Thu 18 May 2006
Loading ...I haven’t posted as much this month as I would have liked, but I’ve been working on a little side project.
I’ve always been interested in genealogy, and as a scientist I’m eagerly watching the many advances in the field of Genetic Genealogy. What is Genetic Genealogy you say? Wikipedia defines it as “the application of genetics to traditional genealogy. Genetic genealogy involves the use of genealogical DNA testing to determine the level of genetic relationship between individuals.” There are four types of DNA tests for genealogical purposes:
1. Autosomal DNA Testing: This test looks at markers in the non-sex chromosomes. All humans have 46 chromosomes in each and every cell. 2 of those are sex chromsomes, and 44 are non-sex chromosomes. Researchers have identified markers in the autosomes that are indigenous to certain populations. For instance, all Europeans might have a certain marker at a certain location. If you have this marker in your genome (your genetic makeup), then you probably have some European ancestry. Autosomal tests are by nature rather vague and are only a very rough estimate of your overall ancestry. It can be very error-prone, since DNA undergoes random shuffling between generations, meaning that the genes you inherit from you parents is totally random.
2. Y chromosome DNA Testing: The Y chromosome is what gives males maleness. Men have one Y chromosome and one X chromosome. Because there is only 1 Y, there is no random shuffling between generations (or at least, very little). Thus, a son inherits his father’s Y chromosome with very little variation. The Y chromosome can be traced back through the family tree following the son’s surname. For instance, my Y chromosome comes from the original immigrant of my surname from Germany to America about 1770. My chromosome will have only a very few variations from the original immigrants Y chromosome (on average, there is less than 1 mutation per generation! And that’s after replicating 51 million base pairs!!!) The results of the Y test will tell me about the origin of the chromosome. All Y chromosomes fit into a limited number of family groups, called haplogroups, because there were a limited number of male ancestors who have direct male descendants living today. Thus, based on my results, I can get a rough idea of where my Y chromosome came from. Another useful purpose is in identifying relationships. If there is someone in Germany who has my last name and is wondering if he’s related to me, he can get the same test and the results will definitively prove our relationship one way or the other.
3. X chromosome DNA Testing: This test is in the very early stages. I won’t go into too much detail except to say that many people are still doubtful that this test will be feasible. Since women have two X chromosomes, there is a great deal of shuffling between each generation. A daughter’s X chromosome, the one she inherits from her mother, will be very different from the one her mother has. We’ll have to see how this field develops.
4. Mitochondrial DNA Testing: This is the test that I just received results from. Inside each of our cells are hundreds of a tiny organelle called the mitochondria. It produces energy from the cell and has its own tiny circle of DNA. Mitochondria, and thus the mtDNA, as it is called, are only passed down from mother to child. I received my mtDNA from my mother, and it will stop with me (although it will continue with my sister). My son inherited all of his mtDNA from my wife. So if you look at a family tree, the lineage of the mtDNA is the mirror image of the lineage of the surname. Once again, the results of the mtDNA test will reveal the origin of my mitochondria based upon which haplogroup they fit into.
So my mitochondrial DNA comes from the Cayman Islands in the 1840’s. That’s as far back as I can trace it. Interestingly, my mtDNA fits into Haplogroup A. The founders of Haplogroup A originated in East Asia and traveled across the Bering land bridge to settle the Americas roughly 25,000 years ago. Thus, my variation of Haplogroup A is characteristically Native American. This means that through my ancestor in the Cayman Islands I have inherited mitochondria from indigenous people of the Americas. To learn more about Haplogroup A, check out the website I set up to share information (www.HaplogroupA.com).
In other news, we had a fun and relaxing Mother’s Day. The E-man made a gift for Mommy at daycare using some construction paper to make a flower and then using finger paint on his hands to shape the flowers. It probably took him about 10 minutes to do the whole thing. I, meanwhile, had to go to the grocery store, the florist, and the local Hallmark store. I spent Sunday morning arranging flowers and cooking a mean breakfast. But without a doubt, the E-man’s gift beat me out hands down. He even signed a Mother’s Day card with some scribbles, the little kiss up.
