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DNA has been popularized in recent years due to its large use in criminal investigations and paternity cases, whereby it is used to prove a relationship to an individual. New DNA home kits have also been created over recent years and have become a popular tool for determining ancestry. As DNA is passed down from one generation to the next, there are certain parts that remain unchanged, whilst other parts do change greatly. It is this that creates an unbreakable link between generation and it can be of great use when it comes to reconstructing our family histories.
Even though DNA cannot provide you with your complete family tree, or inform you as to whom your ancestors are, it can:
- Establish whether two people are related
- Establish whether two people descend from the same ancestor
- Discover if you are related to others with the same surname
- Prove or disprove your family tree research
- Provide clues as to your ethnic origin
DNA tests have been in existence for years. However, it is only recently that the cost of testing has reduced to make it possible for the average individuals to trace their roots. Home DNA kits can now be purchased easily by mail or over the Internet. The average cost of home DNA kits are $100 to $400 per test. The kits generally consist of a cheek swab or mouthwash which is an easy way of collecting a sample of cells from the inside of your mouth.
There are two basic types of DNA tests available for genetic genealogy. These are:
- mtDNA Tests
This is contained in the cytoplasm of the cell, rather than the mucleus. It is this type that is passed by a mother to both male and female offspring without any mixing. Therefore your mtDNA will be the same as your mothers, which will of course be the same as her mothers. If the mtDNA of two people is the exact match, then there is a very good chance that they share a common maternal ancestor. However, it is difficult to determine if this is a recent ancestor or one who lived hundreds of years ago. It is important that you remember at all times that a male’s mtDNA only comes from his mother, and it cannot be passed in to his offspring.
- Y Line Tests
The Y chromosome in the nuclear DNA testing is being used in order to establish family ties. This DNA test is only available for males. This is because the Y chromosome is only passed down the male line from father to son. A distinctive pattern, known as haplotype is created by tiny chemical markers on the Y chromosome that distinguish the lineage of one male to another.
Markers on both mtDNA and Y chromosome tests can also be utilized in order to establish an individual’s haplogroup, which is a grouping of individuals with the same genetic characteristics. Interesting information can be sought from this test as to deep ancestral lineage of a person’s paternal and/or maternal lines.
DNA testing is only applicable to lines that go back through two of our eight great-grandparents – our father’s paternal grandfather and our mother’s maternal grandmother because of the fact that Y chromosome DNA is found only in the all-male patrilineal line and mtDNA only provides matches to the all-female matrilineal line. If you wish to use DNA in order to establish ancestry through any of your other six great-grandparents, then you will need to convince an aunt, uncle, or cousin who descends directly from that ancestor through an all-male or all-female line to provide a DNA sample.
Genealogists can use DNA tests to:
- Link specific individuals – e.g. to discover whether a person that you may think s a cousin descends from a common ancestor.
- Prove or disprove the ancestry of people whom share the same last name.
- Map the genetic origins of large population groups – e.g. to establish whether you have European or African American ancestry.
Before using DNA testing, it is advised that you narrow down the question that you are attempting to answer before you select the people to test. For instance, if you are attempting to discover as to whether the Tennessee COOK families are related to the North Carolina COOK families, you will need to select several male COOK descendants from each line and compare the results of their DNA tests. A match would prove that the two lines descend from a common ancestor; however, it would not be able to determine which ancestor. The common ancestor could be their great-great-father, or a male from over a thousand years ago.
When a DNA sample is submitted for testing and the results conclude an exact match, then you share a common ancestor somewhere back in your family tree. The results will not be able to indicate who the specific ancestor is, but it may assist you in narrowing down your ancestor to within a few generations.