), Lentz (yellow) and Nicholson (red) families. As Rusty got different DNA from his mom that my 3 siblings and I got from my mom, he will have some of the same and some different matches with all those that have tested so far.
Rusty’s 1st Cousin Matches
I’ll look at my matches with Rusty first as they are more straightforward than his matches with my mom. At least we are both in the same generation. Rusty matches me at 1,164 cM as reported at Gedmatch which is also on the high side for a first cousin. Here is how my matches with Rusty look like on the FTDNA browser:
By the looks of it, Rusty and I light up about half of the positions of the chromosomes.
Why do Rusty and I match as we do?
I like to look at DNA matches in terms of grandparents. That is because I have tried to map all my ancestral DNA to my four grandparents. For example, here is how I have used a visual method to map to my 4 grandparents on Chromosome 10. I am using Chromosome 10 as it comes up later in this Blog:
I will assume that I did the visual phasing correctly. I have the raw data to check, so it can be corrected later if it isn’t 100% right. My sister Sharon is in the first row, Heidi in the second, I’m in the third row and my brother Jon is in the fourth row. The numbers at the bottom are the rough positions of the crossovers. My siblings and I will match Rusty on the blue and purple segments only (maternal side). Looking back up at the FTDNA browser above for Chromosome 10, it shows that I match Rusty at three segments. It is clear that the third match must be a Rathfelder segment match as a little more than half of my Chromosome 10 is mapped to Rathfelder on the right side.
Let’s see how Rusty matches with me and my siblings on Chromosome 10.
This points out an error in my original visual mapping. Based on these matches with Rusty I should be able to correct my Chromosome Map. First, this shows on the right segment, that Rusty matches me (#4) and not my three siblings. That means that my three siblings will have different DNA than me on the maternal side. Note above that difference is not reflected in my Chromosome Map. I have purple Rathfelder mapped to all my siblings on the maternal side. Previous work that I’ve done has shown that my three siblings have a small Rathfelder match at the right end of this Chromosome and I do not. That match is between 132 and 135M. I take that to mean that my yellow segment match above with Rusty must be on the Lentz side and not the Rathfelder side. So, back to the drawing board.
Checking my laptop, I see that I had done a raw DNA analysis on Chromosome 10 in the past. I went back and checked the raw data and found that I had missed my last maternal crossover. I just added that one in to get this corrected Chromosome 10 Map. The map format below was developed by M MacNeill [email@example.com].
The segment that I had missed was the yellow Lentz portion of DNA to the right of my Chromosome. A few points from comparing the Chromosome Map above to Rusty’s matches with the map:
- Chromosome 10 was heavy on Lentz DNA for me and my 3 siblings (yellow vs. Rathfelder brown)
- As a result, Rusty only matches me and my siblngs on Lentz DNA
- Other Chromosomes would likely yield Rathfelder DNA
- By comparing Rusty matches to my family to all my family’s Chromosome maps, I could create a spotty Chromosome map for Rusty on some chromosomes and a more complete one on others (see below)
- Rusty’s match with me was helpful in finding a crossover I had missed on my Chromosome 10 Map on the maternal side.
A simpler Chromosome (16)
Perhaps this example is clearer. I will show my visual phasing map followed by Rusty’s matches to my siblings:
Unfortunately, the order of my siblings is different in the two representations. I am the only one in the same relative position in both representations. A few observations:
- Rusty’s inherited DNA from his maternal grandparents lined up well with the my family’s inherited DNA on the maternal side.
- Rusty’s matches with me and my siblings confirms the visual mapping that I have done for me and my siblings on Chromosome 10
- Rusty appears to have two large segments of DNA on his maternal side. The larger one on the left is from the Lentz side and the slightly smaller DNA segment on the right side of Chromosome 16 is from our shared Rathfelder side.
- Rusty’s crossover from Lentz to Rathfelder DNA appears to be at the abrupt end of his first bunch of matches to me and my siblings at about 49.7M.
This figure is a likely representation of Rusty’s Chromosome 16 on his mother’s side. That means that any matches he has on Chromosome 16 in the red part before position 49.7M will be on his Lentz side and any matches he has in the yellow part of Chromosome 16 will be on his Rathfelder side.
Rusty’s Aunt Match
According to the ISOGG web page, Rusty should match my mom (his aunt) and my 3 siblings and me as follows:
This is a visual show of how Rusty matches my mom:
He lights up the browser pretty well. At FTDNA he shows a match of 2,085 cM. This is close to what Gedmatch shows at 2,160.6 cM. Both of these matches are over the reported average of 1744 cM for an aunt/nephew relationship.
