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I've done quite a bit of reading lately on genealogy-related DNA testing and have become quite interested in the process. There is a lot of scientific mumbo-jumbo out there and it can be difficult to understand at first. Hell, I was a chemistry major for a year and I even I was thrown off by some of the terms.

Basically, you have two main options for testing.

1. Y-DNA
2. mt-DNA

Y-DNA is passed father to son, like a surname. Females do not inherit Y-DNA.

mt-DNA is passed from mother to daughter. Sons also receive their mother's DNA, but do not pass it to their children.

A genealogy DNA company will then test the DNA for "markers". Markers are mutations in the DNA which help determine if you are related to someone. I understand there are over 100 "markers" present in DNA, but most companies will only test up to about 60. Another note-companies do not all test the same markers. One company may do a 40 "marker" test of marker 1-40, while another will do a test of markers 40-80.

The markers are then given numerical values. Once you have the numerical values, you can compare your results to a relative (or suspected relative).

There are a number of formulas to compute the relationship between two people who have marker matches.

Pros of DNA Testing

1. Strengthen paper trails and verify relationships.

2. Learn where a line of ancestors came from.

3. Connect with "cousins".

Cons of DNA Testing

1. Price - expect to spend at least $100 on a basic test

2. The paper research still has to be done - If you and other people have marker matches going back 12 generations, but none of you have information on the person who you all descended from, you're left with a $200 clue. (It may become useful as more people get tested however).

3. For a single male person, DNA only tests two lines - look at your family tree and think of how many lines you have - about two new lines for every marriage. Again this may change as more people get tested, and especially with the popularity of surname projects.

4. DNA tests may get confusing the farther you go back due to cousin marriage. Several of my ancestors married their cousins, then on top of that, some children married the children of their parent's brothers and sisters who had also married their cousins! I don't know if there is a term for that (double cousins?) but I would compare it to marrying a half-brother or sister, maybe even more. Without solid paper records, it is hard to distinguish between all the "cousins".

5. You may find out something you did not expect or want to find out - someone had an illegitimate child, someone was adopted, you look like an African but descend from elsewhere, ect. Better be prepared for anything.

6. Finally - my biggest concern of all - when determining if two people's ancestors are related to each other, two male descendants of each person will do a DNA test to see if their markers match. The results will come back and show whether they matched or not. Here's the catch - For example, two people are trying to prove that their ancestors were brothers. Now, if I were to create a genealogy based on faulty research and "trace" my ancestor to ancestor #1 and the other person traced his ancestry back to ancestor #2, both of us (assuming I'm a guy) doing a DNA test proves nothing. How do I know if person #1 is really my ancestor in the first place? Maybe person #2 is really my ancestor. How do I know person #2 was really his ancestor? Bringing up a previous point, there were adoptions and illegitimate children in history. We may do DNA tests and compare results, which show our "ancestors" are not related. But, because of the bad research or illegitimate children the "ancestors" really were related and we made a human error. While this problem can be rectified by testing several people, it still raises a major concern with me because of the not only the cost of testing several people, but finding those people to begin with and getting them to agree to take a test. As far as I'm concerned, half the people doing genealogy "research" are just adding other people's data to their trees without checking the data. I still can't believe it when I go on and compare people from my tree to other people's trees. I have seen hundreds of trees where a person's death date is earlier than their birth date and those exact dates are copied onto a dozen more trees. This tells me someone made a typo along the way and the rest of the world just decided to add the data without basic proofreading, a concept I thought we all learned in elementary school. Needless to say, there's a lot of bad data out there and are you willing to research other people's data before comparing results with them?

Conclusion: DNA testing can be a definite pro for many - mainly those with well-documented genealogies and several other people taking the test in order to compare results. DNA testing offers a lot of insight into where you came from, especially for African-Americans who can't trace relatives back much farther than the 17th century. However, DNA, despite being known as a highly accurate science, has its limitations, which are manifest themselves when compared with paper trails, full of human errors. I believe the most important thing to ask yourself is what you are trying to learn or get out of the test and never make a conclusion based on DNA alone.