DNA can be complicated. Even though scientists and genealogy experts are working hard to make this fascinating science more accessible to the general population, sometimes it can still feel more than a bit confusing. Let’s refresh our memories and return to biology basics by revisiting what most of us learned in high school.
In his presentation at RootsTech 2018, Jim Brewster from Family Tree DNA took attendees down memory lane to rediscover biology basics that are helpful when trying to understand how modern DNA testing works. Do you remember the structure of a human cell? After joking that the technical term for cellular content is simply “stuff,” Brewster identified all of that “stuff” on a big screen for attendees. He then talked specifically about the three types of DNA tests available today—Y-DNA, mtDNA, and autosomal DNA—and which parts of the human cell they are related to.
Breaking down DNA
Every human cell contains a nucleus. Inside each nucleus are 23 pairs of chromosomes, which are essentially the blueprint of the body. However, the 23rd set of chromosomes are different; they are sex chromosomes, which determine a person’s sex. Females have two X chromosomes, and males have an X and a Y chromosome. Males can do a Y-DNA test based on their Y chromosome to trace their paternal line from father to father to father.
Also within the cell are the mitochondria, or the powerhouses of the cell. They provide the energy necessary for the cell to operate. Now, the curious thing about mitochondria is that they carry a unique type of DNA only inherited from an individual’s mother. Mitochondrial DNA, or mtDNA, is essentially the opposite of a Y-DNA test: it helps an individual trace their maternal line from mother to mother to mother.
Testing Y-DNA and mtDNA can yield very specific and valuable results. But for those who are looking for cousins or close relatives within the past five or six generations, an autosomal DNA test should do the trick. Autosomal DNA tests are based on the other 22 sets of chromosomes floating around in each of your cells. Scientists working for genetic genealogy companies use this blueprint of your body and compare it to DNA samples collected from other individuals to help you find living relatives. That’s why autosomal DNA tests are generally the most popular kind of DNA test available today. There are a lot of people out there interested in discovering new family connections, especially adoptees!
Weighing the Options
When it comes to deciding which test is right for you, Brewster says that making the choice depends a lot on what you’re trying to learn about your family. When someone asks him what DNA test is best, he likes to share an analogy. “I always think of [it] like walking into a hardware store and saying, ‘All right, I want you to sell me the best tool in your shop.’ Well, the clerk’s probably going to look at you and say, ‘Well, what are you trying to do? … I can sell you the best hammer that I have in my shop, but if your goal is to saw a log in half, that hammer probably isn’t going to do you a whole lot of good. You’re probably going to want a saw.’ Does that mean that a saw is better than a hammer? Well, no, not necessarily. It’s that it’s for different purposes,” Brewster explained.
Brewster explained further, “I always tell people that they should focus on what their goal is. If your goal is to trace the direct father’s line, … if that’s where your brick wall is, if that’s what you’re trying to prove, then a Y-DNA test is the best for you. If you’re trying to get past the brick wall on your direct mother’s line, then an mtDNA test is going to be best. If it’s everything in between, then a Family Finder test is going to be the best for the autosomal.”
This is the first of a three-part series about finding the right DNA test for you.