Wednesday, July 15, 2009

Searching for Your Roots -- DNA TESTING Part 1

Adopted children (and their parents too) often feel compelled to learn more about their biological family. Often, this can be a long and complicated process and may have varying results. In some cases, DNA testing is done in order to prove paternity or maternity when a person is found that may be the biological father or mother.

However, DNA tests can be used to help adoptees in their search for self-identity in other ways. In fact, DNA tests can serve 3 purposes. The first, is, of course, the most obvious, however, the others may be of equal value in discovering more about your past.
  • 1 - Link specific individuals -- For example, testing to see whether you are the child of a certain man or woman.

  • 2- Prove or disprove the ancestry of people sharing the same last name -- For example, testing to see if males carrying the GARCÍA surname are related to one another.

  • 3- Map the Genetic Origins of large population groups --- In this case, you test to see whether your deep genetic roots show whether you have European or African American ancestry. This is often called your personal map of Human Migration.

The kind of DNA test I would like to talk about today is the THIRD KIND.

This kind of test does not link you to a specific person, but rather, it links you to a geographic region. It tells you, you are 30 % European, 5% African, 60% Native American, and 5% Asian etc.

Some DNA testing agencies can give you even more specific information.

There are two methods for mapping human migration. They're not 100% accurate as they only track, at most, 2 ancestral lines.

For females, they test the mitochondrial DNA, or mtDNA. The mitochondrial DNA is the DNA that makes up the actual material that make up your cells. Rather than your own DNA, which is generally inside your cells -- that's how I understand it, at least. Your mtDNA is a direct hand-me-down from your biological mother, who received it directly from her biological mother, and on down the line of your maternal ancestors.

For males, you can sequence the mtDNA in the same way. However, you can also sequence the Y chromosome. The Y chromosome is a direct hand-me-down from the biological father, who got it from his father, who got it from his father, etc.

Once sequenced, either of these DNA models can then be analyzed for "markers" in the DNA. Markers are evolutionary traits. Maybe an ancestor was the first person to have blue eyes in the family tree. Well, they would throw a marker into the mix. Now,anyone with that particular marker would be a descendant of that 1 person. Once they have your markers, they can compare them with other known samples containing the same and different markers, and generalize where your ancestors migrated from. For example, Marker A occurred in South America 5,000 years ago. Maybe Marker B occurred in Asia 20,000 years ago. And maybe Marker C occurred in what is now Persia 65,000 years ago.



Stay tuned: The Adult Adoptee perspective on DNA testing tomorrow

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