DNA stands for Deoxyribonucleic acid. It is pronounced [ dee oksee ribo noo kl ik assid]. It is made up of four chemical bases. They are Adenine (A) pronounced [a’dd nee’n] , Cytosine ( C ) pronounced [sit seen], Thymine (T) pronounced [thi meen] and Guanine (G) pronounced [gwa’ a neen]. These bases are combined into pairs. Adenine and Thymine (AT or TA) and Cytosine with Guanine (CG or GC). Each pair make up the rungs of the DNA ladder and are know as the base pairs.
Functionally, DNA is really like a blueprint of how to build a body inside every cell with the exception of blood cells. You have some 100 trillion cells in your body.
When DNA is tested, scientists put together a long line of the above base pairs which will result as the DNA sequence. Much in the same way as an alphabet, except there are only four letters used, (ATCGTAGC etc.) spells out the genetic sequence.
Each cell in your body has been designed to handle a particular function or job in the body. Like the many different types of bricks in construction, different types of cells are used for growing hair, bone, organs and other parts. Genes are sections of DNA which make proteins. Each protein enables the cells to perform its own special function. They work together to build and repair the body.
In genealogy, we are not concerned with genetics as much as we are with heredity and the duplication of the male’s DNA to the next generation. It is important to understand that it is the male’s DNA which is used. Female DNA is not transferable from male offspring, and the surname of a family allows such tests to be attributed from generation to generation. If a break in the chain of male descendent DNA does occur, it indicates that someone was not the biological father.
The above base pairs create markers. Markers refer to the physical location on the chromosome. Laboratories charge an increasing amount for tests in correlation to the number of markers tested for. The most common tests are 12, 25 or 37 markers. The more markers the greater the ability to narrow down exact matches.
There have been some very interesting programs on PBS concerning DNA and evolution. It is one source of information. You can surf the web with a search engine for other sources. I highly recommend you understand the terms, as any misunderstanding of the specialized words can cause confusion of the topic. Scientists have made great strides in the tracking of mutations. Mutations are periodic alterations in the DNA and has helped in the tracking of entire societies and cultures as they migrated across the planet.
As interesting as these programs are, they explain broader uses of DNA than what the family historian needs to solve his own local mysteries.
In my third and final article on DNA I will explain how the researcher can extract a sample from a family member, including oneself, and send it off to be tested. I will also cover how to get the most out of DNA testing for genealogical purposes.