Adventures in Genealogy DNA Testing, Part 2

DNA and genealogyA few months back, I ordered a 37-marker kit for my dad from Family Tree DNA, who had purchased the company that done our Combs surname study (see part 1). I was offered a special price because of the buyout, and couldn’t pass it up. Family Tree DNA offers 12-, 25-, 37-, 67- and 111-allele tests. Its 37-allele Y-DNA test was the closest I could get in volume to the 43-marker test the Combs DNA study used. I didn’t know which alleles would be tested and I didn’t want to spend a lot of money on a test if the results would not help the study. Besides Family Tree DNA, I could have tested with Ancestry DNA or 23 and Me.

Family Tree DNA sent my dad a test kit within a few weeks. Each kit is for a single test and includes everything in it you need to complete and ship your sample back. It’s a simple cheek-scrape kit, similar to the one I used in college when I learned how to test DNA. Hint: A good scrape of the cheek leads to lots of DNA, which is a good thing for testing. To get a good scrape, be sure to brush the area well with the swab and follow the directions on the package.

In the lab, the DNA is isolated and then goes through a process of DNA replication, either through polymerase chain reaction (PCR), or restriction fragment length polymorphism (RFLP). I haven’t been able to find out which one this lab used (because I am quirky and like the science), so I won’t go into detail here about the process. What’s important is that the lab took the many copies of the DNA and told me what my father’s results were at those allele sites.

For example, let’s say you got the following result: marker DYS393, value 13. Let’s go through what each of those numbers and letters mean on the marker.

  • D = DNA
  • Y = Y chromosome
  • S = a unique segment
  • 393 = identifying number for the unique segment
  • Value = how many times that marker repeats

In this example, the DNA from the Y chromosome on segment 393 repeats 13 times. Got it? There are other numbers and letters, but let’s keep things simple for now. Just realize that every marker tested, or short tandem repeat (STR), is a unique sequence that’s repeated many times.

When I had the results for the initial round of testing, I immediately got in touch with the DNA study administrator. She was as eager as I was to match my dad into an already tested line. I had only 27 of the markers this study uses, but it was a good start. Thankfully, I could order all but one of the markers I needed al-a-carte from FTDNA. The waiting game for results starts all over again.

Initially, it looks like my Combs family line might be from a line that originates in Dorset, England. We can’t say for sure, however, and I hesitate to draw any real conclusions based on this information. My dad might have some large value differences in his markers compared to the three samples we have from this lineage.

While we wait for the next round of testing, I’m digging into land, probate and tax records to try to find out who my ancestor Charles Combs’ parents were. One Combs family website points to the possibility that he’s the son of a William and Sarah Combs who moved from Virginia to Surry County, North Carolina. William is listed as dying about 1800, when Charles would have been a young boy around 7 years old. This leads to more questions than answers at this point. Where did they come from? Where is their land? Are they related to any of the Combses already in the area?

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