Researching your Genetic Genealogy

At a particular point in my researches using traditional approaches, I ran into a brick wall. In going back on my Scottish side, that brick wall was the aftermath of the Jacobite Rebellion in 1745. In going back on my German-Russian side, it was the origins of my ancestors in Germany before they moved to South Russia in the late 1700s. It occurred to me that DNA testing might provide some answers. This was back in 2003 or 2004 or so. Over the years since then, this approach has expanded in surprising ways; even though it is still in what is likely to be its infancy. This area is huge and it can be confusing to the new comer. In the following, I’m going to try to provide some initial guidance to folk who are interested in using this method, as I was, and to give some advice for whatever it might be worth to you.

First, there are three kinds of DNA testing currently employed in the area of genealogy. These are tests on the Y-chromosome (Y-DNA), mitochondrial DNA (M-DNA) and autosomal DNA. Each of these tests are useful (or not) for particular reasons. Obtaining a sample to send to a suitable lab is quite easy. Some labs get you to gather a small amount of saliva in special containers, and then mail them off. Others provide a kit that you use to swab the lining of your mouth (inside either cheek), place the swab in a vial, and send that off in the mail. In either case, you’ll collect two or three samples just in case one turns out bad. Gathering the samples couldn’t be easier.

In the case of a Y-DNA test, the utility comes from the fact that any male receives his copy of the Y-chromosome from his father. By extension, his father received his from his own father; and so on back throughout time. Therefore, by studying unique markers on an individual’s Y-chromosome, information can be obtained about that man’s direct paternal line.

What a Y-chromosome test cannot speak to is an individual’s maternal line. Similarly, since women do not have Y-chromosomes, a Y-DNA test cannot be applied to a woman’s DNA directly. Hence, a woman interested in using Y-DNA testing to track her own paternal line must somehow find a co-operative brother, father, uncle, or other male relative to provide a sample. Also, since the transmission of the Y-chromosome is only through paternity, this testing cannot tell you anything about, for example, your mother’s uncle or your father’s mother. It can only trace your father’s father’s father, and so on. In spite of the fact that you will have some DNA from your father’s mother, and your DNA might be similar to that of your mother’s uncle, none of that goes to your (or any male relative’s) Y-chromosome.

To analyze the maternal line, the appropriate test involves mitochondrial DNA. Now, mitochondria are small “organelles” within each of our cells that provide the machinery for cell metabolism. There are theories about how the mitochondria got there in the first place, but none of that concerns the value of testing the DNA in there for genealogy. Unlike the 23 chromosomes that we humans carry in the nuclei of our cells that got their from our two parents, the DNA inside the mitochondria comes only from our mother. It arrived there from being in the egg that was fertilized to create us; and since that egg was part of our mother at the time of her birth, it was copied from her mother, and so on back in time. So, just like the DNA within the Y-chromosome, which traces our paternity, the DNA in our mitochondria traces our maternity. There is one difference in the transmission of Y-chromosomes and mitochondria though, a son will receive his mother’s M-DNA just like a daughter will. So, an M-DNA test can be applied to a male for a maternity test in a way that a Y-DNA test cannot be applied to a female.

There are limitations to M-DNA testing, just like those for Y-DNA testing. For example, an M-DNA test cannot speak to the relationship to your father’s father’s mother. Anything off the direct maternal line is out of bounds. Another limitation is that the amount of DNA in the mitochondria is quite limited. Hence, there is much less information to work with in M-DNA testing. So the ability of using this form of test to get very precise information about ancestry is limited.

Finally, there is autosomal DNA testing. As I said above, we humans have 23 pairs of chromosomes. Of these, 22 pairs are autosomes and one pair are allosomes. An autosome is a chromosome that does not define the sexual characteristics, male or female, of the individual. The allosomes are the sex chromosomes, either both X-chromosomes in the case of a female or X & Y chromosomes for a male. We have already considered the use of Y-DNA testing for studying the paternal line in genealogical testing. The X-chromosome is less useful for genealogy since this will be a blend of DNA from both parents, so scientists have focussed on the M-DNA, as mentioned. So, the autosomes are just the 22 pairs of chromosomes that are present in every cell nucleus within us and that encode all of our tissues.

Now, since our own autosomal DNA will be a combination of that from both of our parents, and their autosomal DNA a blend of that of their parents, and so on back in time, autosomal DNA testing can fill in the blanks, as it were, between our parents. In other words, autosomal DNA testing can elucidate other family relationships such as what DNA you have that may have come from your mother’s father’s mother, et cetera. Until recently, this form of testing was employed to clarify geographical origins. A typical test might say that one was 1/8th Native American, 1/8th African, and the rest European, or something of this sort. More recently, autosomal testing is being employed to reveal other forms of family relationship.

In this regard, it’s worth noting that our father’s father’s father’s father or our mother’s mother’s mother’s mother or our father’s mother’s father’s mother are not currently alive. In most circumstances, we cannot get samples of their DNA either. This is not always true, unless there’s a lock of great grandmother’s hair somewhere; but let’s ignore that for now. What we can test, and what other living people can test, is their own DNA. Let’s consider a Y-DNA test for the time being. If I test my Y-DNA and place the results in one or more accessible databases, then it stands as a reference point for my paternal line. I’ll get back to some of the details about the markers on Y-DNA in later posts; but for now, assume that the markers on my Y-DNA probably haven’t changed for several hundreds, if not thousands of years. In short, my Y-DNA sample is likely to be almost exactly the same as that of all of my paternal line for tens of generations. There will be other men, living today, quite likely with different surnames who share very similar Y-DNA. If it were identical in almost every marker, chances would be highly likely that we have a common male ancestor not too far back.

Scientists who study such topics have worked out ways of calculating just how likely such a common male ancestral relationship is between two living individuals based on how closely their Y-DNA markers match up. The same is true for M-DNA markers and their matches. In the case of autosomal DNA matches, the language for our relationship is “cousin”. Am I and the person whose DNA matches mine to some extent second cousins or third cousins or whatever? By studying how rapidly snippets of autosomal DNA change from generation to generation, predictions can be computed that would estimate that two people who share some specific block of DNA in common are most likely, say, fourth or fifth cousins.

Again, recall that you will test along with other living human beings and then your results as well as theirs will be placed in one or more searchable databases online. I’ll get down to brass tacks as to how this is done in another post, but for now, consider that your not going to get a direct match to your maternal grandmother’s paternal grandfather. Instead, you’ll see some relationship between yourself and some other descendant of your maternal grandmother’s paternal grandfather who is alive today and who tested their DNA and who made the results accessible.

Here is at once the strength and the weakness of this approach. It is only of value to the extent that your potential relations have also tested and made their results available online. It is rather like having a telephone or a facsimile machine. You can only make calls to other people with phones. Of course, in the case of telephones, lots of people have them. There are at least four numbers I can think of by which you could reach me. But not many people have done extensive DNA testing yet, and of that number, their test results are either limited or inaccessible. So, your DNA can’t call their DNA, as it were.

But this is changing rapidly. Every day, more and more DNA information is tested and incorporated into online databases. So, fear not; even if you don’t find great matches today, wait a while and something will turn up. It’s only a matter of time.

Next post, I’ll plunge deeper into the exotic realm of DNA testing for genealogy.

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