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.” 

Lets suppose, as we have in the Sinnott/Sennett one name study, we have a whole lot of families who all believe their common ancestor came from Co Wexford, but the paper trail for conventional genealogy research has dwindled away, or we suspect that John and James who emigrated to the US about the same time were brothers but there is no documentation to prove it – genealogical DNA studies can now be used to show whether its possible that two families (that are at the moment quite separate on paper) are actually related and have a common ancestor. And no, we don’t have to go digging up g-g-g-g-grandfather John to get his DNA – remember, he passed it on to his son, and his son’s son, and so on to the present day. So we find a living male descendant and they get their Y-DNA analysed. That gives us a pretty good indication of the genetic signature for the whole family tree (well, the male side, anyway). If we want to check it, we find a distant cousin of the first person who tested and get their DNA analysed. If its a very close match, then bingo – we know the Y-DNA genetic signature (and whats known as a haplogroup) for our whole family group.
The DNA test thing is a scam as the results cannot have precision. I know where my recent ancestors came from and wanted to “test a DNA test”. My ancestry is 3/4 Spanish Valencian and 1/4 Spanish Ibizean (Ibiza): I have family papers and village names for my recent ancestors: they all have typical Spanish/Catalan names and I expected this to be reflected in my results.
Lets suppose, as we have in the Sinnott/Sennett one name study, we have a whole lot of families who all believe their common ancestor came from Co Wexford, but the paper trail for conventional genealogy research has dwindled away, or we suspect that John and James who emigrated to the US about the same time were brothers but there is no documentation to prove it – genealogical DNA studies can now be used to show whether its possible that two families (that are at the moment quite separate on paper) are actually related and have a common ancestor. And no, we don’t have to go digging up g-g-g-g-grandfather John to get his DNA – remember, he passed it on to his son, and his son’s son, and so on to the present day. So we find a living male descendant and they get their Y-DNA analysed. That gives us a pretty good indication of the genetic signature for the whole family tree (well, the male side, anyway). If we want to check it, we find a distant cousin of the first person who tested and get their DNA analysed. If its a very close match, then bingo – we know the Y-DNA genetic signature (and whats known as a haplogroup) for our whole family group.
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.

G6PD deficiency is a common genetic condition caused by defects in an enzyme called glucose-6-phosphate dehydrogenase, or G6PD. The G6PD enzyme helps protect red blood cells from damage. In people with G6PD deficiency, red blood cells are destroyed upon exposure to certain environmental triggers, which can lead to episodes of anemia. This test includes the most common variant linked to G6PD deficiency in people of African descent.


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 evaluated each kit by ordering one, just like any customer would, and tracking how long it took to arrive at the lab and to get processed. Then we compared the breadth and depth of the results to see what rose to the top. The whole process was a lot of fun, in part because of the anticipation of getting the results. Most of the kits warn that testing your DNA can lead to surprising—even life-changing—results. For example, there's the story of a woman who thought she was Irish, but her DNA test revealed she was also European Jewish, Middle Eastern and Eastern European. After diligent research, she discovered that her father, who had died years earlier, had been switched at birth with another child.
Prices range from £100 to £200 for a basic DNA profile, but it’s worth mentioning that the cost largely depends on what you intend to do with it. One of the major factors that you need to consider, and which significantly impacts the cost, is whether you want your DNA profile to be legally admissible or not. Legal DNA profiles cost more than peace of mind versions, but if there’s a chance that your profile will be used in legal proceedings, it’s worth paying extra for.
Following a recent case in Phoenix, in which a patient who had been in a coma for nine years gave birth, Arizona lawmaker David Livingston sponsored a senate bill that would require certain occupations to submit DNA samples along with fingerprints for use by law enforcement. Though Senate Bill 1475 has been updated since its initial draft, it could set a precedent that normalizes collection of DNA samples from everyone, not just those suspected or charged with a violent crime. 
Looking at your raw DNA file might not give you any useful information unless you’re looking for a specific marker. You can also upload the file into a third-party DNA databases for information or results beyond what’s available from your testing company. This process is not without risks, as your DNA testing company only ensures the security of your personal information in its own environment. Once you download the file, you’re responsible for the file’s security. However, uploading your raw DNA to a third party database isn’t inherently unsafe — just be cautious.
The trick for collecting a saliva sample is to give yourself plenty of time to create enough spit to fill your tube to the fill line (not including any bubbles). You should not eat or drink anything for at least an hour before collecting your sample, so it’s best to plan to collect your sample before eating. Our testers collected samples before lunch and found that thinking about the upcoming meal made saliva production easier, particularly as we collected multiple samples. Planning ahead and making sure you stay hydrated before you collect a saliva sample helps as well.

There are many things to think about when deciding whether genetic testing is right for you. Although these tests can provide important information about health risks, they can also be upsetting or raise questions about what the results mean. Genetic tests also have certain limitations that are important to understand. Your personal and family medical history, as well as your goals for testing, should all factor into your decisions about whether and how to test.

Each testing provider uses one of two methods to take your DNA sample and neither require blood. Family Tree DNA and MyHeritage DNA both use a cheek swab method where the user gently scrapes the inside of their cheek. The swab is then placed in a vial and sealed. AncestryDNA and 23andMe use a saliva sample. Some people may have a hard time producing a saliva sample so this should be taken into consideration when deciding on which test to choose.
Companies differ in terms of which reference populations they use. Some companies will create their own reference populations, while others will use populations identified in published studies. For example, 23andMe produce their own reference populations by sampling their customers (as long as the grandparents of those customers were all born in the same country). They then combine this data with public population data, produced by projects such as the Human Genome Diversity Project.
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.
And that’s where it starts getting interesting, because then we can start comparing that genetic signature to the results from other men who share the same surname but don’t appear on our family tree. If the matches are close, then we can start thinking “is there a common ancestor for these families another generation or two back? Are the families linked in some way?”. Depending on what we already know about either family group, it can help target the paper research to get those families linked, or take us back another generation or two.
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