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.
Admixture percentages are one of the biggest reasons people choose to have their DNA tested. This report attempts to accurately match your DNA with population samples from around the world to tell you where your ancestors came from. Each of these companies has strengths and weaknesses when it comes to this calculation, and in the reports it provides to users.
There is one really, really important thing to know about this estimate, however.  Each child inherits 50% of their DNA from each parent.  That means that 50% of their parents’ DNA does NOT get passed down to the child.  This can mean that a child of a 100% Eastern European person will only show 50% Eastern European DNA, and their grandchild will only show 25%, and their great-grandchild 12.5% – in a perfect scenario.
So you probably have answered this already and I have no idea. I’m just trying to dumb it down for myself. Really great info not overloaded with the information. I’m trying to do a ancestor tree. I have the names all the way back to 1900 on my dads and moms direct line. I was wandering what test would be best to take to find out more exact answers on bloodline and names in my family all the way back to 1700-2000?
There is one really, really important thing to know about this estimate, however.  Each child inherits 50% of their DNA from each parent.  That means that 50% of their parents’ DNA does NOT get passed down to the child.  This can mean that a child of a 100% Eastern European person will only show 50% Eastern European DNA, and their grandchild will only show 25%, and their great-grandchild 12.5% – in a perfect scenario.
The situation is made even more complex if it is considered that three or more people may have contributed to a particular DNA result. Often, in such cases, it is not possible for a scientist to undertake a reliable statistical evaluation of the mixed DNA result. If the DNA result indicates that a very low level of DNA has been detected, it is recommended that the reporting forensic scientist consider the possibility that the result may have been derived from a very low level of DNA from more than one person, some of the components of which may be missing from the DNA result because of the low level of DNA present
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.
AncestryDNA has the largest database to compare your results to when making matches, with 23andMe coming in second and FTDNA in fourth. MyHeritage DNA, although newer than the others, is catching up fast and numbers now surpass FTDNA. Current numbers can be seen in the chart above and are estimates based on available data. Each of these databases is growing, some of them quite rapidly.

For these reasons, mapping segments of your autosomal DNA to whole continents can be determined with a high level of certainty, but when you try to attribute these segments to specific tribes, regions or even countries, the certainty decreases. This is why some genetic ancestry companies will attribute a proportion of your DNA to areas such as ‘Eastern Europe’ or ‘Southern Asia’, instead of to specific countries.
Family Tree DNA (the longest running testing company) offers a well-established database of “cousins” and advanced tools for exploring your results. MyHeritage offers the ability to sync your results with your family tree research in a very unique way. Both are a good choice, but since every person’s needs are unique we suggest you read the full guide before deciding.

Doing an DNA test without any research can be extremely disappointing - as there are many geographical regions not represented in some DNA kits. This can cause a disconnect or very inaccurate reporting. Beyond ancestry tests, there are companies that recommend wines or exercise regimens based on your DNA. With all the available options, it’s easy to default to a recognizable name, which isn’t necessarily bad. But certain tests do specific things better. Our goal is to match your expectations with the test that fits best. 
Three of the companies, MyHeritage, Ancestry and FTDNA, use the Illumina OmniExpress chip and 23andMe uses the new Infinium® Global Screening Array chip from Illumina. The fact that all of the chips come from the same company may be confusing, leading some to believe that all tests are created equal. This is not the case. The chip used to process DNA samples is only one part of the process. Each company develops their own analysis of the results, references different population samples and provides different reports. In addition, each one of these DNA test providers offers different tools for you to analyze the data you receive, creating variations in results, accessibility and usefulness.

DNA fingerprinting is commonly used to compare DNA samples taken from the crime scene with those taken from suspects, to either prove or disprove their innocence. In the UK, 10 markers are analysed to produce DNA profiles from the samples taken in criminal investigations. These are then compared to (and stored in) the National DNA Database (NDNAD) to identify if there’s a match. This database currently contains DNA profiles for 10% of the UK population, along with the individuals’ names and ethnicities. Anyone who’s been arrested for a recordable offence has their information recorded on the database, unless they are found innocent or not charged – in these cases, the individuals’ biological samples and corresponding information is destroyed within six months of sample collection.
A few of the DNA tests we tested, including the National Geographic Geno 2.0, use genetic sequencing instead of genotyping. Sequencing is newer in the mainstream direct-to-consumer DNA testing market, as it used to cost more and take much longer to sequence a person’s DNA. Sequencing identifies the exact makeup of a certain piece of DNA – be it a short segment or the whole genome. The Helix tests sequence the Exome, which are the parts of the genome responsible for protein production, plus several other regions of interest. 
Therefore, when the markers in two samples are analysed, the number of times that they’re repeated can be compared and the statistical likelihood that they came from the same person or from two closely related individuals can be calculated. This is why DNA profiling can be used to establish biological relationships, as well as to connect DNA evidence with a criminal suspect.

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.
What we would expect to find then in this example is that the two descendants of John show a very close match, and the two descendants of James also show a very close match (because we know from conventional paper based research that they are related). If all four match very closely, then that’s further evidence to add to our theory that John and James were really brothers. Not conclusive proof- but pretty solid evidence.