Popularized in recent years by its use in high-profile criminal investigations and paternity cases, DNA, deoxyribonucleic acid, is most commonly used to prove a relationship to an individual. New tests created in recent years, however, have also turned DNA into a popular tool for determining ancestry. As DNA is passed down from one generation to the next, some parts remain almost unchanged, while other parts change greatly. This creates an unbreakable link between generations and it can be of great help in reconstructing our family histories.

While it can't provide you with your entire family tree or tell you who your ancestors are, DNA testing can:

• Determine if two people are related

• Determine if two people descend from the same ancestor

• Find out if you are related to others with the same surname

• Prove or disprove your family tree research

• Provide clues about your ethnic origin

There are two basic types of DNA tests available for genealogical testing:

• mtDNA Tests - Mitochondrial DNA (mtDNA) is contained in the cytoplasm of the cell, rather than the nucleus. This type of DNA is passed by a mother to both male and female offspring without any mixing, so your mtDNA is the same as your mother's mtDNA, which is the same as her mother's mtDNA. mtDNA changes very slowly so it cannot determine close relationships as well as it can determine general relatedness. If two people have an exact match in their mtDNA, then there is a very good chance they share a common maternal ancestor, but it is hard to determine if this is a recent ancestor or one who lived hundreds of years ago. It is important to keep in mind with this test that a male's mtDNA comes only from his mother and is not passed on to his offspring.

• Y Line Tests - More recently, the Y chromosome in the nuclear DNA is being used to establish family ties. The Y chromosomal DNA test (usually referred to as Y DNA or Y-Line DNA) is only available for males, since the Y chromosome is only passed down the male line from father to son. Tiny chemical markers on the Y chromosome create a distinctive pattern, known as a haplotype, that distinguishes one male lineage from another. Shared markers can indicate relatedness between two men, though not the exact degree of the relationship. Y chromosome testing is most often used by individuals with the same last name to learn if they share a common ancestor.

Example: The DNA tests supporting the probability that Thomas Jefferson fathered the last child of Sally Hemmings were based on Y-chromosome DNA samples from male descendants of Thomas Jefferson's paternal uncle, since there were no surviving male descendants from Jefferson's marriage.

Markers on both mtDNA and Y chromosome tests can also be used to determine an individual's haplogroup, a grouping of individuals with the same genetic characteristics. This test may provide you with interesting information about the deep ancestral lineage of your paternal and/or maternal lines.

What You Can and Can't Learn From DNA Testing

Since Y-chromosome DNA is found only within the all-male patrilineal line and mtDNA only provides matches to the all-female matrilineal line, DNA testing is only applicable to lines going back through two of our eight great-grandparents - our father's paternal grandfather and our mother's maternal grandmother. If you want to use DNA to determine ancestry through any of your other six great-grandparents you will need to convince an aunt, uncle, or cousin who descends through an all-male or all-female line to provide a DNA sample. Additionally, since women don't carry the Y-chromosome, their paternal male line can only be traced through the DNA of a father or brother.

DNA tests can be used by genealogists to:

• Link specific individuals - e.g. test to see whether you and a person you think may be a cousin descend from a common ancestor

• Prove or disprove the ancestry of people sharing the same last name - e.g. test to see if males carrying the CRISP surname are related to each other

• Map the genetic orgins of large population groups - e.g. test to see whether you have European or African American ancestry

What is your goal?

To best use DNA testing to learn about your ancestry you should start by narrowing down a question you are trying to answer and then select the people to test based on the question. For example, you may wish to know if the Tennessee CRISP families are related to the North Carolina CRISP families. To answer this question with DNA testing, you would then need to select several male CRISP descendants from each of the lines and compare the results of their DNA tests. A match would prove that the two lines descend from a common ancestor, though would not be able to determine which ancestor. The common ancestor could be their father, or it could be a male from over a thousand years ago. This common ancestor can be further narrowed down by testing additional people and/or additional markers.

