The 100,000 Genomes Project is an NHS initiative, run by Genomics England, and is the largest national genome sequencing project in the world. On entering, patients have their entire genome, of more than 3bn base pairs, sequenced. This is different from commercially available genetic testing kits, such as those from 23andMe, which only look at very small stretches of DNA in a process called genotyping. The hope of the NHS is that having so much genetic information, from so many different people, will allow “groundbreaking discoveries about how diseases work, who could be susceptible to them, how we can treat them, and what treatments might work”.

Most of the services we tested use genotyping to read your DNA. Genotyping looks for specific markers in your genetic code. For something like ancestry testing, genotyping is effective because it identifies known variants in your DNA. Scientifically speaking, genotyping’s weakness is that it can only recognize previously identified markers. This is one reason DNA tests’ accuracy relies so heavily on the DNA database size; there must be enough information available and identified genetic variants in the database to recognize new customers’ markers.

Product Price Overall Rating Cost Ancestry Results Ease of Use Online Database Features Upgrade Option Available Geographic Regions Database Size Tester Confidence in Results Tester Satisfaction Score Overall Experience Score Sample Type Sample Collection and Registration Score Result Access and Interpretation Score Turnaround Time (Days) App Genetic Relative Connections Online Family Trees Upload RAW Data Download RAW Data
AncestryDNA has been responsible for taking DNA testing mainstream, and they now have the world’s largest autosomal DNA database. The test benefits from a number of innovative and sophisticated features such as shaky leaf DNA hints integrated with family trees, DNA Circles, Genetic Communities and New Ancestor Discoveries. A subscription is required to access some of these features and to view the full trees of your matches. The lack of a chromosome browser and matching segment data is a big disadvantage for advanced users who are interested in chromosome mapping. Many of the people now taking the AncestryDNA test are lured in by the biogeographical ancestry reports, but are not interested in communicating about genealogy. However, the test is encouraging an interest in genealogy in a subset of this market.
Most companies will use algorithms to compare the genetic variants uniquely associated to a reference population with those identified in the person being tested. This can help them exclude unlikely population groups from your ethnic mix, and ensure that the ethnic groups you’re shown to be composed of are more accurately reported. Although most companies will share the reference populations they use with their customers, they rarely provide information on the algorithms they’ve developed.
Self-collection DNA test kits are a convenient and more affordable option. However, the support and advice you receive when making an appointment to have your DNA sample taken is invaluable and we will always recommend this option to you. To locate your nearest DNA testing clinic, pharmacy or mobile sample collection service please use the location search tool.
“My concern is that more and more of these tests are being put out, and people are being persuaded to have these tests done, and they get results back that are very often of very low value and dubious helpfulness,” she says. “And often people are told to go to see their GP and that then places a direct stress on the NHS, at no cost to the company. The companies make their profits and walk away, letting the NHS sort out all the fallout, the push-back, from the test results, in a way I find absurd. Why should the NHS have to prop up the problems that these companies create?”
In order to truly understand what a DNA estimate is, we have to get a little bit scientific.  The DNA testing companies use something called “sample populations” in order to give you your ethnicity estimate.  Their laboratories compare your DNA with that of thousands of people from all over the world.  In order to become a part of the same population, the participants would have needed to prove that they and their ancestors have lived in the same geographic area for several generations.  Their DNA is then grouped by geographic area.
In addition to its ancestry test, 23andMe also offers a cool health upgrade. The upgrade costs $125 if you add it after getting your ancestry results, so we recommend splurging and buying the $199 Health + Ancestry kit from the start and it often goes on sale. It was approved as the first direct-to-consumer genetic screening service by the FDA in 2015 for certain conditions including Parkinson’s disease and late-onset Alzheimer’s disease. Many of the service’s 87 health reports are much more lighthearted, however, including information about your probability of disliking cilantro, getting bit by mosquitos or having a longer index finger than ring finger.

Alternatively, if you believe your "Italy/Greece" result indicated your known Italian heritage, it is possible that your son simply did not inherit the associated DNA from you. We all inherit roughly half our DNA from each parent, but the DNA we inherit is selected at random, and so even full siblings can have different ancestry results, depending on which genetic variants they inherited.

So, back to the example of the two men (lets call them John and James) we think might be brothers: We find two g-g-grandsons (or any male descendant in a direct father-son line) of each, preferably the most distant cousins we can find, and get a Y-DNA test done for all four men. Usually a 37 marker Y-DNA test is a good place to start. This looks at 37 sections of each persons DNA that the genetic scientists think are most useful for our purposes (the bits that are least likely to randomly change over generations). The results come back looking like a fairly meaningless string of numbers which are fairly useless on their own, but allow us to compare each persons result with others in the database of the testing company.

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. 
In testing, we found that many tests have much more specific and detailed results for European ancestry than anywhere else. This is due more to the diversity of the database than size. For example, AncestryDNA has the largest database with over 10 million samples yet results for Asian ancestry are markedly less specific than results from several companies with much smaller databases, including 23andMe and Living DNA.
Last month I did the Heritage DNA , because of one of my cousins did the test ,but hers was done by Ancestry ,I was very surprise by the result , we have nothing in commune , i was very concert concern with my result , just because it shows nothing from my family side, supposedly I’m 79.7 % Central American , 13.9% Iberian and 6.4 Scandinavian My whole family is from South America ,so why 79.9 Central American ,any way I was so intrigue that I did the Ancestry Test now , I’m waiting for the result and I’m dying to see the results
If you're creeped out by how much information Facebook, Google and Amazon have on you based on your online browsing habits, just remember that these DNA testing services are getting what is effectively your medical history. Make sure of their policies before turning over that valuable data. Also, even if you don't share your DNA with a service, your familial DNA data may be available if a relative shared their genetic material. The privacy issues can get very complex.
Y-DNA Tests: Y-DNA testing examines the Y chromosome passed only from father to son and can therefore be used to gain a better understanding of your paternal line. This can be a very interesting study for those focused on surname research, especially since the Y chromosome can give information about deep and recent roots. Because only men carry this chromosome women will need to test their father, brother or other male relation to use this test for genealogy purposes. Again, FTDNA is the leader in this type of testing and has a wealth of information, groups and forums to help.