Autosomal DNA
If you were to look inside the nucleus of one of your cells as it was getting ready to divide, you would see that it contains 46 packages of DNA. These DNA packages are called chromosomes. 44 of them are autosomes. The other two determine whether you are male or female.
Autosomes come in matched pairs. For each pair of autosomes, one came from your mother, and the other came from your father.
Each pair of autosomes is inherited in the same way. We will focus on one pair of autosomes and follow its inheritance.
Just like you received one set of autosomes from each of your parents, your parents received one set of autosomes from each of your grandparents.
Before your parents passed their autosomes down to you, each pair of their autosomes was randomly jumbled through a process called recombination.
So the autosomes that you inherited from your parents are really made up of a random mixture of your grandparents' autosomes. Going back one more generation, your grandparents' autosomes were passed to them by your great-grandparents. Their autosomes were recombined before they were passed to your grandparents, and so on. So your autosomes are random mixtures of your great-grandparents’ autosomes. As you can see, your autosomes contain a record of all branches of your ancestry, each contributing to a portion your autosomal DNA.
The genetic contribution of any one ancestor to your autosomes becomes more fragmented with each generation. So while it is likely that you and a close relative share some DNA from a common ancestor, it is less likely that you and a more distant relative share the same sections of a common ancestor’s DNA. For this reason, autosomal DNA is most informative about our more recent genetic past.