Genetic Genealogy for Beginners – Chapter 3

 

 

Y-DNA Explained

Almost every article I have read on Genetic Genealogy, there have been comments or reviews from readers stating their frustration and confusion understanding the literature by well intended authors.

This chapter will began to focus on Y-DNA testing, which is the oldest test. Before we get started, lets look at your goals for testing to make sure you are clear. I suggest you write out your goals.

Do you have a general idea or just a curiosity about genetic genealogy or is your focus more specific? Consider the following questions:

  • Are you primarily interested in researching your surname?
  • Are there specific brick walls (you feel you can not  research further) that you wish to target with the use of DNA testing. (African-American getting beyond 1860)
  • How far back in your family tree are these brick walls? (This is a serious question for African-American genealogy researchers.)
  • What is the ancestral pattern back to these walls, i.e. – mother’s mother’s mother’s, mother or father’s mother’s mother’s father’s, father’s father’s father?
  • Are you ready for a long-time project or do you desire quick answers? (Long-time projects are best suited for this type of work. Quick answers tend to create mistake after mistake.)
  • Are there adoptions in your family tree that you would like to explore. (this is another heavy one for African-Americans. A lot of slaves could not read, write or speak English clearly who became free after the Civil War down south and north as well. Many migrated North and West looking for work and places for their families leaving their children with friends, neighbors or just disappearing under unusual circumstances. The people that kept theses children change their names or adopted them unofficially. Example: John Wilson and his family on the plantation may have changed to Amos Myatt and family. The DNA did not change. Understanding this and working through this is a challenge to any African-American researcher. This takes a real slow process of researching and genealogical detective work to find the connection.
  • Is your primary interest receiving a percentage breakdown of your ancestral origins or “Ethnicity”?

Currently there are tests geared at isolating types of DNA that can address these questions and others. They are the Y-chromosome DNA (Y-DNA), mitochondrial DNA (mtDNA) and the autosomal DNA (atDNA). Y-DNA has been in use the longest and has the best track record for helping genealogists demolish those proverbial brick walls.

Y-DNA refers to the DNA found on the Y chromosome. Only males inherit the Y chromosome, so this test can only be used to trace the direct paternal line. A father inherits his Y chromosome from his father who inherits it from his father who inherits it from his father and on and on. Ancient origins of a person’s direct paternal line.

Example from Ancestry.com DNA test results my line. Johns’ family paternal line.

Unlike all other chromosomes, the Y chromosome does not undergo extensive recombination before it is passed down to the next generation. There can be some recombination between the two tips of the Y and X chromosomes, but those regions are not used for genetic genealogy.

 

The unique inheritance pattern of Y-DNA offers both advantages and limitations when applying test results to a genealogical problem. The lack of recombination means that the same Y-DNA footprint is passed down for many generations, allowing a line to be traced many generations back in time. The fact that the same Y-DNA footprint is passed down for many generations is a major advantage when trying to determine if a patrillineal line was a specific biogeographical origin, such as African or Native American. The origin-identifying markers will not be diluted by recombination and will persist through all generations.

Types of Y-DNA Testing

There are two main types of Y-DNA testing for genetic genealogy: Short Tandem Repeat (STRand Single Nucleotide Polymorphism (SNP).  

These test look at different kinds a markers, provide different information, and have different uses and limitations. I will take up more on this subject in the intermediate and advanced chapters at  later time.

 

 

 

 

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