DNA FOR NON SCIENTISTS BY PETER F JEFFRIES MD ABFP
Humans have 23 pairs of chromosomes in the nucleus. One of each pair is from the father; one from the mother. Each Chromosome is made up of many sites to convey information to new cells each time they divide. These sites are made up of four bases, Adenine, Thymine, Cytosine, or Guanine, (A,T,C, or G for short). The combination of these sites is called DNA or Deoxyribonucleic acid. The arrangement of these four bases produces the genetic "code." A Gene is the fundamental unit of heredity; a specific section of DNA within a chromosome.
The cell nucleus contains paired chromosomes; while the mitochondria in the cell outside the nucleus contain single chromosomes. Women have 2 X chromosomes while men have one X and one Y chromosome. The Y is passed from father to son, just as the last name is passed. Daughters also receive an X from the father. The mother passes an X to all her children. Mitochondrial X is maternal in origin. Genealogists use Y chromosome of the nucleus to study the male line and the X chromosome in the mitochondria to study the female line.
DNA analysis is a complement to standard genealogical studies and can help identify the Most Recent Common Ancestor between two people. If all sites are the same, the 2 people share common genes and thus a common ancestor sometime in the past. DNA analyses can be used for forensic means, medical needs, paternity testing and genealogy.
For genealogy we compare the DNA from different people who appear to have similar DNA. If one of the people has a proven genealogy, and they have the same DNA, it suggests a common ancestor.
We are cooperating with the FTDNA testing site to study the DNA of Sheldon descendants in order to attempt to discover the common ancestors. “The goal of the project is to see if DNA can discover a link between the early Sheldon ancestors or Progenitors.” Particularly useful is the testing of men named Sheldon. http://www.familytreedna.com
At the Strategy Planning Session, there was a request to amplify the information about the Sheldon DNA Project. In fact, there is a long list of DNA companies in the business of helping customers find their ancestry. None are called "the best." However, the International Society of Genetic Genealogy, or ISOGG, does maintain a long list of companies in the business and even lists the specialties of each company. There are 42 on the list. Thirteen address genealogy. More information is at http://www.isogg.org/wiki/List_of_DNA_testing_companies. At the Sheldon Family Association web site is a discussion of DNA by Dr John Plummer: "The Isaac Question and DNA Analysis". More discussion of DNA and Y testing is available at http://www.blairdna.com//dna101.html.
Some companies are focused on health information or inherited diseases. Other companies focus on crime solving or adoption or paternity or athletics. At recent Genealogy conferences, forums on DNA testing state that FTDNA is one of the many involved in Genealogy testing. It has one of the largest databases of European participants. Since Sheldon ancestors are likely European rather than African or Asian, it would seem to be a good choice. When a potential participant wishes to transfer from 23 & me or Ancestry, it is possible although the tests are not exactly the same and involves additional testing at FTDNA.
Issues to be considered are the size of the database, the variety of tests offered, the storage of the sample, the opportunity for upgrade, and cost. Currently, we recommend the 37 test at FTDNA. It is similar in cost to Ancestry’s 33 test. Samples will be stored for 25 years and upgrades are available. Tests from other labs are accepted
Updated 2015 The project currently has 67 members , 37 of whom are men named Sheldon. The Sheldon men are in 4 sub groups representing 2 haplogroups. Using the limited “paper” genealogical information available, there appears to be overlap between men descended from John 13 and Isaac as well as between men descended from Godfrey and John 8. Further documentation of the “paper” genealogy from these members is needed before public announcement of the results.
At the current time there are 42 members of the project, 29 of whom are men named Sheldon. The Sheldon men are in 4 sub groups. Using the limited “paper” genealogical information available, there appears to be overlap between men descended from John 13 and Isaac as well as between men descended from Godfrey and John 8. Further documentation of the “paper” genealogy from these members is needed before public announcement of the results.
To consider possible explanations of this overlap, a subcommittee of 3 members of both the project and the Sheldon Association is considering what interpretations may explain the results. If you have some science background and an interest in the project, please volunteer to help.