Autosomal DNA (Definition)

Updated May 28, 2019

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General interest in DNA tests is exploding in popularity. These range from providing insights about genetic health predispositions to DNA testing for ancestry.

What's in this Guide?

Disclaimer: Before You Read

It is important to know that your genes are not your destiny. There are various environmental and genetic factors working together to shape you. No matter your genetic makeup, maintain ideal blood pressure and glucose levels, avoid harmful alcohol intake, exercise regularly, get regular sleep. And for goodness sake, don't smoke.

Genetics is a quickly changing topic.

One recent breakthrough is autosomal DNA testing, which checks your autosomal chromosomes — the other 22 pairs besides your X and Y chromosomes.

While it is possible to discover genetic traits and health predispositions with this form of testing, there are other more efficient DNA tests to discover your particular DNA structure for medical issues. So the science behind autosomal DNA is primarily used for understanding your family tree.

We have researched the various aspects of autosomal DNA research and testing to give you a comprehensive picture.

What Is Autosomal DNA?

A definition of autosomal DNA (atDNA) will not be clear unless you first have a basic understanding of DNA and chromosomes.

DNA is short for Deoxyribonucleic acid. This is a molecule with two chains that create a double helix (because they coil around each other).

The DNA carries genetic instructions and provides information on how an organism should grow, develop, function, and reproduce.

Each cell has a nucleus. In the nucleus, the DNA is organized into chromosomes, structures that look like threads.

Each chromosome is coiled around histones, which are proteins that support this structure. Each cell has 23 pairs of chromosomes. So, each cell has a total of 46 chromosomes.

Humans inherit two classes of chromosomes: One is the sex-linked X chromosome and the Y chromosome. Males have a Y chromosome and an X chromosome.

Females have two X chromosomes. The other 22 chromosome pairs are the autosomal chromosomes.

Once you understand these concepts, you can simply yet accurately define autosomal DNA as chromosomes in DNA that are not the sex chromosomes.

The Function of Autosomal DNA

Apart from its biological function to provide genetic information for an organism, the autosomal DNA can be used to provide information about to help you trace your genealogy.

Since your autosomal DNA is equally inherited from both your parents, researchers can describe the genealogical relationship between two people by how much autosomal DNA they have in common. So, for example, if you are related to someone but don’t know much about them or your relationship, you will be able to understand the extent of your genetic connection based on the autosomal DNA you share with them.

How Can You Test for atDNA Using DNA Tests?

To get started with autosomal DNA testing, you must order a testing kit from a DNA direct-to-consumer genetic testing laboratory.

This type of testing is as simple as sending the cells from a cheek swab or from saliva expressed into a test kit tube to a DNA research company. After they get your DNA from the cells in your sample, they will use their proprietary algorithm to evaluate matches in their autosomal DNA database to calculate the most probable relationships.

This type of testing does more than identify relatives you already know. It also informs you about distant relationships, including those from different ethnicities, cultures, or countries.

For best results, you should use at least three different direct-to-consumer genetic testing companies. Since they all use different algorithms and databases, you will get a much broader understanding of your genealogy.

Types of Genealogical DNA Tests

There are three basic types of genealogical DNA tests:

  • An Autosomal and X-DNA test. This looks at your X chromosome and chromosomes numbered 1 to 22, which you inherit from both your parents as well as your recent ancestors. In comparison to a Y-DNA test and an mtDNA test, an Autosomal DNA test allows you to trace both male and female lines of your family. This test can also be taken by both men and women. Although this test is broader than a Y-DNA and mtDNA tests, it does not go as deeply into the details of your relationship with other people.
  • A Y-DNA test. This is a Y chromosome test and it can only be taken by men because women don’t have Y chromosomes. It investigates your patrilineal ancestry, the heritage from your father’s side of the family.
  • An mtDNA test. An mtDNA test is a mitochondrial DNA test that can be taken by both men and women since both have mitochondria. It investigates your matrilineal ancestry, the heritage from your mother’s side of the family.

Two Types of Autosomal DNA Tests

One type of autosomal DNA test is testing yourself. This will give you matches from both your mother and father’s side of your family.

Another type of autosomal DNA test is testing your parents. You will get more matches this way then if you only test yourself. By testing your parents, you will now be able to explore both the patrilineal and matrilineal relationships.

What Does Autosomal DNA Tell Us?

An autosomal DNA test tells us about living cousins, our ethnic ancestry, and possible genetic health traits.

Living Cousins

Autosomal DNA tests will tell you a great deal about at least five generations of your ancestry. Autosomal DNA statistics become less reliable past five generations and can result in DNA false positives 1 about relationships.

You have 32 great-great-great grandparents. These 16 couples probably had one or more children.

Since many of these children probably got married, they had more children. As a result of all this branching out of relationships over five generations, you may have thousands of cousins, many of them still alive.

When you take an autosomal DNA test and some of your cousins from unknown branches of the family tree have also taken the test, you can be introduced to them.

Ethnic Ancestry

You will be able to get an overall understanding of your ethnic ancestry to understand what percentage of your ancestors were European, African, or Asian.

