Home

DNA Testing for Genealogy

Several friends have asked for advice on DNA testing for studying their family history; this is a summary of advice for 2017.

Be Prepared for Surprises

The first thing that I tell people is to be prepared for surprises:

  • If you have white ancestors who lived in the South during the slavery and reconstruction eras, it is highly probable that you will get a DNA match from a second, third, fourth or fifth cousin who is black. Slave owners raped female slaves, who then got pregnant and had children. Given the number of fourth cousins that you have, it is almost a certainty that you will have at least one genetic match who is black.
  • Your parents or grandparents may not be your biological parents or grandparents. It is not routine, but it is also not unusual for your dad not to be your dad.
  • You may discover siblings that your mom or grandmother had out of wedlock. Again, this is not routine, but it is also not unusual.
  • Some relatives may have committed crimes with no (or very long) statutes of limitations (or think someone else did) and may be adamantly opposed to DNA testing for no apparent reason. The genealogy DNA testing services intentionally fail to keep an evidentiary chain of custody, but this will not allay the fears of some family members.

Who Should You Test?

The short answer is the oldest living generation that you can. The long answer depends upon the specific genealogical research problems that you are trying to solve. To prove/disprove a particular relationship from the late 1700s, I am trying to find someone provably descended from a potential male direct line who has done a Y-DNA test. We would not know whether we are related until after testing has been done.

Generally, try to get tests from parents and grandparents who are living, and then look for specific people to solve specific problems.

What Tests Should You Purchase

The key for all of the testing services is to get a DNA sample, and have a single test done. Once they have a sample, they can do additional tests from that sample at a later date as your are willing to spend more money. The short answer for parents and grandparents is everything:

  • For men, get a Y-DNA, autosomal DNA and mitochondrial DNA tests done.
  • For women, get both autosomal and mitochondrial DNA tests done.

Y DNA

Only men can take this test. It can prove/disprove a match the direct paternal line for many generations, as there is no dilution from one generation to the next, and the mutation rate is generally about one every four generations.

Autosomal DNA

Both men and women can take this test. It can identify the presence of a relationship back about four or five generations, but it will not tell you what the relationship is. It is diluted 50% with each generation, and is thus limited to about five generations.

Mitochondrial DNA

Both men and women can take this test. It can prove/disprove a match for the direct maternal line for many generations.

X DNA

Both men and women can take this test. This is a specialized test that is useful only proving very specific relationships.

Which Service Should You Use

This is a long complicated subject; people with unlimited budgets test with all of the services, since the value of each service is related to the number of people who test with that service. Some of the services allow you to unload data from competing services and upload it to their service, but this is not universal and changes from year to year. The key to testing parents and grandparents is to get a sample kit activated at both the Family Tree DNA and Ancestry DNA services. It probably helps to outline the major testing services:

All of the services offer an estimate of your ethnic origins; those who have tested with multiple services laugh at this, as each service gives different, and sometimes significantly different results.

If your parents or grandparents are the first generation to immigrate to the US, you may want to look at testing with MyHeritage, as it may have a larger European population for matching.

Test Men with Family Tree DNA and Optionally Ancestry DNA and/or MyHeritage

Family Tree DNA is the only service that offers the Y-DNA test, so you should get a kit from Family Tree DNA and do at least the Y-DNA test with them. You can do an autosomal test with either Ancestry or Family Tree DNA. I would recommend getting kits from both, doing Y with Family Tree DNA, and autosomal with Ancestry, then upload your Ancestry autosomal info to Family Tree DNA. At a later date, you can optionally order an autosomal or X-DNA test from Family Tree DNA. The key for testing parents and grandparents is to get the samples to each of the services.

Test Women with Family Tree DNA and Optionally with Ancestry DNA and/or MyHeritage

It is not clear that Ancestry offers a mitochondrial test, so I recommend ordering a mitochondrial test from Family Tree DNA and an autosomal test from Ancestry, then upload your Ancestry autosomal info to Family Tree DNA. At a later date, you can optionally order an autosomal or X-DNA test from Family Tree DNA.

For Genetic Diseases, Test with 23 and Me

For most people I would not recommend testing with 23 and Me due to concerns about privacy. Both Family Tree DNA and Ancestry DNA were created primarily for genealogical research and intentionally chose genetic markers that have no known disease information; if you testing results were to become public, it would not have an effect on your insurability.

23 and Me was formed primarily to build a pool of people with specific health-related genetic information to make it easier for pharmaceutical companies to do clinical trials for drugs that are targeted for specific populations, like women who are negative for the BRCA2 breast cancer gene. For this reason, the 23 and Me privacy policy is very different from the privacy policy at Family Tree DNA and Ancestry DNA.

If you are interested in health information, 23 and Me is the only option, but make sure that you understand the privacy policy and the implications for purchase of 23 and Me by a pharmaceutical company.

DNA Seminars

The Dallas Genealogical Society has a DNA Special Interest Group that meets at the downtown library on the third Thursday evening each month.

Diane Southard and Cece Moore are among many consultants that hold frequent seminars and speak on DNA topics at local historical and genealogical societies.

Add comment


Security code
Refresh

Server Time is
Browser time is

This site uses cookies to improve the user experience. Click on "More Info" to learn more about the privacy policy and the way cookies are used.