02/20/2025
Autosomal DNA
All humans have 23 pairs of chromosomes, each pair is made up of one chromosome from each parent. Twenty-two pairs are called autosomes and the other pair is the s*x chromosome (X and Y). Autosomal DNA is typically what is used to determine whether or not one person is related to another and how closely. Since the chromosomes come from both parents, it is possible to find relatives on both sides of the family. It can also be used to help determine genetic health traits and possible health issues but this should only be used in conjunction with medical professionals. Decisions about your health should not be made based on DNA testing alone.
Autosomal DNA tests can reliably determine relatives going back about 5 or 6 generations. Going back farther than that is possible but the relationship between two individuals (how closely they are related) becomes much harder to determine. Even for close relatives it may not be clear exactly how someone is related to you. For example: Half siblings would share approximately 25% of each other's DNA. A Grandparent / Grandchild relationship would also share approximately 25% of each other's DNA. This test will show how closely you are related but not the exact relationship.
When you take a DNA test, you will need to interpret the results to determine how each match is related to you. Understanding relationship percentages, knowing as much as possible about the family tree and understanding how to locate and interpret genealogical data are key for using DNA testing to build a genealogy and a family history.