Jewish DNA - What's Different?
"No, You Don’t Really Have 7,900 4th Cousins: Some DNA Basics for Those With Jewish Heritage"
Traditionally, we have researched our family history by interviewing our elders, visiting data repositories and Internet sites, and creating our tree in an orderly manner. Science has intervened to bring us Genetic Genealogy so that we can interpret our DNA and compare it with that of others. Every day we are deluged with advertisements touting how this or that company can best interpret our test and match us to the most relatives.
Autosomal DNA is a term used in genetic genealogy to describe DNA that is inherited from autosomal chromosomes. An autosome is any of the numbered chromosomes, as opposed to the sex chromosomes. Humans have 22 pairs of autosomes and one pair of sex chromosomes, the X (Female) chromosome and the Y (Male) chromosome. Ancestry claims over 4 million kits have been tested. MyHeritage, 23andMe, and Family Tree DNA have smaller databases. Each has advantages and disadvantages.
In genetic genealogy, a centiMorgan (cM) is a unit for measuring genetic linkage. The genetic genealogy DNA testing companies use centiMorgans to denote the size of matching autosomal DNA segments. When we get a "match", it is initially reported as a relationship such as 2nd cousin or 3rd cousin twice removed (3C2R). AncestryDNA reports I have 1,000+ 4th cousins or closer and more than 5,000 5th-8th cousins.
Each company can only give you matches to others in their database. Many people are loading their DNA results into GEDmatch, a free program that consolidates the data that are uploaded to the program from multiple testers.
The X Chromosome
The X chromosome has special inheritance properties that allow people to use these results separately from the rest of the autosomal results, although the X chromosome is a part of the 23 sets of chromosomes used for autosomal testing. The inheritance paths are different for males and females, because males only inherit an X chromosome from their mother (and a Y from their father which makes them male), but women inherit an X from both parents.
Mitochondrial DNA is passed from mothers to both their sons and daughters, but it is only passed on by females. Males carry their mothers' mitochondrial DNA (mtDNA), but they don’t pass it on. Mitochondrial DNA testing provides a haplogroup which defines deep ancestry, such as European, African, Asian or Native American. Family Tree DNA is the only commercial company to offer full sequence testing, which is sometimes necessary to determine whether a match is really genealogically relevant.
Y-Line testing looks at the Y chromosome, which is passed from father to son along with, in most cases, the surname. Only men can test for this because only men have a Y chromosome. Female genealogists must ask their fathers, brothers, uncles, and male cousins to test for the surnames in question. (At this writing, only Family Tree DNA does Y-line testing)
A Hapolgroup is a genetic population group of people who share a common ancestor on the patriline or the matriline. Haplogroups are assigned letters of the alphabet, and refinements consist of additional number and letter combinations, and refinements consist of additional number and letter combinations. A quick comparison of a test individual's mitochondrial DNA at the following three vendors shows the following; 23andMe, Jic2; Living DNA, Jic; Family Tree DNA Full Sequence, Jic2f.
Disclaimer: The Jewish Genealogical Society of Geater Kansas City, its members and affiliates do not endorse or recommend a specific vendor and make no claim or guarantee for the results of the use for any purpose of the forgoing programs