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What is DNA from a Genealogical Perspective, Part II

A clarification of terms can help family historians make more informed decisions about using DNA as a genealogical tool.


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Resource: GenWeekly
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Labels: DNA Study 
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DNA stands for Deoxyribonucleic acid. It is pronounced [ dee oksee ribo noo kl ik assid]. It is made up of four chemical bases: 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 four bases are combined into pairs: Adenine and Thymine (AT or TA) and Cytosine with Guanine (CG or GC). Each pair makes up the rungs of the DNA ladder and are know as the base pairs.

Functionally, DNA is like a blueprint inside every cell, except blood cells, of how to build a body. 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 results as the DNA sequence. Much in the same way as an alphabet, except there are only four letters used, (ATCGTAGC, etc.) these pairs spell out the genetic sequence.

Each cell in the 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 as focused on genetics as we are with heredity and the duplication of male DNA into the next generation. It is important to understand that male DNA, known as Y-Chromosome DNA, is most commonly used in genealogy. Female DNA, known as mtDNA, is not transferable from the male offspring. 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 along the line was not a biological father, which can occur, for example, in the case of adoption

The base pairs mentioned above 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. 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. Other sources include the web sites of various DNA testing labs and programs. You can surf the web with a search engine for informational 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 DNA mutations. Mutations are periodic alterations in the DNA, and this understanding has helped in the tracking of entire societies and cultures as they migrated across the planet.

As interesting as these TV programs are, they tend to explain broader uses of DNA rather than what the family historian needs to solve his or her own family mysteries. In my third and final article on DNA, I will explain how the researcher can go about taking a DNA sample and sending it off to be tested. I will also cover how to get the most out of DNA testing for genealogical purposes.

Source Information: GenWeekly, New Providence, NJ, USA: Genealogy Today LLC, 2010.

The views and opinions expressed in this article are those of the author and do not necessarily reflect the views of Genealogy Today LLC.

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