DNA tests give you an educated estimate of your ethnic makeup and help inform genealogical research by verifying existing family trees and informing future avenues of investigation. Additionally, there's a possibility you'll find living DNA matches - distant cousins and other relations - who could share their family history with you to build a bigger picture of your family tree.

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.
Every company on this list promises test results in 6-8 weeks after they receive a sample, except for MyHeritage DNA which claims 3-4 weeks. This can vary however and is influenced by demand and other factors. It is generally a good rule of thumb to anticipate that it will take 2-3 months for results once you order a test. This accounts for the time it takes for you (or your recipient) to receive the test, provide a sample, mail it back and for processing of your results.
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.
Costs vary depending on the company you buy from. For example, the three most popular DNA ethnicity tests are undertaken by 23andMe, Family Tree DNA (FTDNA) and Ancestry.com. They all analyse autosomal DNA to report on your ethnic mix: 23andMe’s costs £149, FTDNA’s (named the ‘Family Finder’ test) costs £60 and Ancestry.com’s (named ‘AncestryDNA’) costs £79. However, it’s worth bearing in mind that 23andMe’s test also includes a Y DNA analysis and a mitochondrial DNA analysis, so if you’re interested in your paternal and maternal lineage (discussed below), this may be the more cost-effective choice!
The spit is for one of the home genetic-testing kits I’m sampling. A growing number of these kits (brands such as 23andMe, DNAFit, Thriva, MyHeritage DNA, and Orig3n) promise to unlock the mystery of your genomes, variously explaining everything from ancestry, residual Neanderthal variants, “bioinformatics” for fitness, weight loss and skincare, to more random genetic predispositions, denoting, say, the dimensions of your earlobes or the consistency of your earwax.
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.
We have zeroed in on autosomal tests only. These tests are used to give you the ancestry percentages and cousin matching most people are seeking. If you are interested in YDNA (paternal line only, for men) or mtDNA (maternal line only) you can find these tests at Family Tree DNA. 23andMe also offers limited motherline and fatherline results as part of this main ancestry test.
At-home paternity tests have been around much longer than other direct-to-consumer DNA tests. Most of them require you to collect cheek swab samples from a prospective father and child, which you then send off to a lab to determine paternity. For non-legal use, these tests can cost as little as $15, but tests that provide verified results that are admissible in court cost a few hundred dollars. 
In sexual reproduction in mammals the DNA in the sperm and egg joins up so that homologous sequences are aligned with each other. This is followed by exchange of genetic information to form a new recombined chromosome which is passed on to the offspring.  Cell division then takes place and the chromosomes are duplicated in the process of DNA replication, providing each cell its own complete set of chromosomes. The double-stranded structure of DNA provides a simple mechanism for DNA replication. In this process the two strands are separated and then each strand’s complementary DNA sequence is recreated by an enzyme.
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