Guild Greathouse Forum - Greathouse Family Genealogy, History, Surname Research

Guild Projects (posting requires registration) => Greathouse Surname DNA Project => : Sandy October 24, 2006, 03:46:04 PM

: Y-DNA testing for genealogists Ė why and how it works!
: Sandy October 24, 2006, 03:46:04 PM
Y-DNA testing for genealogists Ė why and how it works!

The Y chromosome in DNA follows the surname in most cultures.  The males in the line carry both the y-chromosome and the family surname.  The DNA is passed nearly identically from father to son.  There are long stretches of DNA with no known function.  These patterns of DNA are called junk markers and they can not be used to identify an individual or individual traits or medical conditions, but they can be used to track ancestral history.  These markers are passed identically from father to son, except in the rare case of a mutation.  Mutations typically occur once in every 500 generations on a single marker and a mutation on a single marker usually only shows a one point difference from father to son.  Since there are only about 12 generations of Greathouse descendants from our original immigrant ancestor, Herman Groethausen, we can expect significant matching between test participants that carry the Greathouse surname.  On a 43 marker test, we typically see an exact match or somewhere between one and three points difference for all participants.  If there is more than a three point difference, the descendancy from Herman Groethausen is unlikely.  See our test results at:

The results for the group of markers that are tested for an individual constitute the haplotype of that individual.  When you have enough participants, perhaps 10, you can infer the haplotype of the common ancestor, in this case Herman Groethausen.  When you also have the lineage of the descendants, and you have enough participants, you can actually determine which ancestor had the mutation, and what the mutation was, and infer that ancestorís haplotype.  Then, if an individual is tested, and they share the haplotype that has been inferred for the common ancestor, within about 3 markers, they can state that they are a descendant of that ancestor, even if they donít have the source documents to prove it.  We have begun to map out these mutations in our Summary results at Greathouse Points, see:

If you are female or your Greathouse ancestor is female, Y-DNA testing will not work because females donít have Y-chromosomes.  But, there is also Mitochondrial DNA testing or mtDNA testing that follows the X-chromosomes.  Itís a little harder to do because X-chromosomes donít follow the surname line, and they can be inherited from either your father or your mother.  However mtDNA testing is being done, but we are not doing it at this time in the Greathouse Point project.  So, if you are female or your Greathouse ancestor is female, it works best to find a male relative that carries the Greathouse surname.  If that male relative is tested you can use his test results to infer your ancestry.

For more in-depth information on using DNA testing to trace your ancestry, you can find additional information in the following tutorial: or the masterís class:

Please donít hesitate to contact me with your questions: