Genealogy Guide: DNA & Jewish Genealogy

If you are considering autosomal DNA testing for genealogical purposes, it is advised to test the oldest generation available. This does not mean the oldest person, necessarily, but someone from the generation closest to your earliest ancestors. For Y-DNA and mitochondrial DNA testing, the age or generation is not a significant factor. For the most comprehensive results, consider also testing collateral relatives like first and second cousins. Especially if you want to test for Y-DNA and you don’t have a Y chromosome, you can recruit a male relative who carries the surname of the line you’re interested in studying.

If you have received a bone marrow or stem cell transplant, you may be ineligible for testing. Consider having a sibling or other close relative tested instead.

While DNA testing can be extremely useful to genealogists, there are some important issues to keep in mind before you choose to take a test.

Although testing companies make every effort to protect users' data, there is always the possibility that your data could be vulnerable. It’s a good idea to set up multi-factor authentication where available to make it more difficult for unauthorized individuals to access your account. You may also choose to take your test under a pseudonym or initials.

Many people are also concerned about the possibility of their DNA results being used by law enforcement after the infamous "Golden State Killer" was found using genetic genealogy in 2018. 

The testing companies Ancestry.com, 23andMe, and MyHeritage have policies that preclude law enforcement from accessing DNA matches for samples not tested at their companies. People who test with the company FamilyTreeDNA are included in law enforcement matching by default, but can opt out. This law enforcement matching is limited to cases involving identification of remains or suspects in a violent crime. Gedmatch allows law enforcement to use its matching database of all users who have opted in to those searches.

All DNA companies are required to comply with court orders, subpoenas, or search warrants. Be sure to read the terms and conditions of any DNA test before sending a company your genetic material.

You should also think about what you're willing to learn when taking a DNA test and what you will do with the information you discover. It’s not likely, but are you prepared to discover adoption, donor conception, or other unexpected parentage in your family line and expose possible secrets that affect others in your family? For guidance on handling sensitive genealogical information, consult the National Genealogical Society's Standards for Sharing Information with Others.

Finally, remember that DNA testing cannot build a family tree for you. The only way to take full advantage of DNA testing is to combine it with traditional document-based genealogy, both for your family and your matches’. While DNA can fill in frustrating gaps in your genealogical paper trail, the reverse is also true. You may not understand where different ethnic proportions come from or how some of your matches are related to you unless you also work to build a document-based family tree to compare against your matches’ trees. To learn more about how to build your family tree using genealogical documents, see our other genealogy research guides.