When STR profiling is carried out, the whole of the person’s DNA is not examined. Rather, specific regions (loci) of the DNA which are known to vary greatly between individuals are examined. These loci are areas of the DNA which contain varying numbers of repeating sequences known as short tandem repeats (STRs). It is the number of these repeating units which can differ between individuals. If there are differences between profiles obtained from different samples, the two samples cannot have come from the same person. If, however, the profiles match, then it follows that the samples could have originated from the same person or from any other person who happened to have the same STR profile.Â
After collecting spit and cheek cells, we mailed all of the tests at the same time and waited for results, noting all communications from the company in the meantime and how long it took each service to notify us that results were ready to view. We collected data based on testers’ impressions of their results, each service’s features and extras, how easy it was to use and navigate the service’s website, along with several other factors. We added this testing data to rigorous research and information gleaned from conversations with representatives from Ancestry, 23andMe, MyHeritageDNA, LivingDNA, Humancode (now owned by Helix) and 24genetics. 
Each of the kits work similarly: You answer a few questions about yourself, order the kit, collect your sample, register the kit (this is very important), send it back, and wait for the results. That said, they differ in the collection process and, to a smaller extent, the cost of shipping. When we tested 23andMe back in mid-2015, the company was unable to accept DNA samples collected in or sent from New York State, because of local laws (we had to cross the border to New Jersey). The company was also prohibited from shipping DNA kits to Maryland.
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.

This is the ‘Out of Africa’ theory, and it’s reflected in our DNA which shows that we’re all descended from ‘Y chromosomal Adam’ (our earliest common male ancestor) and ‘mitochondrial eve’ (our earliest common female ancestor). Our DNA can also show us the migratory paths that our ancestors took after leaving Africa in the intervening millennia, to get to where they settled in the thousand year period before the era of mass migration circa 1850.
These tests can reveal the migratory paths of your paternal and maternal ancestors after they left Africa 200,000 years ago. By studying the migratory route they took, this can help you identify the ethnic groups they may have been part of. That said, as your paternal line is your father’s father’s father etc., and as your maternal line is your mother’s mother’s mother etc.; your paternal and maternal ancestors represent a smaller and smaller proportion of your ancestry the further back you go (just one sixteenth of your total ancestry five generations ago). Therefore, tracing your migratory paths back thousands of years may provide insights, but they’re a poor means of exploring your ethnic mix.
Even though we are all unique, most of our DNA is actually identical to other people’s DNA. However, specific regions vary highly between people. These regions are called polymorphic. Differences in these variable regions between people are known as polymorphisms. Each of us inherits a unique combination of polymorphisms from our parents. DNA polymorphisms can be analysed to give a DNA profile.
If you’ve already taken a test with another company, MyHeritage lets you upload your raw data to its database for free. This feature is particularly useful if you’re looking for lost relatives, as you can pay slightly more for one test with Ancestry or 23andMe, which have larger databases, but still access MyHeritage’s database as well, which has 1.75 million users as of October 2018.
DNA is found in most cells of the body, including white blood cells, semen, hair roots and body tissue. Traces of DNA can also be detected in body fluids, such as saliva and perspiration because they also contain epithelial cells. Forensic scientists and Police officers collect samples of DNA from crime scenes. DNA can also be collected directly from a person using a mouth swab (which collects inner cheek cells). Find out more in the article Crime scene evidence.
“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?”
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.
1. Family Tree DNA’s Family Finder: One of the first to offer these types of tests, FTDNA is generally considered the leader in autosomal DNA testing for ancestry and provides some of the best tools available for genealogists. Their population finder section is currently a bit less specific than the other companies, but FTDNA Family Finder users are eagerly awaiting a much improved update to be released sometime in the next month. Find out about Family Finder here.