Health and disease info: DNA testing can also indicate which conditions for which you may have a preponderance. It's a controversial feature, to be sure. Knowing that you have a genetic predisposition to a certain form of cancer may make you more vigilant for testing, but it may also lead to increased stress -- worrying about a potential condition that may never develop, even if you're "genetically susceptible" to it. The possibility of false positives and false negatives abound -- any such information should be discussed with your doctor before you act upon it.
As with traditional genealogical research, DNA testing can provide surprises so be prepared for the unexpected. You might uncover family secrets by matching with a cousin or a half-sibling that you didn’t know existed. Conversely a relation who is expected to share DNA with you might turn out not to be a genetic relative at all. In rare cases, people discover that their parents are not their biological parents. For a good overview of the ethical implications of DNA testing see the Genetic Genealogy Standards.
Note that DNA testing isn't the only kind of kit that collects physical evidence from you these days. Ubiome is one noteworthy example. The service evaluates your microbiome—basically the bacteria that live in and on you. In our review, we took its gut biome test, which required our intrepid reviewer to send in a poop sample (insert poop emoji here).
Every human carries two copies of the genetic code, one inherited from the mother and one from the father, some 6 billion letters in all. Apart from identical twins, no two individuals have the same genetic code.  With the exception of the egg and sperm cells, all the cells of our bodies have 23 pairs of chromosomes, 46 in all. One chromosome of the pair is inherited from the father and one from the mother. However, in males the 23rd pair consists of a so-called Y-chromosome and an X-chromosome, whereas females have two X-chromosomes.  The Y chromosome contains a gene which triggers embryonic development as a male and carries information about the male’s paternal lineage.
If you have the Health + Ancestry Service you have access to the full 23andMe experience. If you only have the Ancestry Service, you can easily upgrade to the Health + Ancestry Service for £90 which gives you access to all 125+ reports on ancestry, traits and health. You are eligible to upgrade once you have received your Ancestry reports. To upgrade, log in to your 23andMe account and navigate to the Settings page. You will receive immediate access to your new health reports.
There are a number of reasons why the vast majority of living humans are a blend of ethnicities. Firstly, from around 1850 onwards, people started to migrate around the world and mix in large numbers. Secondly, as national borders have changed over time, the only clear cut ethnic groups are those that are highly isolated. For example, as individuals have migrated in large numbers between France and Britain in the last few thousand years; those in Northern France exhibit a similar ethnic mix to those in Southern England.
GEDmatch is a service where anyone with raw DNA data can upload it, see a list of cousin matches and use a powerful selection of advanced tools to analyze their data. The service is free and powered by donations (extra tools are provided to those that donate). From parental phasing and triangulation, to a variety of admixture calculators and a robust database of people from all testing companies, GEDmatch is the best place to go to explore your genetic data in detail. The system accepts raw data from any one of the main testing companies and has a proven track record of properly managing user information.
Offering DNA test kits and a range of online subscription services, MyHeritage says that its database includes more ethnicities -- that's 42 -- than any other major testing service. The free 14-day trial will let you poke around the company's massive online database which includes 3.5 billion profiles in addition to information about over 100 million subscribers and their collective 46 million family trees. 

Living DNA supports 80 geographical ancestry regions, 21 of which are located within Britain and Ireland alone, making it a great DNA test for people wanting to delve deep into their British heritage. Of course, it also covers 60 regions outside of the British Isles, and is expanding its efforts to bring the same level of detail to other world regions.

Who knows how much of it made solid scientific sense? However, I have to confess that I rather enjoyed it on the level of an indulgent genome-oriented “pampering session”, just as I had a hoot with the ancestry/Neanderthal/earlobe data on 23andMe. Where Thriva is concerned, I also noted that it did advanced thyroid tests. Although such tests are available from the NHS, I’m hypothyroid myself and I know that sometimes it can be difficult and time-consuming getting tests repeated and it could be useful to be privately tested in this way.

As discussed earlier, in order to determine the ethnicities present in your genetic make-up, genetic ancestry companies can analyse your autosomal DNA to seek out the genetic variants uniquely associated to certain population groups. These groups are known as ‘reference populations’, and they’ve been constructed by sampling the DNA of modern populations around the world, as well as from human remains at various archaeological sites. By identifying these genetic variants in your genetic code, companies can report on the groups that have contributed to your DNA.
When you get your 23andMe results, it takes you to an easy-to-navigate dashboard with your ancestry composition report front and center. Testers reported both high levels of confidence in the accuracy and high rates of satisfaction with the contents and detail of their results. The service breaks down the world into 171 populations, based off its reference panel of 10,000 individuals with known ancestry. Some of these population groups are a tad redundant. For example, I received hits for South Korean, Korean, Broadly Japanese & Korean, and Broadly East Asian in my report, which all represent a similar area but show different levels of certainty. Scrolling down your ancestry summary, you can also view your ancestry timeline. This estimates how many generations back your most recent ancestor from each of your matched regions probably lived. You can also view your ancestry composition mapped out on chromosomes. This view is interesting, as you can change the level of confidence from speculative to conservative, which equates a match percentage of 50 to 90 percent.
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. 

In McCartney’s view, enough testing is already done in this country (sometimes too much) and there are issues of regulation and “informed consent”. “People are given very dramatic reasons to have these tests – it could help save your life, it could help improve the quality of your life – but where is the actual controlled evidence that these tests have ever done that? There’s no evidence that says doing these tests makes people become healthier.”
We each had two ancestors one generation ago, four ancestors two generations ago, and by the time we’ve gone back five generations, 32 ancestors have each contributed approximately 3% of our autosomal DNA! As an ethnicity test can’t show you how your autosomal segments have been passed from one generation to the next, trying to derive meaningful information about the ethnicities of your ancestors more than five generations ago is virtually impossible.
The Y chromosome is a special chromosome, passed on from fathers to their sons, while mothers pass on mtDNA to both their sons and daughters. But mtDNA dies with men and so it survives only in the female line. This means that a man’s lineage can be followed along both paternal and maternal lines, while in a woman only her maternal or mtDNA line can be followed.