ARSACS Agenesis of the Corpus Callosum with Peripheral Neuropathy Autosomal Recessive Polycystic Kidney Disease Beta Thalassemia and Related Hemoglobinopathies Bloom Syndrome Canavan Disease Congenital Disorder of Glycosylation Type 1a (PMM2-CDG) Cystic Fibrosis D-Bifunctional Protein Deficiency Dihydrolipoamide Dehydrogenase Deficiency Familial Dysautonomia Familial Hyperinsulinism (ABCC8-Related) Familial Mediterranean Fever Fanconi Anemia Group C GRACILE Syndrome Gaucher Disease Type 1 Glycogen Storage Disease Type Ia Glycogen Storage Disease Type Ib Hereditary Fructose Intolerance Herlitz Junctional Epidermolysis Bullosa (LAMB3-Related) Leigh Syndrome, French Canadian Type Limb-Girdle Muscular Dystrophy Type 2D Limb-Girdle Muscular Dystrophy Type 2E Limb-Girdle Muscular Dystrophy Type 2I MCAD Deficiency Maple Syrup Urine Disease Type 1B Mucolipidosis Type IV Neuronal Ceroid Lipofuscinosis (CLN5-Related) Neuronal Ceroid Lipofuscinosis (PPT1-Related) Niemann-Pick Disease Type A Nijmegen Breakage Syndrome Nonsyndromic Hearing Loss and Deafness, DFNB1 (GJB2-Related) Pendred Syndrome and DFNB4 Hearing Loss (SLC26A4-Related) Phenylketonuria and Related Disorders Primary Hyperoxaluria Type 2 Rhizomelic Chondrodysplasia Punctata Type 1 Salla Disease Sickle Cell Anemia Sjögren-Larsson Syndrome Tay-Sachs Disease Tyrosinemia Type I Usher Syndrome Type 1F Usher Syndrome Type 3A Zellweger Syndrome Spectrum (PEX1-Related)
As stated at the start of this guide, each one of the main tests will provide you with easy-to-use reports and cousin matching that you can use in your genealogy research. You will need to carefully review the information provided in this guide to make a decision about which test is best for your particular needs. You may also choose to test with (or upload your results to) multiple companies.
Rather than simply looking at your DNA in isolation, the Findmypast DNA test analyses unique combinations of linked DNA. This proprietary method delivers a level of detail impossible with other ancestry DNA tests. It also uses the latest technology, which is constantly updated in response to the latest industry innovations and peer-reviewed research. As the technology evolves so too does the detail of your test results, which will receive free ongoing upgrades.
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.  
Home DNA testing has gone from a niche pursuit to a simple way to map out your family tree. A DNA test can be used to determine paternity and research ancestry or familial origin. And over the past few years, they've become quite affordable, with a wide range of companies selling DNA test kits -- from trailblazers such as Ancestry and 23andMe to upstarts that include LivingDNA. 
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.
Consult a doctor on any health data: Cancer. Leukemia. Heart disease. Alzheimer's. There are a lot of scary afflictions out there, and your DNA testing may well indicate which ones to which you are genetically predispositioned. But the data from DNA testing exists in isolation. You should consult your doctor to explore the data from any of these tests. They'll help you determine how to implement any lifestyle changes or followup testing as a result, if it's worth doing so.
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.
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.
Next, you'll receive an email alert that your results are ready, and that's when the fun begins. Your results may not be as dramatic as those portrayed in TV ads, but you may find some surprises. One important note: Results are different for women and men. Women, who have the XX chromosome, can only trace back the maternal line. Men, having the XY chromosome, can track back the maternal and paternal line, painting a complete picture. If you're a woman, it's worth asking your brother, if you have one, to take a test and share the results. When some of these services ask for your sex when you order your kit, they simply want to know about your chromosomes.
Similarly, if a person has contributed a clear and distinct minority of the DNA detected, that part of the profile may be referred to as the “Minor Contribution”. However, if DNA from one or more people is present in a mixed DNA result in roughly equal quantities, any statistic relating to the likelihood that any one particular person may have contributed to the DNA profile is necessarily reduced in value due to the inherent uncertainties regarding which DNA components may have come from either contributor.

In Newman’s view, the genie is out of the bottle with home genetic-testing kits. He says that while the kits could potentially provide data in the future, right now, they lack “clinical utility” – they look at genetic variants that, individually, have a very low chance of predicting specific health risks, as there are too many variables: “It’s like the Opportunity Knocks clap-o-meter, with some people further along the scale, and therefore more likely to get the condition and then people at the other end of the scale, who are unlikely to get it.”

“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?”

Some services include shipping costs in the cost of the kit; AncestryDNA's $99 fee includes two-way shipping. National Geographic's Genographic Project ships the kits for free, but you have to purchase postage when you send your kit to their lab. 23andMe tacks on a two-way shipping fee of $9.95 for the first kit and $5 for each additional one. HomeDNA includes a prepaid envelope to return your sample and offers three shipping options: $7 for two-day shipping, $14 for overnight, and free shipping that takes 7 to 12 business days. Finally, MyHeritage charges $12 for shipping; if you order two kits, you pay $6, and if you order three or more, you get free shipping.

By comparing the arrangement and distribution of the peaks, it is possible to compare profiles of known origin with a profile from a crime sample. If the two profiles match, databases are used to estimate the probability of obtaining a matching profile from a person selected at random; this is referred to as thematchprobability. Closely related individuals are more likely to share DNA profiles than more distantly related individuals.
23andMe has also been the target of concerns over how they handle user data. Their tools are more advanced than what AncestryDNA offers, and the International Society of Genetic Genealogists claims that they have the most accurate admixture results – but many in their database are health testers and may not be receptive to matching for genealogy purposes. They also offer no family tree integration at all.
Is this a perfect method?  No, but it’s a good way to get a general idea about where your ancestors were from.  Genealogical DNA tests can tell you a lot about your ancestry going back 300-500 years in time, for the most part.  They can also tell you a little bit about your ancestry going even further back.  This is why comparing your DNA to those whose families have stayed in a particular area for a long time is a fairly accurate way to perform the estimate.
As it happens, most of the data on 23andMe seems harmless and fun. There are the “Neanderthal variants” (I have fewer of them than 58% of 23andMe customers, thank you very much), the bizarre earwax/earlobes-type data and, apparently, I have the muscle composition generally found in “elite athletes” (fancy). On the downside, my lineage isn’t as exotic as I’d hoped: 99.1% north-western Europe, of which 71% is British/Irish, with just 0.01% “Ashkenazi Jewish” to offset the genetic monotony. At £149, the 23andMe kit isn’t cheap and I’m quite tempted to demand a recount.
AncestryDNA, 23andMe, HomeDNA, Living DNA, and MyHeritage DNA all provide reports of your ethnicity, some showing maps of where your ancestors lived along with information about the particular countries and regions. National Geographic goes further back, pinpointing where in Africa your ancestors came from and tracing migration patterns through to near-present times. It's less about your personal genetic makeup and more about who your ancestors were and how you're connected to the beginning of civilization.
I’ve tested with each of the big five. It’s wise in the sense that you have access to every database of matches. Some companies allow you to upload your raw DNA that was generated from other testing companies. That can save you a lot of money. So you can test with Ancestry, then upload your raw DNA to MyHeritage, FTDNA and LivingDNA. 23andMe do not allow uploads right now so you’d have to test with them separately. Ancestry also does not allow uploads, that’s why I would use them to do your initial test.
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.
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.