One way of learning something is to try and tell someone else about it. That is what I am doing with a few notes on DNA testing. I wasn't very strong on biology in school so I have some catching up to do. The use of DNA testing is growing for a variety of reasons. Anyone with a modest budget and some different samples of DNA can have a comparison made.
The most popular use so far has been the paternity test, to see if an alleged father is the actual father. Most states admit this as strong evidence. It can absolve a man of being the father, or it can force him into child support payments. This is the easiest test to perform. All that is needed are a few cells from the inside of the cheek, or hair follicles, or a few drops of blood (from both the alleged father and the child).
Whatever the ultimate purpose, some DNA is selected, or isolated, and broken into small fragments with enzymes. This is placed on, or in, a gel under the action of an electric field, which exerts a force to move the fragments (because they are charged). The fragments will not all move at the same speed because they have different masses. The different masses come about because there are inert spacer molecules between the active molecules. The number of inert molecules can vary without affecting the genetic action. Typically, the number of inert molecules is inherited from either the mother or father. So most of your fragments should move in the gel at the same speed as either your mother's or your father's; however, over the course of time, variations in the number of spacer molecules does develop.
As an example of DNA testing, three mummies of children were found at 22,000 feet in an ancient (say 1500 AD) Inca ruin. All three were sacrificial victims. Were they siblings? If they were from the same family, in particular the same mother, they would have the same mtDNA (mitochrondrial DNA). The comparison showed they were not siblings and were not even closely related on the maternal side.
A man, woman, and three girls were found in a burial plot in Russia. Were they the Romanov family who had been the last monarchs of Russia? The DNA testing of the man showed that he was the Tsar. From his bones, it was possible to compare his DNA with Louise of Hesse Cassel (the grandmother of Nicholas II, the Tsar), with DNA from a great-great-great granddaughter and great-great grandson of Louise. (The son of Nicholas II was not found.)
If one enters into a DNA test, one must be prepared for the unexpected. We can track family relationships and even do comparisons to people long dead.
(24 Aug 02)
We gratefully acknowledge the work of John Blankenbaker who published over 2,500 Germanna History Notes via the Germanna-L@rootsweb.com email list from 1997 to 2008. We are equally thankful to George Durman (Sgt. George) for hosting the list and republishing the notes via rootsweb.com.