Known Relative Studies at 23andMe: Second Cousin Comparisons, Allen Great Grandparents

I am very pleased to report that I have received the results for my Allen second cousin's DNA test. This is exciting because he shares the only set of great grandparents from whom I have had no genetic data up to this point. Our common ancestors are our great grandparents George Henry Allen (1880-1965) and Fredrikka Herstad Allen (1871-1953). They were both immigrants to the United States around the turn of the 20th Century. George was from Australia and Fredrikka was from Norway. They met in San Francisco and married shortly after the Great Quake of 1906. I descend on my paternal side through their daughter Wanda and this cousin descends maternally through their daughter Flora.

I was surprised to see how much DNA we all share with our Allen Cousin. My family shares more DNA with him, across the board, than we have with any of the other cousins in my "Second Cousin Studies". My sisters and I share well above the expected percentage for a second cousin of 3.125% of DNA in common with our Allen Cousin: 4.45%, 4.27% and 3.64%.

Three sisters compared to their second cousin

As usual, you can see the unique pattern of inheritance, with each sister sharing different portions of their genome with this cousin (shared DNA with each illustrated by the three different colors).  You an click on the chart to get a closer look. Chromosome #6 is especially interesting because we all share a majority of that chromosome with our cousin, meaning that for all three of us siblings the Chromosome #6 that we inherited from our father was inherited almost exclusively from his mother Wanda and, in turn, his Allen grandparents.  At the same time, we can be confident that our Allen cousin inherited his maternal Chromosome #6 almost entirely from his grandmother Flora and her parents George and Fredrikka. In my experience, it is a bit unusual to see such a large portion of DNA inherited intact over multiple generations such as this, especially by all tested descendants. Conversely, you can see that none of us have inherited any common DNA on Chromosomes #4, 5, 8, 10, 11, 15, 21, 22 or X. That doesn't mean that we didn't inherit any DNA from our Allen great grandparents on those chromosomes, only that we cannot detect any in this comparison due to the lack of shared DNA in those areas. In order to be able to detect the common ancestors' DNA, BOTH sides must inherit the same genetic blocks. If we tested this cousin's siblings, we would, almost certainly, be able to pinpoint more DNA from the Allens in myself and in my close family members.

Next I compared our Allen Cousin against three of his second cousins once removed, children of the sisters in the first chart.

Allen Cousin compared to three 2nd cousins once removed

As you can see they retained much of the common DNA on Chromosome #6, but lost many of the other blocks of DNA that their mothers had in common with the Allen Cousin in the first chart. Overall, they were still on the high sharing side with 2.29%, 2.02% and 1.81% instead of the expected average percentage of 1.563% between second cousins once removed. Below is a closer look at the autosomal DNA inheritance pattern of one of the sisters and her offspring compared to our Allen Cousin.

Our Allen Cousin compared to one sister and her offspring

You can see that most of the DNA in common was retained on Chromosomes #2, 6, 13 and 17, while much was lost on Chromosomes #3, 9, 12, 16 and 18.

Lastly, I compared my aunt and uncle to this cousin. Although they are first cousins once removed, they share so much DNA with him that they would appear to be full first cousins. In fact, that is what 23andMe predicted their relationship to be with 11.8% and 11.1% of their DNA in common. Since first cousins are expected to share an average of 12.5% of their DNA and first cousins once removed are only expected to share approximately 6.25% of their DNA, you can clearly see why 23andMe's software reached this erroneous conclusion.

The chart below illustrates my cousin's DNA in common with my uncle, my aunt and myself.

Allen Cousin compared to two 1st cousins once removed and a 2nd cousin

In contrast to my sisters and I, who are one generation further removed, my aunt and uncle share DNA on almost every chromosome with him. Since I do not have my deceased father's DNA sample at 23andMe, I added myself to the chart to demonstrate the different inheritance patterns of each of the siblings. The areas where I alone share with him (light blue) shows that my father inherited those sections in common with our Allen Cousin, and his siblings did not (dark blue and light green). For instance on Chromosome #3, my father inherited a longer stretch of DNA in common with his Allen Cousin than his siblings did. On the other hand, my father's sister inherited stretches of DNA in common with our cousin on Chromosomes #4 and #22 that we did not. Look again at Chromosome #6. It is interesting to see that my father's siblings also inherited large blocks of DNA in common with our cousin on that chromosomes, however they are not the exact same blocks that my father inherited, which can be seen clearly in the earlier chart from the three sisters' inheritance. My aunt did not inherit the same DNA as her cousin in the center part of her Chromosome #6, while her brothers did.

I love being able to actually "see" DNA from my Allen great grandparents.