Genetic Health Traits

Although a genealogical DNA test is not intended to determine any genetic health traits, this type of information can surface. You may, for instance, learn about a distant relative who had a genetic disease.

By extrapolating autosomal DNA statistics, you might then conclude that you could be a healthy carrier of this disease. On the bright side, you may discover you belong to a haplogroup — a group that shares a common patrilineal or matrilineal ancestor — that has a history of longevity.

Why Has Autosomal DNA Become so Important?

Autosomal DNA can help raise self-awareness about your identity. As a result, you may be able to form all kinds of wonderful relationships with those who share your family line.

Here are some things you might discover:

  • You are related to a famous historical figure.
  • You have different ethnic roots than you knew.
  • You have living cousins who would love to meet you.

Is Autosomal DNA Inherited From the Mother or Father?

Your DNA is inherited from both your parents, who, of course, got their DNA from each of their parents, and so on.

How Autosomal DNA Is Transmitted

While you inherited your DNA directly from your parents, it is a mixture of the DNA that they got from their parents and on up the line. Although this DNA mixing occurs randomly, long DNA blocks stick together for many generations.

Genetic Health Conditions Related to Changes in atDNA

Although autosomal DNA testing can reveal genetic health conditions, it is usually an accidental discovery. If you are interested in determining genetic health conditions, you should take medical DNA tests 2.

These tests are far more focused in their inquiry and can reveal general and specific health risks, reveal if you are a healthy genetic carrier, reveal your wellness traits, and even reveal your rate of cellular aging (which helps to predict longevity).

5 Health Conditions Related to atDNA

We inherit genes in specific ways from our parents, and one of these ways is autosomal recessive inheritance 3, a disease-carrying gene in one of the chromosomes. If you only carry one gene, then it is a recessive gene and you are a healthy carrier. However, if your partner also has the same recessive gene then when you have a child, he or she might get both copies of the gene and have the genetic disease.

Autosomal DNA Diseases

Five examples of autosomal recessive diseases are Tay-Sachs disease 4, Sickle Cell Anemia 5, Cystic Fibrosis 6, Fanconi Anemia, and Hartnup's Disease.

  • Tay-Sachs disease results in brain and spinal cord nerve cell destruction. Infantile Tay-Sachs, the most common type, affects babies in their first 3 or 6 months, and they lose their ability to sit or crawl.
  • Sickle cell anemia affects red blood cells, making them rigid and shaped like crescent moons. These distorted, sticky blood cells can’t carry enough oxygen to nourish the body.
  • Cystic fibrosis affects both the lungs and the digestive system. Sticky mucus clogs the lungs and prevents the pancreas from working properly. The disease is life-threatening and those with it tend to have shorter lives.
  • Fanconi anemia affects a person’s bone marrow and decreases blood cell production.
  • Hartnup disease affects the absorption of certain amino acids. For instance, insufficient tryptophan absorption compromises the secretion of serotonin and melatonin.

AtDNA’s Role in Genealogical Research, Explained

Autosomal DNA testing checks single nucleotide polymorphisms (SNPs), which are often described as pairs of locations in autosomal DNA. You may have as many as 700,000 such pairs in your autosomal DNA.

When researchers look at your autosomal DNA, they can compare it to other people in their database who have identical sections with numerous common SNPs. Based on this information, they can trace common ancestors.

If the matching sections are short, it might be a coincidence, but if they are long, it is statistically significant enough to help them figure out how close your DNA is to certain people in their database.


You can discover your unique genetic story through autosomal DNA testing. By getting a biogeographical analysis of your ancestry, you will be able to get a broad overview of your ancestry.

It is also possible that genealogical matching will help you discover living cousins and create new relationships. Places like GEDmatch make it easy to collaborate with other people who tested at other direct-to-consumer genetic testing companies, and you will be able to access even more genetic tools to make sense of your autosomal DNA statistics.

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Referenced Sources

  1. False-positive results released by direct-to-consumer genetic tests highlight the importance of clinical confirmation testing for appropriate patient care
    Stephany Tandy-Connor MS, Jenna Guiltinan MS, Kate Krempely MS, Holly LaDuca MS, Patrick Reineke BS, Stephanie Gutierrez BS, Phillip Gray PhD & Brigette Tippin Davis PhD, FACMG 22 March 2018.
  2. Genetic testing
    Learn how genetic testing can help determine the likelihood of your patients passing on or inheriting certain medical conditions or diseases
  3. Autosomal recessive inheritance pattern
  4. The natural history of juvenile or subacute GM2 gangliosidosis: 21 new cases and literature review of 134 previously reported.
    Maegawa GH1, Stockley T, Tropak M, Banwell B, Blaser S, Kok F, Giugliani R, Mahuran D, Clarke JT.  Pediatrics. Nov 2006. Epub 2 Oct 2006.
  5. Sickle Cell Anemia
    Gael J. Lonergan, David B. Cline, Susan L. Abbondanzo. 1 Jul 2001.
  6. About Cystic Fibrosis