Rusty and Rathfelder DNA
Rathfelders are difficult to find. So far, I have found one other person that tested at AncestryDNA who I have been able to link up to the Rathfelders. I wrote about that Rathfelder match in two Blogs. Here is a link to the second Blog. As best as I can tell, the person I found has the following link to Rusty and my family:
I find it unusual that a couple would give the same name (Johann Georg) to two of their sons. Also to make life confusing, the father, Hans Jerg, was also known as Johann Georg. The chart above shows the person I found (Astrid) as a 4th cousin to my mom and a 4th cousin, once removed to my second cousin Catherine, my family and 1st cousin Rusty.
A Rathfelder Triangulation Group
Here is how Astrid matches my mom and Rusty on Chromosome 17.
Astrid, my mom and Rusty are in a Triangulation Group as they all match each other at least in the green area above. Assuming I have the genealogy right, this points back to an early Rathfelder ancestor:
This shows that the shared Chromosome 17 DNA came from Hans Jerg Rathfelder and his wife. This couple were among some of the early settlers of Hirschenhof which was a German colony in Latvia.
Rusty’s Lentz and Nicholson DNA
I only have one distant cousin, Al, that matches only on the Lentz line. This person does not match Rusty at standard thresholds, so I’ll be mostly looking at Rusty’s Nicholson DNA shown in red below.
On the chart above, Judy and Joshua descend from the Lentz and Nicholson sides. Joan, Linda, Carolyn and Nigel descend from Nicholsons. That means that any match Rusty has with those on the red lines should be a Nicholson match.
Rusty’s oldest Nicholson dna
Rusty matches my mom and Nigel on Chromosome 1. This represents the DNA he got from John Nicholson who was baptized 1765 and his wife Sarah Staniforth.
The browser above shows Rusty’s DNA match with my mom (#1) and Nigel (#2). My mom and my family had a large match with Nigel. So large, in fact, that some on the ISOGG Facebook Page questioned whether that large match could be possible. Here is my Blog about Nigel. Rusty has a more moderate level DNA match and forms a Triangulation Group between himself, my mom and Nigel.
William Nicholson dna
Our shared ancestor, William Nicholson moved his family from Sheffield England to Philadelphia around 1869. Rusty matches Carolyn, Joan and Linda on quite a few Chromosomes. So if I was to map Rusty’s Chromosomes, wherever he matches these three I would map that DNA back to William Nicholson and his wife Martha Ellis. Here is a typical match that Rusty has with my mom (#1) and Joan (#2):
The green segment on Line 2 represents Rusty’s match with Joan and DNA that he got from William Nicholson and his wife.
Here is an interesting situation where Rusty matches his 2nd cousin once removed Carolyn (#1) for a longer segment (in orange) than his Aunt – my mom (#2):
The green segment is Rusty’s match with Linda (#3). Linda and Carolyn are both cousins on the Nicholson side. What does this mean? Let’s see how Carolyn matches my mom. In the places where she matches my mom, there would be triangulation:
Here, my mom matches Carolyn in the same segments where Rusty matches my mom. That leaves the blank on Line 2 above between the blue and yellow segment. Why doesn’t Rusty match my mom in the blank spot? Note that above and below on Lines 1 and 3 that has to be Nicholson DNA due to those Rusty is matching. Here is how I see it.
My mom got her DNA on her maternal side from her Lentz and Nicholson grandparents. In the area that Rusty doesn’t match her by Nicholson DNA, my mom must have Lentz DNA.
a Closer look at Chromosome 10
Here is a closer look at some of the closer Nicholson and Lentz relationships:
Here is how the DNA tested people above match each other by the numbers on Chromosome 10:
In the above spreadsheet, the three sections in gold are Triangulation Groups.
Summary and Further Study
Well this Blog wore me out a bit, so I’ll stop here. There is quite a bit to a first cousin’s DNA:
- I found that Rusty had above average matches to me and my siblings. In addition, he had above average matches to my mom.
- I looked at how Rusty’s match helped correct an omission I had on my Chromosome 10 Map.
- Based on my maps, it should be easy to tell what maternal grandparent line Rusty’s matches are when they match with those on my family’s Chromosome Maps.
For Further Study
- I may look more into what makes up an Aunt/nephew match with Rusty and my mom.
- I’d like to look at Rusty’s X Chromosome matches.
- Anything else that happens to come up as I’m blogging