A Second Cousin Adds to My Chromosome Map and Answers A Nagging Genealogical Question

I was so happy to receive results for a 23andMe kit that I had sent to my second cousin a few weeks ago. I haven't had much opportunity to work on my own research or add to my known cousin studies lately, so it was nice to get a result that not only put to rest a nagging doubt about my genealogy, but gave me a substantial amount of DNA to add to my chromosome map.

Willard and Blanche (Purdy) Moore

These new results were from a male second cousin of mine. Our common ancestors are our great grandparents Willard Moore and Blanche Purdy. Having him test killed two birds with one stone, so to speak. He is related to me on my father's direct paternal line, so he carries the Moore surname. Since my dad has so few Y-DNA matches and only one borderline 33/37 Moore surname match, I have been wanting to "walk up" my Moore ancestral line, testing as I go to make sure that my all of my dad's relatives match as they should.

Through DNA testing, I have already confirmed that my dad and his brother were full siblings, as expected. The nagging doubt sprung from the fact that when I compared the 23andMe results for my female Moore second cousin, we shared much less DNA than expected for that relationship (1.17% versus 3.125%). That held true for comparisons against all of my relatives except for my paternal aunt, so I was looking forward to these new results to confirm that our Moore grandfathers were really full siblings.

Jack and Fred Moore

When I chose who to test with this kit, I looked for someone who was not only related on this line, but carried the Moore surname, so I could confirm that he shared the same usual I2b1 Y-DNA haplogroup subclade as my father. My Moore Cousin #2 fit the bill perfectly.

Fred and Jack with their father Willard

Today I received his results and not only does he carry a Y-chromosome with the I2b1 haplogroup, but he shares 3.84% of my autosomal DNA over 9 segments. Much of this was shared on different segments than my female second cousin on this line (they are first cousins), so it will really enhance my chromosome map. In the chart below, you can see the first Moore 2nd cousin that I compared myself to in the dark blue and the latest one in the light green.

I was surprised how different the DNA is that we share since they are (confirmed) first cousins. Notable is the huge 90 cM segment on Chromosome 2. I have a much smaller segment in common with Cousin #1 on that chromosome, so this new comparison will help to extend that segment to cover a significant amount of my paternal chromosome 2 in addition to adding a smaller segment toward the end of the chromosome.

This was a good reminder of how much autosomal DNA sharing can vary within the acceptable range for a relationship. This concept can also be demonstrated by comparing my sisters and myself against this male Moore second cousin. The amount of DNA that I share with him (in light blue) is approaching double what one of my sisters (in dark blue) shares with him.

Another interesting aspect of this comparison is that I now have a 2nd cousin, a 3rd cousin and a 3rd cousin once removed to compare from this Moore line.

Notice how quickly the amount of DNA shared drops from one level of relationship to another, especially the dramatic drop between 2nd and 3rd cousin. Of course, this is just an example and not necessarily indicative of the expected amount of sharing for these relationships.

Probably the best thing about testing this cousin is that I get to update my chromosome map!

My Chromosomes Mapped to My Ancestors (click to enlarge)

This result really inspires me to send those other kits that I have sitting on my desk out to additional cousins! So, who's next?

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)

Known Relative Studies with 23andMe: More Second Cousin Comparisons

Since my last post on second cousin comparisons at 23andMe was so popular, I have decided to expand on it. Another second cousin of mine recently tested at 23andMe. As a result, I have many more relevant comparisons to share with my readers. This cousin is also from my mother's family, but not on her Finnish side. Our common ancestral couple is Daniel Hewitt and Amelia (Travis) Proctor, my great grandparents. Daniel was born in 1866 in Equality, Illinois and Amelia "Millie" was born in 1870 in Sidney, Iowa.

Again, this is a great example of the random nature of autosomal DNA inheritance. My two sisters share 2.56% and 2.98% of their DNA with our Proctor second cousin, while I only share 1.07% of my DNA with this cousin. (The expected percentage of shared DNA with a second cousin would be an average of 3.125%.) Our unique patterns of inheritance can be clearly seen in the chart below. The long gray bars are representative of the 23 chromosomes and the shorter colored blocks signify the shared DNA between each person tested and our Proctor cousin. (For example, toward the end of Chromosome 1, Sister #1 and Sister #3 share the same small stretch of DNA with our Proctor cousin, but Sister #2 does not share any DNA with this cousin until Chromosome 5.)