George and Fredrikka Allen

Now that I have second cousins from all of my ancestral lines, my next step is to combine the data from each of my second cousin studies to begin to map out my great grandparent's DNA on my chromosomes and those of my close family. Isn't that exciting?

Identifying DNA from Great Grandparents Using Second Cousin Comparisons

My recent visit to my great grandparents' San Francisco homes inspired me to contact my second cousin from that line and ask him to donate some DNA to my series on second cousin studies. To my great pleasure, he readily agreed with no persuasion necessary. Happily, this is a case of someone who isn't the slightest bit concerned about the implications of DNA testing.

I just received an email that his sample was received by 23andMe. This is very exciting because it means that I will now have tested second cousins from all of my ancestral lines and I will be able to identify DNA from each of my four great-grandparent couples in myself and my immediate family. To me that is very meaningful. Those of us who study genealogy have spent countless hours searching for tidbits about our ancestors, attempting to know them better. It is gratifying to not only know they are a part of us, but to be able to specifically see evidence of this inside ourselves.

For example, in Part One of my series on second cousins, I found DNA from great-grandfather Matti Wiita Reini (specific to one great-grandparents since it was a 2nd cousin once removed relationship). Part Two revealed DNA from Daniel and Millie (Travis) Proctor and Part Three showed DNA from Willard and Blanche (Purdy) Moore. Part Four, yet to be written, will reveal DNA from George and Fredrikka (Herstad) Allen.

My plan is to map the DNA from each of these ancestors to the specific spots on my chromosomes that match each of my second cousins. This then tells me specifically which parts of my DNA come from which great-grandparents. In doing so, I hope to answer the question that I was asked last week at my presentation on autosomal DNA testing for genealogy, "So what does all this DNA matching really mean?" and to inspire more genealogists to explore DNA testing for genealogical purposes by demonstrating to them just how meaningful it can be.


[Update: Here is a rough chart of my chromosome map so far.]

The start of my Chromosome Map of the DNA inherited from my great grandparents above and adding in some data from third cousins below (Click to enlarge)

Confirmed another 23andMe cousin today!

Yesterday one of my friends/cousins at 23andMe mentioned a predicted cousin of his who has ancestors from the Gloucestershire area of England. Since my Allen, Rudge, Trotman, Chitts, Hill, Johnson, Fowler, Bailey, Jones and Pullin families are from that area, I checked out his profile. Of the seventeen surnames on his profile, we shared four (Pullin, Allen, Cornell and Gillet), so I sent him a share request.  Sure enough, he matched both of my father's siblings on Chromosome 13 for a 6 cM stretch.

Click on the chart to enlarge and get a closer look

With confirmation of a match, I immediately focused on the Pullins since according to his profile, he had traced them back to Somerset, UK, which isn't too far from where my Rachel Pullin (b. abt. 1781) married William Jones in 1801. Because I was concentrating on them, I completely ignored the fact that he also had mentioned the area of Waterloo, Ontario (Canada).

After looking at "My Tangled Vine" family tree on Ancestry.com, he informed me that Sylvanus Cornell (b. abt. 1752) who emigrated from New York to Waterloo, Ontario in about 1800, is his 4th great grandfather.  Sylvanus and his wife Joannah are also my dad's 4th great grandparents. This makes my dad's siblings and this match 5th cousins, fitting with 23andMe's prediction that they are 7th cousins with a range of 4th - 10th. [Update - Sylvanus is also his 5th great grandfather, making them 5th cousins once removed as well.]

It is difficult to be sure if our Cornell ancestors are responsible for this match since we very well may also have Pullin and Allen ancestors in common. Also, we do not know Joannah's maiden name and the shared DNA could be from her. So, as I have said before, to be 100 percent confident that we have found the correct connection responsible for the shared DNA, we will have to wait and see if we get any other matches on this spot who also have Cornell, Allen or Pullin ancestors.

One especially unique thing about today's match is that we have so many possible connections. He shares Gillet with my maternal side, he shares Cornell with my paternal side and we might even share Pullin and Allen ancestors from the area around Gloucestershire, England. (His 3rd great grandfather is Isaac Allen and so is my dad's. Not sure if it is the same one yet.)  To make it even more interesting, I have previously corresponded with his nephew (the curator of the Sheffield Museum) about family history, he belongs to David Faux's Young Family Project that I have mentioned in this blog here and he has lived for forty years in Sheffield, where my fourth great grandfather Henry Moore lived and is buried, even attending the church that my Moores helped the Cornells to found in Beverley, Ontario two hundred years ago. When you find a connection like this, it makes all the hard work worthwhile!