DNA stands for DeoxyriboNucleic Acid. DNA is found in the cells of our body. In simple terms it contains the instructions to build an organism (a person in this case). A gene is a specific instruction. For example you might have a gene that says you have blue eyes or one that says brown hair. These instructions are passed from the parent to the child. A human has 46 chromosomes and inside and each of these chromosomes are about 25 thousand genes. These chromosomes are basically packages of DNA and the 46 are arranged in 23 pairs.
Of these 23 pairs, 22 are matched sets or autosomes. One pair (number 23) is not matched and that is the DNA chromosome that decides if we are male or female. If you are male then your 23rd chromosome contains a Y and an X. If you are a female you have two X’s. Every egg produced by a woman contains an X chromosome that is randomly chosen from one of the two she obtained from her parents (one from dad and one from mom). Every sperm that is produced by a man either contains the X he got from his mother or the Y he got from his father.
Genes are arranged in lines on the chromosome. Think of them as islands. In between all the islands is the water. This water is called junk DNA because it really has no purpose in the general instructions for the body. It is in that junk DNA that we find the STR markers-those numbers on Bob’s DNA tests- that determine relationships. So basically it does not tell you if you are going to be tall or short and it does not tell you if you are going to have blonde hair or brown. The genes do that.
Types of DNA
At this point in time there are four ways to test DNA. The first type is autosomal where all 46 chromosomes (23 pairs) are tested. This is the test used for paternity tests and forensic testing. This DNA is a combination of everything that is passed down from our parents and includes the information that determines our identity and our appearance.
The second type of DNA is Y-DNA. This is the testing of the Y chromosome, the one that a man inherits from his father. This type of testing is typically used in surname projects where individuals compare their DNA to look for relationships. If a common male ancestor is shared by two individuals (or more) then the DNA would be exact or very similar. Mutations due occur so the DNA can have a few changes especially when you are sharing a common ancestor way back in time.
The third type of DNA is X-DNA. Males have one X and females have two. The male gets his X from his mother and the female gets one from each parent. This test is difficult to do because the two X’s or the Y and the X are paired together and they tend to share information which is difficult to separate from the X. This test is generally not used for genealogy.
The final type is mt-DNA or mitochondrial DNA. The other types of DNA are found in the nucleus (the center and brain of the cell) but this type is considered to be non-nuclear as it is still in the cell but outside of the nucleus. It is located in the cells that a mother passes to her children, both male and female. Only females can pass this information onto their children.
How is the DNA test used in genealogy?
Because men are the only ones that have the Y-DNA it tends to passed from father to son as an almost exact copy. It is passed along just as the last name is passed. Scientists have organized types of Y-DNA into 24 (and the list is growing) haplogroups. When two or more people have matches or near matches in a haplogroup it means they share a common ancestor. The problem is that common ancestor may have lived a long time ago. With mt-DNA that common ancestor may have lived several thousand years ago and probably not less that many hundred years ago when compared to a general pool of people. With mtDNA there are about 30 haplogroups. The basic answer to how this can help in genealogy is that you might find a close match and determine where your ancestors originated. It is helpful in sorting out people with common surnames such as Smith or Miller. It can tell you if you and another person had a common ancestor. Bob’s DNA was compared to others with the surname of Blackstone and similar spellings. Unfortunately he didn’t match anyone but the pool of people is small and we may have to wait until others with this same surname contribute to the mix.
The mt-DNA is generally not as helpful in genealogy but it is helpful in determining if you mother’s ancestors where Native American or any other distinct group of people. It could be helpful in a case where nothing known about a female line.
What do we know about Bob’s test?
The report from FamilytreeDNA.com suggests that his Haplogroup it R1b. The others who were tested in the same pool were R1b but there were major differences in the DNA pattern. According to Wikipedia.com, R1b1c, “Haplogroup R1b is the most frequent Y-chromosome haplogroup in Europe. Its frequency is highest in Western Europe (and due to European emigration, in North America). In southern England the frequency of R1b is about 70% and in parts of Spain, Portugal, France, Wales and Ireland, the frequency of R1b is as high as 90%.” Bob’s DNA was further broken down to a subgroup called R1b1c. It is thought that the people of this subgroup originated in central Asia and spread to Europe before the last ice age. Of course this is speculative and not proven. With further testing R1b1c can be broken down into even more subgroups but for us this will not add or subtract from the information we now have.
Part V Where now? For now I believe we have to be content until more people submit their DNA for testing. It wouldn't hurt to encourage any contacts we have with people who have that surname to contribute.