This is a Message Board Post that is gatewayed to this mailing list. Author: RoyEKillgore_1 Surnames: Classification: queries Message Board URL: http://boards.rootsweb.com/surnames.kilgore/1607.2185.3.1.1.1.2.1.1.1.1/mb.ashx Message Board Post: This is what I understand about Y DNA Chromosome testing. The Y chromosome characterics called markers or alleles are passed on from generation to generation by males only. Geneticists have accepted a group of these markers for purposes of determining ancestry. What their criteria is for their selections are unknown to me. The geneticists have settled on the number of markers to test for at 37 since that is usually representative enough for genealogical identification. Each allele is a DNA sequence that repeats itself a number of times in a DNA strand before interruption. The number of times an allele (Marker) sequence repeats itself in the strand is the identifying number for that person. Marker 437 for me is 14 because the sequence is repeated 14 times before interruption. Everyone else I have seen is 15. Therefore the geneticists say I am at a genetic distance of 1 from everyone else. These alleles do mutate and the entire group together indicates the degree or probabilit! y of a common ancestor. Some mutate fast some slow...some decades...some centuries. If there is a group of people who share the same surname or variant thereof, the probability can be greater for a gentic matchup depending upon the surname. We have a unique and very limited use surname. If the name was Black, Brown, or White, or Carpenter, Smith, or Cooper, the probabilities would likely be much more limited. The determinations made are probabilities of having a common ancestor within a certain number of generations. What I have seen shows the results of probability based upon 4 generation intervals up to 24 generations. The mathematical calculations are based upon which allele or marker is different and the genetic distance up to 4 when testing 37 markers.. If it turns out that there is a genetic distance of 5,6,7, ot 8, it would require a continued look at 67 markers to be able to make a more definitive mathematical calculation at 24 generations of less. I have heard that! even at a genetic distance of 5 there is still a 90 percent probabil ity of a common ancestor at 24 generations with the 37 marker testfor Kilgores. I thought I could try to explain it briefly but see I have not. I think I am correct and if not, someone correct me please! Roy E. Killgore Important Note: The author of this message may not be subscribed to this list. If you would like to reply to them, please click on the Message Board URL link above and respond on the board.