1. mtDNA is mitochondrial DNA and is passed down from the mother to her sons and daughters. Her daughters will pass this on to her children but her sons will not pass it on to his children. While this may have some uses in genealogy, the water gets very muddy after a couple of generations. For example, I got my mtDNA from my mother as did my sisters. My sister passed this same mtDNA on to her children but I did not pass it on to my children, who got their mtDNA from their mother. So, I have the same mtDNA as my sister’s children but her children and mine do not have the same mtDNA. I see very little use in it for genealogy but it may identify some recent cousins.

      2. atDNA is autosomal DNA and is a combination of DNA from both parents that is passed on to their children. atDNA is sometimes effective in identifying  cousins and other relatives within a few generations but like mtDNA it can get a little muddy after a few generations. atDNA is basically the test most people do with Ancestry.com and others like 23andMe. The name 23andMe is based on the random mix of genes we get from both our parents which is 23 pairs of genes, or chromosomes, from each parent with the 23^rd pair being the “sex” chromosome or “XY” in the case of males and XX in the case of females. The female gets an X from her mother and an X from her father while a male gets an X from his mother and a Y from his father. So, we each inherit 46 chromosomes from our parents but since we inherit them randomly, my set of chromosomes may be a little different than my siblings. This test gives us a lot of information about both parents and Ancestry is continually expanding the type of information such as telling us what traits we may have and what parent we got them from. In my case, I found the traits information to be fairly accurate and interesting but not that genealogically useful. It does give you some insight into what your ancestors may have been like and there is a certain amount of satisfaction in that. Beyond that and identifying third or perhaps fourth cousins, and that can prove valuable, this test is not likely to help you identify more ancient ancestors.

      3. Y-DNA is the male Y Chromosome and is passed down from father to son. It is in my opinion the most effective DNA test one can take for genealogy. The one drawback of course is that women, who do not have Y-DNA, cannot take the test. It is perfect for separating families with the same surname who are not related. It also will identify family lines where an adoption has occurred or where someone in the line has been born out of wedlock, which happened in the past more often than some realize. One question I have seen is how do you know what a male ancestor’s Y-DNA looks like that was born hundreds of years ago. Well, the beauty of Y-DNA is that my Y-DNA, with some minor mutations, looks exactly like the Y-DNA of my Neal ancestor who was born in the late 1600s in Ireland and we don’t have to disturb his sleep to found out. We do have to have a certain amount of tests from today’s descendants, however, otherwise its just another DNA test telling us where our ancestors came from.

      Using my Durham family to illustrate, descendants of Thomas Durham through his sons David Milton Durham and Isaac Durham have matching Y-DNA that has been identified as White Y-DNA. So, if two brothers, David and Isaac had the same Y-DNA, that can only mean it’s the Y-DNA of their father Thomas Durham. It also proves David and Isaac were brothers, as we also know from genealogical records. It can also only mean that Thomas Durham’s father was a White since the Y-DNA has been identified as White Y-DNA.

      Descendants of Mastin Durham, who is known to be a son of John Durham, have the same Y-DNA as Thomas Durham. Therefore, John Durham’s father had to also have been a White. Ordinarily this would mean that Thomas was also a son of John Durham and that is what was initially thought. Additional DNA SNP testing, however, indicates that John and Thomas were closely related but were not father and son. This is based on Thomas Durham having a SNP that Mastin Durham did not have. If they were both sons of John Durham, they both would have all the same SNPs.

      SNPs are basically errors, usually just referred to as mutations, made when cells make a copy of themselves before creating a new cell. They don’t happen that often but when they do, they remain a part of our DNA sequence. SNPs are useful in identifying branches of a family as in this case. It does require a full SNP testing though which can be a little expensive. It was worth it, however, because it showed that Thomas Durham was not a son of John Durham as initially thought. It also helped somewhat in identifying other branches within the White family. We do not have enough tests as yet to identify who Thomas’ father might have been but perhaps someday we will. There is a concerted and dedicated effort on FamilyTree.com to sort out this White family line.