So, what did it mean?
50.0% shared, 23 segments
23andMe tests autosomal DNA. To break it down as simply as possible (I’m not a scientist and most of what I’ve read about DNA and genetics goes right over my head, so it helps me to keep it simple), the majority of our DNA is autosomal DNA. An autosome refers to numbered chromosomes, as opposed to the sex chromosomes. We all have 22 pairs of autosomes and one pair of sex chromosomes (the X chromosome and the Y chromosome).
The examination of one’s autosomal DNA is highly useful for genealogical purposes. If you share identical segments of DNA with another person, you share a recent common ancestor. The length and number of these identical segments will predict how close the relationship is. The more autosomal DNA that you have in common with another person, the more closely related you are.
A child receives 47-50% of their autosomal DNA from each of their parents, and similarly on average a child receives about 25% of his autosomal DNA from each of his four grandparents. The chromosomes recombine, or mix, as they are passed down from parent to child, so the size of possible shared segments gets successively smaller with each generation.
So check this out:
|50%||Mother, father, siblings|
|25%||Grandfathers, grandmothers, aunts, uncles, half-siblings, double first cousins|
|12.5%||Great-grandparents, first cousins, great-uncles, great-aunts, half-aunts/uncles, half-nephews/nieces|
|6.25%||First cousins once removed, half first cousins|
|3.125%||Second cousins, first cousins twice removed|
|1.563%||Second cousins once removed|
|0.781%||Third cousins, second cousins twice removed|
|0.391%||Third cousins once removed|
|0.0977%||Fourth cousins once removed|
|0.0244||Fifth cousins once removed|
|0.0061%||Sixth cousins once removed|
|0.001525%||Seventh cousins once removed|
(Data from International Society of Genetic Genealogy.)
If you are wading through the vast sea of DNA testing to aid your search, I would recommend reading author and adoptee, Richard Hill‘s website, guide and book, Finding Family. His story is nothing short of amazing. He searched for decades and finally found answers through DNA testing. His results were not at straightforward as mine in the beginning–an adventure for sure. He started his DNA search when the science was just starting to evolve and he followed it through its evolution, using all of the available testing sites and sorting through all of the available information. Mr. Hill has generously compiled all of the useful and invaluable information and has made it available to anyone who is searching. For free.
I spent an entire weekend researching and trying to figure out what “50%, 23 segments” meant (thank you technology and Richard Hill!). I was convinced that the Father that 23andMe found was my biological father. Was he convinced? Not so much.