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.

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The technique of DNA profiling was developed by Alec Jefferys in the mid-1980s and is based on the analysis of markers in DNA known as microsatellites or Short Tandem Repeats (STRs). These markers are found at specific points (also called loci) in everyone’s DNA and they’re motifs of two-six bases (the units that make up our genes) that are repeated numerous times. The exact number of times these markers are repeated differs between individuals, but members of a family will share the same or a similar number of repeated markers, depending on how closely related they are.
If you opt in to 23andMe’s family matching feature, you can connect with other 23andMe users with similar genes. This feature lets you view your matched relative’s display name, sex, profile photo, percent of DNA shared, number of DNA segments shared, relatives in common and haplogroups. The interface also estimates how closely you are related to each match. It’s very easy to connect with your matches on the website, and you can request more information by inviting them to share DNA reports.
Autosomal DNA Tests: These type of tests have become extremely popular over the last couple of years as prices have dropped and the amount and accuracy of the results has increased. Autosomal testing looks at information across the genome to provide clues to our personal ancestral history on a much broader scale than either mtDNA or Y-DNA testing can. While this type of genetic testing is an ever evolving science, you can expect to get a general breakdown of your ancestors’ geographical origins (your admixture) as well as connections with people who share your ancestry. This can be a unique and exciting way to tear down those brick walls and uncover branches of your family tree you never knew you had. For some, the results can be surprising and enlightening–for others, there can be a simple verification of already known information and even some disappointment in discovering nothing new.