An autosomal DNA test measures your autosomal chromosomes, which are the chromosomes that make up the lion’s share of your DNA.

Autosomal DNA tests have the ability to analyze the DNA from more of your relatives than other DNA tests. For instance, an autosomal DNA test can find genetic information about your grandfather, which other tests typically can’t do.

Autosomal DNA tests are the most information-rich tests available. These tests can find relatives, from long-lost siblings to 10th cousins, and tell you where your ancestors may have lived, from 500 to more than 1,000 years ago.

What Is Autosomal DNA?

DNA comes in long stretches called chromosomes and people typically have 23 pairs of chromosomes for a total of 46. There are two broad categories of chromosomes—autosomal and sex chromosomes. Sex chromosomes are made up of X and Y chromosomes and people typically have either a pair of X chromosomes or X and Y chromosomes. 

Autosomal chromosomes make up the other 22 pairs and most everyone has a complete set of these. An autosomal DNA test only looks at the DNA from these 22 chromosome pairs.

How Does Autosomal DNA Testing Work?

Autosomal DNA tests look at the autosomes, the 22 pairs of chromosomes that most everyone has. The most common method is to use a DNA array to look at hundreds of thousands of positions, or markers, across all 22 pairs.

Scientists can use this information to look for large areas of shared DNA between you and other people in a database to find close relatives. The more DNA shared between you and another person, the more closely you are related.

Scientists can also compare your DNA to DNA from people with deep roots in various parts of the world. For example, if part of your DNA is similar to the DNA of people from France, that part of your DNA is said to be from France. This is how we learn where your ancestors lived hundreds or even a thousand or more years ago.

Autosomal DNA tests provides greater genetic information compared to Y-DNA and mitochondrial DNA (mtDNA) tests, which cannot reveal as much information about close relatives or recent ancestry.

Is Autosomal DNA Testing Accurate?

An autosomal DNA test is particularly useful for finding both close and distant relatives. An autosomal DNA test identifies all your second cousins and most of your third cousins. The chances of finding additional more distant relatives can be lower, but it can still be possible to find even a tenth cousin.

Other DNA tests such as Y-DNA tests or mtDNA tests are less suitable to find distant relatives because they focus exclusively on a single branch of your family tree. They can be useful for determining if you are related to someone on your dad’s male line or your mother’s female line, but they cannot determine exact relationships. In fact, the DNA looked at in these tests is shared with enough people that they cannot truly be confirmatory in establishing a relationship.

Who Should Take an Autosomal DNA Test?

An autosomal DNA test kit is suitable for people who are curious about where their ancestors might have lived 500 to 1000 years ago or are interested in finding existing family members. AncestryDNA® also offers the possibility of learning more about past family migrations and communities through its patented Genetic Communities™ technology. This uses family trees and historical records to find genetic communities that you may have a connection to.

The autosomal DNA test provides results that are more relevant to recent family connections than either mitochondrial DNA (mtDNA) or Y-DNA
tests, because it considers genetic information that you share with all members of your family. While a Y-DNA test traces only paternal lineage, and a mtDNA test traces matrilineal (mother’s female) ancestry, an autosomal DNA test will yield meaningful results to everyone.

Autosomal DNA tests are available to anyone, regardless of gender, and provides information about your recent genetic history. It can also be a great way to find new family members within a few generations. With AncestryDNA®, there have been countless stories of people finding distant cousins they never knew existed.