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Genetics & Genealogy
By Thomas H. Roderick, PhD, Center for Human Genetics
More of this Feature
Pt 1: Introduction & Definitions
Pt 2: Geneticists Need Genealogists
Pt 3: Family Health History
Pt 4: Genetics as a Tool in Genealogical Research
Pt 5: Y-Chromosome DNA

Special Chat!
Dr. Thomas Roderick, a research geneticist and genealogical researcher, will be our guest in chat on May 22, 2001 to answer questions about Genetics & Genealogy. This special lecture is part of an ongoing series sponsored by the Genealogical Society of Pennsylvania.

Get Chat Details Here!

Related Resources
Genetic Genealogy Projects and Links
Can DNA Replace Lost Family Records?
When You Really Want to Know: Y-Chromosome Testing

Elsewhere on the Web
Genealogical Society of Pennsylvania
Center for Human Genetics
Genetics at About




C. mtDNA AND THE UMBILICAL OR M LINE

The study of the mitochondrial DNA (mtDNA) is analogous in nearly every way with that of the Y haplotype, except that it goes up the umbilical or M line. Other terms have been used. 'Enate' and 'matrilineal' simply mean through the mother, so they could be any ancestral line going back from one's mother, for example all the lines going back from our mother's father. 'Mutterstamm' and 'uterine line' have been used by German and French researchers respectively. 'Umbilical line' has come into usage in the U.S. I prefer 'M line' because it is less earthy. Almost every language names the mother with a word beginning with 'M,' so 'M line' is highly appropriate and simple and corresponds easily with 'Y line.'

The inheritance of mtDNA is not the same as that of the Y chromosome. Mitochondrial DNA is not found in the nucleus of the cell where the Y and other chromosomes are found. Rather, it is outside the nucleus in the cytoplasm, but still within the cell. These tiny mitochondria are numerous in the cell, and they divide independently of the cell's division, but they always are retained in the cell. It is believed that these mitochondria (which are present in all animals and plants) derive from an ancient invasion of a nuclear cell by a bacterium-like organism that was not rejected, but rather gave the cell new ways to utilize oxygen in making energy. Now today, we could not survive without our mitochondria, and they could not survive without the genes inside the nucleus.

In the same way that we have a Y line back to a real Y Adam, we have an M line back to a real "mitochondrial Eve" who lived about the same time as Y Adam. But no one believes they were really mates. Although we humans on earth derive our Y chromosomes from Y Adam, and our mtDNA from mitochondrial Eve, we derive most of our nuclear DNA from all the other breeding females and males at this time in pre-history.

The M line is the hardest to trace genealogically because the surname changes each generation. For most genealogists it is among the shortest known lines. So here the DNA analysis could be even more useful in providing hypotheses for relationships and further genealogical analysis. Also it may lead to genealogies being organized around the M line descents of female immigrants, again a difficult task since under current surname practices the surname in M lines change in each generation. But I fully suspect with a couple years to see genealogies entitled "The M Line Descents from Abigail _______"

The mtDNA differences among us, as well as the Y haplotype differences can often be tied to a specific ethnic or racial group. For example there are about four unique mtDNA haplotypes that define most of the early Amerindian population (the work of Douglas C. Wallace of Emery Univ.). If you had your mtDNA analysis done, it might prove your descent from an American M line ancestress, or some other mtDNA-recognized ethnic group.

Studies being done worldwide by a growing number of DNA specialists is providing new information and insights on a monthly basis. Most of these scientific articles appear in The American Journal of Human Genetics, and others have appeared in Nature, Nature Genetics, the Proceedings of the National Academy of Science, Science and other journals dealing with human genetics. This is a 'hot' topic of scientific research from which the genealogist will benefit.

Where should we go for Y haplotype and mtDNA analyses? These can be easily found by searching the Internet. In comparing the different services these companies offer, one should take into account how many DNA sites they analyze; in general the more to discriminate between haplotypes, the better. One company does more in informing others of similar haplotype analyses from other families and DNA analyses from other families of the same surname. The cost for one analysis at the present time is around $200. With the passage of time with more efficient technology and more private companies entering this genealogical field, we can expect the number of sites to be analyzed to go up and the cost to come down.

IN CONCLUSION

By adding DNA analysis to our armamentarium of genealogical tools, we are not supplanting any of the time honored sources of primary evidence such as deeds, wills, church and cemetery records, etc. We are adding a new approach that can verify or deny established genealogical lines, provide through similar DNA findings hypotheses for where and when lines may be related and thus new areas in location and time to use the standard genealogical tools, provide understandings of relationships prior to the historical record and to provide insights into our Y line and M line ethnic heritage.


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