Most Recent Common Ancestor (MRCA)

When you submit a DNA sample for testing an exact match in the results between you and another individual indicates that you share a common ancestor somewhere back in your family tree. This ancestor is referred to as your Most Recent Common Ancestor or MRCA. The results on their own will not be able to indicate who this specific ancestor is, but may be able to help you narrow it down to within a few generations.

What can I learn from my results?

An individual's DNA test provides little information on its own. It is not possible to take these numbers, plug them into a formula, and find out who your ancestors are. The marker numbers provided in your DNA test results only begin to take on genealogical significance when you compare your results with other people and population studies. If you don't have a group of potential relatives interested in pursuing DNA testing with you, your only real option is to input your DNA test results into the many DNA databases starting to spring up on the Net, in the hopes of finding a match with someone who has already been tested. Many DNA testing companies will also let you know if your DNA markers are a match with other results in their database, provided that both you and the other individual have given written permission to release these results.

In conclusion, it is vitally important to keep in mind that DNA testing for the purposes of proving ancestry is NOT a substitute for traditional family history research. Instead, it is a tool to be used in conjunction with family history research to aid in proving or disproving suspected family relationships. It is definitely an exciting new tool to add to your genealogy toolbox!

Initially, one of the goals of the project is to determine whether most Ragsdales are derived from one common ancestor or whether there were several initiating ancestors. Other goals are to determine what lines are derived from one Godfrey Ragsdale, the patriarch of a well documented Ragsdale line in the United States.

The primary company that is doing the DNA analysis in this study is Family Tree DNA. As a member of our Ragsdale surname group, the cost for a 12 marker Y-chromosomal DNA test by FTDNA is $99, for a 25 marker test is $148, and for a 37 marker test is $189. In addition, there is a $2 postage charge for US residents and $4 for mailing the test kits to foreign addresses. If you initially obtain results for 12 or 25 markers, you can (for a fee) upgrade to more markers at a later date without sending a new test sample since the company stores your original sample for several years. It is strongly recommended that participants in our DNA project choose at least the 25 marker test, however, if cost is a concern, you can certainly feel free to just have the 12 marker test run initially (or contact me and we will see about using the "general fund" to help defray the associated cost).

Each participant is given a personal page on the FTDNA web site where the participant's test results, and comparisons of the results with others in the FTDNA database, can be viewed when the results become available (typically 4 to 6 weeks after FTDNA receives the test kits back in their facility). Most communication with participants is by email but FTDNA also eventually sends each participant a written report and certificate with that person's results. From time to time a summary of the results obtained by all members of the group will be posted at this web site. Names of sample donors will not be used in the web reports; the results will be linked only to the earliest known Ragsdale ancestors of each participant. In this way the results become useful since it is by comparing the results of each participant with those of others that meaningful genealogical conclusions can be drawn.

In this study 12, 25 or 37 markers (the 25 or 37 marker test is recommended) in the DNA of the Y-chromosome of each sample are examined. The Y-chromosome is unique in human DNA in that it is only found in males and is passed down from father to son virtually unchanged. The term 'virtually' is used because there is a small probability (less than 1 %) that a mutation will occur in the markers each generation. The net result then is that the markers being examined will have essentially the same (or very similar) values for you, your father, grandfather, great grandfather, etc., back many generations (10 to 50 or more). Obviously one cannot directly analyze such DNA back more than 2 or 3 generations because earlier ancestors have passed on. However, the power of the technique is that one does not have to analyze the DNA of ancestors; one can obtain meaningful genealogical information by comparing the results from your DNA analysis with the results from others. Consider, for example, that your direct male ancestor of say 10 generations ago had 2 sons, one of whom you are descended from, and the other who is the ancestor of another group of Ragsdales. The Y-chromosomal DNA from a living direct male descendant of the second son should be identical or very similar to your Y-chromosomal DNA. The corollary of course is that, if neither you nor the other Ragsdale knew your lines back that far, finding your DNAs to be so closely matched would indicate that you have a common ancestor. That could open up new avenues for both of you to explore. Of course, if you find that your Y-chromosomal DNA does not match that of another Ragsdale one could conclude that you are not closely related (at least through the Ragsdale male line).