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