Click on chart to enlarge

You can really see here that we inherited very diverse blocks of our Proctor great grandparents' DNA. One of  my sisters inherited almost two and a half times more of this "Proctor" DNA than I did, while my other sister inherited nearly three times more than I did. In fact, 23andMe predicts that we are only third cousins, but correctly predicts both of my sisters' relationships to this second cousin.

From this comparison, it would appear that my sisters ended up with significantly more DNA from our Proctor great grandparents than I did. However, since this chart really just illuminates the shared Proctor DNA with this particular cousin, it could be that my sisters happened to inherit much of the same DNA from Dan and Millie that our cousin did and I inherited almost entirely different blocks. To be sure, I would need to test more cousins descended from these ancestors to see if my comparatively low percentage of sharing continues.

This chart shows how my mother compares to her Proctor first cousin once removed (4.56%) and the DNA inheritance patterns of two of us daughters. You can see that the DNA was passed on quite differently to each with only three small areas of overlap between all three.

The chart below shows that my mother's sister inherited significantly more DNA in common with their Proctor first cousin once removed than my mother did: 4.56% vs. 8.55%.

Based on this, it isn't surprising that my aunt's two daughters in the chart below share much more DNA with this cousin than my sisters and I do (#1 = 4.49% and #2 = 4.69%) and with much larger areas of overlap between the three.

It is always interesting to me to see the inheritance pattern as the DNA is passed through the generations. The following charts demonstrate this with each comparing three successive generations to our Proctor cousin.

Lastly, the third generations in the charts above are second cousins once removed from this Proctor cousin. In the charts below, you can see, once again, that the amounts of common DNA inherited at this level of cousinship vary widely with very little overlap. (The only difference between the following two charts is the dark blue comparisons.)

The percentages of DNA in common for the second cousins once removed in this study were 2.91%, 1.22%, .76% and .33% (expected average = 1.563%). For second cousins, the percentages were 4.69%, 4.49%, 2.98%, 2.56% and 1.07% (expected average = 3.125%).

Dan and Millie Proctor (it's their DNA!)

Known Relative Studies with 23andMe: Second Cousins

I recently received the results for my mother's second cousin. Our common ancestral couple is Matti Yrjanasson Syrjala Wiita (1852-1931) and Justiina Johanssdotter Wiita (1843-1907), both born in Ylistaro, Finland. He descends through their daughter Josefina and my mother and I descend through their son Matti.

I am fortunate to have a number of relatives with whom to compare this cousin. The expected percentage of DNA in common with a known second cousin is 3.125%. He and my mother share 3.27%, while he shares about 3.1% with her sister and 2.77% with their first cousin V.  It is interesting to see in the chart below that each of them inherited mostly unique segments with only a few segments in common. The chart compares my mother in dark blue, my maternal aunt in light green and their first cousin V in light blue to their second cousin (KnownC). All three women have the same familial relationship to him, but due to the random inheritance of autosomal DNA, they each share unique patterns and amounts of DNA with him. Notably, all four only share at one small spot on Chromosome 11.

Click on the chart to enlarge and get a closer look

I am also able to compare our known cousin to descendants of the women above to demonstrate what occurs when the DNA is passed to successive generations. Second cousins once removed would be expected to share half as much DNA as a second cousin (1.563%) and a second cousin twice removed would share half of that (.781%), the same percent as a third cousin. My sisters and I are all second cousins once removed from our known cousin. I share 1.08% and  my sisters share 1.84% and 1.38%. For second cousins twice removed, the actual percentages found in this study are .38%, .73%, .84% and .57%.  Below are four charts comparing our cousin to various family members, demonstrating how the DNA inheritance changes as it is passed down. All of the charts are laid out in the same way - comparing one of the second cousins and then two successive generations. All charts can be enlarged by clicking on them.

Note: On Chromosome #8 there is an unaccounted for small match. This match does not show in any other family member and may be a psuedo-segment

Note: On Chromosome #22 there is an unaccounted for match, This may be from inherited from the paternal side.

 

**Update - In the comments below, Dr. Ann Turner makes an important point about these four charts. She writes, "In addition to showing how shared segments vary in size and position, the multi-generation diagrams also show how the segments are inherited in an all-or-nothing fashion much of the time, especially as the segment size grows shorter. The longer segments naturally have a higher probability of being split by recombination."