Results of DNA Tests for Lynn Edwin Garn
Discussion of DNA and how the DNA was analyzed
Our DNA is found in 23 pairs of chromosomes that are present in the nucleus of every cell in our bodies. For the most part the pairs of chromosomes are matching pairs. The exception is the sex chromosome pair, where one chromosome of the pair in men is a Y-chromosome received from the father and the other in the pair is an X-chromosome received from the mother. In women both chromosomes in the sex chromosome pair are X-chromosomes, one received from the father and one from the mother. Our physical characteristics, such as height, hair color, eye color, etc., and some of our traits and abilities, such as intelligence and sense of humor, are determined by the genes that make up the 23 chromosomes.
Although each parent contributes one chromosome to each chromosome pair, our chromosomes are not an exact replica of those received from our parents. During the formation of our first cell, when an egg is first fertilized, the chromosomes break apart and recombine into new chromosomes, some parts of the new chromosome coming from the father's chromosome and some coming from the mother's chromosome, making each new chromosome a half-and-half, randomly shuffled mix of the chromosome material from each parent. The exception to this is in the sex chromosomes where portions of the chromosomes are preserved exactly as passed to us by our parents.
There is one more significant exception to the information presented above. This exception deals with the material that is not part of the nucleus where the chromosomes are found. It is outside the nucleus but still inside the cell. This portion of the cell has a different type of DNA, which is called mitochondrial-DNA or mt-DNA. The mt-DNA is passed solely from the mother to her child. No mt-DNA comes from the father. The current understanding of mt-DNA is that it is responsible for generating most of the energy used by the cell but that it does not participate in the governing of our physical characteristics and traits, which are governed by the 23 chromosome pairs in the cell nucleus.
Since most of our chromosomes are a half-and-half shuffling of the chromosomes received from our parents, it is impossible to establish which parent that a particular strand of DNA in a chromosome came from. Therefore, if that strand is unique to only one ethnic group, it is impossible to tell which parent had an ancestor belonging to that ethnic group based solely on the DNA data. The exceptions to this are the Y-DNA and the mt-DNA. Since portions of the Y-DNA contain DNA that is an exact replica of that received from the father, Y-DNA can reveal information about an unbroken line of male ancestors.
The counterpart to the Y-DNA is the mt-DNA, which is received only from the mother. mt-DNA can reveal information about an unbroken line of female ancestors. Also, since men have the mt-DNA they received from their mothers, tests on their mt-DNA reveal the information about their unbroken line of female ancestors. Unfortunately, since women to not have any Y-DNA, there is no way for their DNA test to reveal information about their unbroken line of male ancestors in the same way that Y-DNA does. The only way women can get specific information about their unbroken line of male ancestors is from a test taken by a brother or some other male relative who descends from the male line being researched.
One might be tempted to ask how our chromosomes could be different enough to distinguish among different ethnic groups if we all received our DNA from our parents and if, as claimed, we all have common ancestors if one goes back far enough. The reason is mutations. These occur very rarely in each new generation and then duplicate themselves in each generation thereafter. The more generations that separate two people with a common ancestor, the greater the likelihood that they will have mutations that differentiate between them.
Another factor that affects these similarities and differences of DNA is that until recently people were relatively immobile and tended to live in the same area all their lives. Over time a mutation that occurred in a particular region of the globe would tend to spread among the people of that area. And if the population was relatively immobile, as populations were thousands of years ago, the mutation would be contained to that area. As a result, people living in a particular part of the globe are more likely to have DNA similar to their neighbors than to people on the opposite side of the globe.
Although populations tended to be immobile, from time to time they did migrate from one region to another. This may have been the result of changes in weather patterns, such as those during the ice age. Or people may have moved to find better lands on which to grow crops. They may also have been driven from their lands by others who had an advantage in numbers or some other military advantage. Whenever these migrations occurred, genetic material spread from one region to another.
The analysis of the DNA involves the identification and tracing of mutations or "markers" that are passed to descendants. These markers provide a means for tracing human evolution. The earliest occurrance of each marker serves as sort of a node for divisions in the genetic tree at times thousands of years ago when an ethnic group branched off to form a new ethnic group. By identifying these nodes and the ethnic groups that descend from them, the genetic tree can be traced back to the earliest humans. In the case of modern humans, the earliest common ancestors for all of us appear to have been in Africa tens of thousands of years ago even though the genetic composition of most ethnic groups has mutated so many times that only the oldest mutations trace back to Africa.
The migration patterns derived from the genetic data are also corroborated by research in other areas, such as linguistics, where words or roots of words are similar in two different regions. These migrations explain why someone whose ancestry is European would have genetic components of ethnic groups such as those from the Mediterranian region, Eastern Asia, or Russia.
The fraction of your DNA that comes from a particular ethnic group depends on how many generations you are removed from that ethnic group. For the sake of this discussion, presume that you have an ancestor that is Chinese. If that ancestor is one of your parents and if the other parent doesn't have any Chinese ancestors, then half of your DNA should match DNA of the Chinese ethnic group. If your Chinese ancestor is one of your four grandparents and you have no other grandparent with Chinese ancestry, then a quarter of your DNA should match the Chinese ethnic group. Of course, if more than one of your grandparents had Chinese ancestry, then more than 25% of your DNA would match DNA of the Chinese ethnic group. The important thing is that the fraction of DNA of a particular ethnic group drops by one half for each generation removed that the ancestor is.
The company that tested my DNA has tested the DNA of more than half a million people. By comparing and contrasting the DNA of these people and by analyzing the genetic markers in the DNA, they are able to group people into nine different ancestral "source" populations. These nine "source" populations are:
The testing company also separated people into 43 ethnic groups. Most of these ethnic groups have DNA that is a mix of DNA from several of these nine "source" populations. The notable exceptions were Southern Africans, Oceanians, and Native Americans, ethnic groups whose DNA is relatively unmixed and constitutes a separate, unique "source" population. By comparing results of an individual DNA test, such as mine, with the 43 reference populations or ethnic groups, the testing company was able to determine which ethnic groups we descend from.