There are mixed reactions to the use of ancestry DNA databases in criminal cases. On one hand, the rise of readily-available DNA information for millions of people has led to the arrests of several suspects related to long-cold cases, including the arrest of the Golden State Killer. On the other hand, law enforcement accessing private databases of genetic information from consumers raises several questions regarding privacy and ethical issues.
This is another feature of these genetic-testing sites – they are littered with caveats and disclaimers, forever emphasising that they’re not actual “diagnostic tests” and, if you are really concerned by your results, to seek further advice from your GP or another health professional. As has been pointed out by McCartney, when anything looks serious, ultimately it’s back to the very GP and exact NHS infrastructure that these kits profess to smoothly bypass.
When asked about how database size affects ancestry results, David Nicholson, co-founder of Living DNA, told us, “The tests absolutely rely on the reference database. If you have Polish ancestry but there are no people in the database who are Polish, then what the test will do is show what the next closest group is next to Polish, like German or Eastern European ancestry.” Each ancestry DNA service has its own sample database and reference panel made of the DNA samples collected from their users and information collected from sources like the 1000 Genomes Project. The database consists of all this information collectively. A reference panel is made of certain curated samples with known family history and roots in a specific place. The services use insights gleaned from the reference panel to give you geographical ancestry results. In theory, a larger database leads to more information available to create a good reference panel, which then leads to better results for customers.  
In addition to showing geographic ancestry percentages, some direct-to-consumer DNA tests also include insights about physical traits like hair and eye color. With 23andMe, this trait information is mostly available in the upgraded Ancestry + Health kit, but some interesting tidbits can be found in the Your DNA Family report, which is available if you opt to participate in the DNA Relatives service. This report tells you interesting information, such as that your DNA relatives are 32 percent more likely to own a cat or 11 percent less likely to have lived near a farm when they were young. DNA Passport by Humancode offers information about more than 20 physical traits, from appearance to grip strength. Ancestry DNA recently added its AncestryDNA Traits upgrade for $10, and it lets customers who have already taken one of its tests unlock information about 18 genetically influenced traits, including bitter taste perception, freckles and cilantro aversion.
Gteat article! Thank you so much. I am Jewish American. Both sides of my family immigrated from Eastern Europe/Russia about 5 generations ago. I would really like to try and find out more about exactly where they came from, identify potential living and deceased distant relatives in the USA and abroad and ultimately start creating an extensive family tree. Which test would you suggest?
Whether it’s an autosomal test, a Y-DNA test or an mtDNA test, virtually all providers use the same science. Some providers offer an ‘off the peg’ solution such as Ancestral Origins™ or AncestrybyDNA™, so if you’re interested in these you should shop around for the lowest price. Most providers offer a test that interprets and presents the results in a unique way, so if one of these catches your eye, look for examples of how the results are presented on their website before you buy.