DNA for the Genalogist

Like many of you, I’ve been seeing a lot of advertising and marketing about having DNA tests performed for Genealogy purposes. From watching “Forensics Files” and other crime shows, I knew that Mitochondrial DNA was passed from mother to child. Was there more to “Genealogy by DNA” than simply determining maternal ancestors?

I haven’t taken biology or chemistry since college. I’d had the basics of DNA and RNA, but I could not recall too much of it other than the most basic of facts. I decided it was time to go “back to school”. Luckily, the internet has much information readily available and many colleges and universities have made information available.

After studying and reading several sources, I began to see the “big” picture with current human knowledge regarding DNA and Genealogy. My key takeaways:

  • Mitochondrial DNA is passed virtually intact from mother to child in the “X” chromosone
  • Paternal DNA is also passed virtually intact from Father to Son in the “Y” chromosone
  • DNA identically replicates itself with mutations only occurring once in every billion nucleotides
  • When mutations occur there are enough markers to still estimate the “Most Recent Common Ancestor (MRCA)” in terms of number of generations since the separation occurred with high degrees of confidence.

The net sum of this is:

  • Both men and women can take a test to determine their maternal ancestry. The test will use the DNA on their X chromosome to determine maternal lineage.
  • A man can take a test to determine his paternal ancestry. The test will use the DNA on his Y chromosome to determine surname lineage.
  • A women who wishes to determine her paternal ancestry can ask her father, brother, paternal uncle, paternal grandfather, or a male cousin who shares the same paternal lineage to take a test for them
  • It is important to have the oldest members of your family line tested as soon as possible to capture important information before it becomes too late.
  • These tests can be used to verify or refute an ancestral claim.
  • These tests can sometimes yield surprises for reasons like:
    • clerical errors
    • unknown adoptions
        A child may have been adopted at an early age and given the “surname” of the adopting family and the adoption was never officially recorded. Adoptions have been common in every age, i.e.. parents died by disease or war and a relative or parental friend took in the children and raised them with their “surname”; or a daughter had a child out of wedlock and the parents raised it as their own. In early America, new identities were often taken which severed “true” family ties.
    • involuntary or voluntary maternal indiscretion

I see where the Dorsey family is conducting the Dorsey DNA Project. They are using tests conducted by Family Tree DNA to determine the interconnections between the changed surname spellings of Dorsey:


If you check out the Family Tree DNA site you will find that there are over 5500 families performing similar testing. If yours is one of them, then you might want to take your own test and join up with your Maternal or Paternal family.


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