Friday, July 5, 2013

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?


  1. Nice writeup CeCe. I need to get back to testing more of my kinfolk as well. I liked the concept of your chromosome map. It provides me inspiration to do it myself.


  2. You really make a great case here for testing close relatives descended from your 8 great-grandparents and even the 16 great-greats. Thanks.

  3. Wonderful! I really need to start doing this graphically. Where did you find the chromosome chart that you used for your final map? It really is a beautiful representation!

  4. Thank you all for commenting!
    Lisa, I used our editing program (After Effects) and Photoshop. I have been begging for a program for years! Kitty Cooper is working on one now.

  5. Heck, CeCe, I just realized I must have some segments to label from my mother! I have matches with three male McElrea cousins (my mother's maiden name). I've been so interested in connecting them all together, I forgot about charting for my own genome! Kitty will make a lot of people happy with her efforts.


  6. Very nice Cece.. I suggest testing a Moore from the Delaware Valley since my Moore that we connect on is from Delaware or Maryland.

  7. CeCe:
    You never fail to continually surprise me with your knowledge of this subject. I love the use of DNA Mapping and am looking forward to being able to do this with my own matches. Please do forward this newest tool as soon as it is available. So very interesting!

  8. CeCe,

    I understand about gaussian distributions (and such like), but I wonder if some of the variations in reported DNA sharing by 23andme are caused by the threshold filters they establish before they recognize some portion of DNA as being 'shared'.


  9. CeCe:

    Great write up and I love your DNA map. Unfortunely, I do not have family to help compare with since I'm adopted. I was interested in your % of your matches. Makes me wonder about my 23andme results about matches that show as 2nd cousins (the closest I have). Thanks for your blog :) Keep it up