Different Kinds of DNA Analysis

In 2006, I had my DNA analyzed through Ancestry by DNA; results are described in an earlier posting. I am in the process of obtaining results of an analysis done through 23andMe. Plowing through results is helping me understand different kinds of DNA analysis. I’ll post another blog entry or two as I learn more.

DNA is located in two places: in the genes within cell nuclei, and in mitochondria inside the cell but outside the nucleus. In this entry, I explain the difference between two kinds of DNA analysis: BioGeographical Ancestry, and Mitochondrial Ancestry.

All humans share about 99.9% of DNA; only one-tenth of one percent of our DNA makes of different from each other. So when DNA is analyzed for ancestry or anything else, only specific markers are analyzed. BioGeographical analysis works with 176 ancestry informative markers on genes within the cell nucleus, which contain contributions of genetic coding from both parents. These markers can distinguish proportions from four continental ancestral populations: Europeans, West Africans, Indigenous Americans, and East Asians. The theory supporting these four populations holds that as humans migrated out of Africa starting about 200,000 years ago, genetic markers gradually mutated. However, migrations have never stopped, so the genetic make-up of people reflects a history of migrations. Click here for an example of genetic diversity among Germans, including traces of Native American ancestry. 

Once you have established a significant amount of ancestry within one or more of these four broad geographical populations, you can have your DNA further tested for broad ethnic ancestry. These tests operate on the same principle as described above, but look at different ancestry informative markers.

BioGeographical Ancestry is not an exact science. Rather, the results you get represent likelihoods.

Mitochondrial DNA analysis works differently. Mitochondrial DNA, located within the cell but outside the nucleus, is passed down only through the female side of your ancestry. Men have their mother’s mitochondrial DNA in their cells, but in the process of conception, mitochondrial DNA in the sperm is destroyed. Because it doesn’t participate in the mixing process that occurs at conception within cell nuclei, when genetic material from both parents is combined, mitochondrial DNA rarely mutates. Scientists can determine about how many generations ago mutations occurred. About 200,000 years ago, all humans shared the same mitochondrial DNA. But as populations spread, occasionally mutations occurred, creating what are called “haplogroups,” passed down through the maternal line

The video below explains these same concepts, with visual illustrations:

 

I have learned that I belong to haplogroup U3a1. What that means is that if I were able to trace my mother’s mother’s mother, back 45,000 years, I would come to a woman somewhere around the Caucasus mountains, the Balkans, or north Africa, whose mitochondrial DNA mutated, breaking her off from haplogroup R to form haplogroup U. About 32,000 years ago, mutations of U group mitochondrial DNA produced 8 variations of U: U1, U2, U3, you get the picture. A couple more sets of mutations, and the U’s subdivided even further. My haplogroup, U3a1, dates about 4,000 to 7,000 years back, to a mutation that occurred in eastern Europe or the Middle East. People carrying this DNA migrated into Europe, central Asia, the Balkans, and North Africa, today constituting less than 5% of the populations of those areas (with the exception of Roma people, about one third of whom are members of this haplogroup).

Of course, it is important to remember that, since haplogroup is passed down only matrilineally, what I learn from this analysis constitutes only a small fraction of my total genetic make-up. 

Undoubtedly, this is detail about genetics that most readers will get bogged down trying to follow. It has taken me several hours just to sort out and make meaning of this much. But the take-away message is that DNA analysis can help you trace your ancestry, but there is no single DNA test, and different tests tell you about different things. Stay tuned as I learn more.

Comments

  1. Still learning about all this 🙂 Thanks for the blog and the vid 🙂 I am U3a1c, neat to know that somewhere WAY back when we share a common x times great grandmother 🙂

  2. donna anderson says:

    Wow!!! Thanks for breaking this down for us a little more….I have attempted to on several occasions but there is soooo much seemingly conflicting info at times that I literally end up more confused than when I started :/……will look forward to your future findings …thanks again cousin? and GOD BLESS 🙂

  3. Dawn Richardson says:

    Hi I am U3a1 from the European Sub group through my MtDNA.. I am mainly Irish but also have connections to Scotland and born in England.. Descent from Scandinavian/ Dutch/Dane/ Swedish Haplogroup.. Some Polish and Italian going back 7000 years in the Maternal line.

  4. I am Icelandic. I discovered thirty years ago that I was able to trace my matrilinear ancestors back to the 15th century using only published printed sources and that they were for many generations married to the richest and most powerful men in Iceland. I was rather surprised to find that this is my mtDNA and that it is so rare globally and that it is rather rare in Iceland as well.

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