Autosomes: Definition & Concept

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  • 0:00 Autosomes
  • 0:45 How Many Autosomes Do…
  • 2:15 What Do Human Autosomes Do?
  • 3:00 Lesson Summary
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Lesson Transcript
Instructor: Angela Lynn Swafford

Lynn has a BS and MS in biology and has taught many college biology courses.

An autosome is any chromosome that is not a sex-determining chromosome, so most chromosomes are autosomes. You can learn more about human autosomes in this lesson.


You have probably heard the term chromosome before, but do you know what it actually is? Chromosomes are made of DNA and contain genes or units of heredity. In some organisms, like bacteria, chromosomes have a circular shape. However, in most organisms that have a nucleus in their cells (this includes you), chromosomes are straight or linear.

Many animals, including humans, have two types of chromosomes: autosomes and sex chromosomes. Sex chromosomes are those that are needed for determining sex (male or female) of an individual. Autosomes are all the rest of the chromosomes that are not needed for sex determination. For the rest of this lesson, we will focus on autosomes.

How Many Autosomes Do Humans Have?

Humans have a total of 46 chromosomes in each body cell; 44 of these are autosomes. You get one set of 22 autosomes from your mom and another set of 22 from your dad. It is often easier to think about our autosomes in pairs because even though we have 44 autosomes, we actually only have 22 types. We have two copies of each type of autosome, one from each parent. Homologous chromosomes are two chromosomes of the same type, which are the same size and shape and have the same genes.

A picture or karyogram of all human chromosomes showing what each chromosome looks like. The autosomes are inside the red box and are labeled with numbers. The sex chromosomes are outside of the red box and given the letters X and Y. This karyogram is from a male because males have one X and one Y, while females have two X chromosomes.
Human Male Karyogram

Our paired autosomes are numbered 1 through 22. They are numbered according to size so that chromosome 1 is the longest, and chromosome 22 is the shortest. A picture called a karyogram is often used to look at our chromosomes. In a karyogram, homologous chromosomes are placed next to each other. For example, both copies of chromosome 1 are put side by side. Remember that you get one copy of each type of autosome from each of your parents.

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