McCartney says that anxious people often contact her, saying they wished they hadn’t done the tests. “These companies often say that it’s worth it for the helpful advice. But I can give you really good advice right now without seeing a single test result: be active, have lots of social networks, do work you enjoy, try not to smoke or drink too much, don’t be overweight or underweight, eat lots of fresh fruit and vegetables. Nobody needs to get tests done to get that kind of basic lifestyle advice.”
If you are concerned about your data being sold, your concern may be valid. In the past, records have been sold and de-anonymized. It is possible for genetic information to be used to find the name of the individual the DNA came from. This can happen regardless of whether or not your name was in the database. This scenario has occurred in the past.
HomeDNA has the simplest DNA extraction process; just swab each cheek twice with a cotton swab, and place the swabs in the included envelope. The National Geographic Genographic Project sent a scraper that you use on each cheek for 45 seconds, and then place in a vial with stabilizing liquid. MyHeritage DNA has a similar process. 23andMe and AncestryDNA require that you spit into a tube up to the fill line (harder than it sounds), and ship it back with stabilization liquid. Most of the services said not to eat, drink, or smoke for 30 minutes to an hour prior to testing to get the best possible sample.
Similarly, mitochondrial DNA, or mtDNA, is used by direct-to-consumer DNA tests to trace your direct maternal lineage and determine maternal haplogroups. While most DNA lives in your cells' nuclei, mtDNA lives in the mitochondria. Mitochondria are the cells' powerhouses – their 37 genes are necessary for cellular energy production and respiration. Previous research suggested that mtDNA is inherited directly from your mother, but a recent study found that biparental mtDNA may be more common. This discovery may affect maternal haplogroup testing in DNA tests in the future, but for now, it’s safe to assume your results are correct.
More controversially, some of these kits profess to tell you your biological (as opposed to actual age) by measuring the length of your telomeres (in basic terms, the caps at the end of each strand of DNA that protect chromosomes, like plastic tips at the end of shoelaces). Other tests, such as 23andMe, predict higher risks of developing serious conditions, such as multiple sclerosis, Alzheimer’s and Parkinson’s, including the test for BRCA1/BRCA2 (breast and ovarian cancer) that Angelina Jolie famously underwent, going on to have a preventative double mastectomy and surgery to remove her ovaries.