I know this is long, but it helps explain the DNA stuff a little.The microchondrial part wouldn't help me because my Bearce ancestors are male all the way to my father. Sounds like it will be awhile before DNA testing is routinely used in genealogy. Hope this helps. Susan
DNA ANALYSIS: The Newest Genealogical Tool? > >by John ThompsonJohndnaguy@aol.com > > The good news is that your entire family history is stored > securely and unambiguously in your DNA. The bad news? It is not > so easy to decipher and it covers only the identities of your > ancestors, omitting details on their lives. So what can > genealogists expect from DNA in the near future? To understand > this, a little knowledge of genetics is required (but not much). > Any pair of unrelated people has exactly the same DNA sequence > at about 99.8% of the three billion positions in human DNA. > Related individuals have an even higher level of identity. Close > family relations can be confirmed by comparing the DNA sequence > at positions that tend to vary more often than average (the > differences can be either in the sequence of DNA present or its > length). It is relatively easy to determine identity (like in > forensics) or very close relationships (like determining > paternity) but it becomes progressively more difficult to > analyze more distant relationships. > > Each person has 23 pairs of chromosomes in nearly all the cells > in their body with one of each pair contributed by the mother > and one by the father. 22 of the pairs are virtually identical. > One of the pairs is the sex chromosome that can be either XX > (women) or XY (men). Each person gets one X from his or her > mother and either an X or a Y from his or her father. In > addition, most cells have hundreds of copies of mitochondrial > DNA that is much shorter than the chromosomal DNA and comes only > from your mother. If the DNA behaved itself and tracked nicely > from one generation to the next, molecular genealogy would be > easy. However, there are changes in the DNA in every generation > (if you think transcribing census records is tough, try getting > 3,000,000,000 base pairs of DNA right every time). Also, the > individual chromosomes in the pairs recombine with each other, > mixing up the parents' contributions in each generation. Thus, > each of your great-grandparents supplied one-eighth of your DNA > but their contributions are scattered throughout all of your > chromosomes and not so easy to track, especially since each of > your great-grandparents was 99.8% identical to the others to > begin with! > > There are a couple of special cases that are easier to deal > with. The simplest DNA to look at is the mitochondrial DNA > (from only the mother) and the Y specific DNA (from only the > father). More has been done with mitochondrial DNA because it is > easier to work with. It is much shorter and there are many more > copies of it, but it can only be used to trace maternal > lineages. If you and the person of interest share the same > mitochondrial DNA sequence, you must have the same maternal > ancestor some generations back. Not enough has been done to know > how much identity is needed to prove common ancestry because, as > mentioned earlier, DNA sequence changes slowly as you traverse > generations. A very detailed account of how this type of > information was used to identify century-old bones is presented > in THE ROMANOVS: THE FINAL CHAPTER, by Robert Massie. > > Y-specific DNA can be used to trace paternal lineages. Since the > mother does not have a Y chromosome, the father's contribution > remains "pure." One good example of using Y DNA was confirmation > of a relation between Thomas Jefferson and the offspring of > Sally Hemings (see the scientific journal NATURE, Volume 396, > p. 27). It is important to note that with both the Romanovs and > Jefferson/Hemings examples, DNA alone was not used to prove a > genealogical relationship. A lot of research went into > documenting historical data and providing a specific hypothesis > that was then put to the DNA test. It is likely that this will > remain the predominant use of the technology for the foreseeable > future.