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Chromosome 22
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Chromosome

Chromosome 22

Chromosome 22 is the second smallest human chromosome, notable for being the first to be fully sequenced. Changes in its structure or number are linked to a range of health conditions, from developmental disorders to specific cancers.

Overview

Humans normally have 46 chromosomes (23 pairs) in each cell. Two copies of chromosome 22, one copy inherited from each parent, form one of the pairs. Chromosome 22 is the second smallest human chromosome, spanning more than 51 million DNA building blocks (base pairs) and representing between 1.5 and 2 percent of the total DNA in cells.

In 1999, researchers working on the Human Genome Project announced they had determined the sequence of base pairs that make up this chromosome. Chromosome 22 was the first human chromosome to be fully sequenced.

Identifying genes on each chromosome is an active area of genetic research. Because researchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. Chromosome 22 likely contains 500 to 600 genes that provide instructions for making proteins. These proteins perform a variety of different roles in the body.

Health Conditions Related to Chromosomal Changes

The following chromosomal conditions are associated with changes in the structure or number

Frequently Asked Questions

Many conditions linked to chromosome 22 changes can be inherited in an autosomal dominant or recessive pattern, or they can arise spontaneously (de novo) in an individual. The specific inheritance risk depends on the exact chromosomal change and whether a parent is a carrier. Genetic counseling is crucial to understand the specific inheritance pattern and recurrence risk for future pregnancies.
Management is highly individualized and focuses on addressing specific symptoms and developmental needs. This often includes early intervention therapies (physical, occupational, speech), specialized education, regular medical monitoring for associated health issues (like heart or kidney problems), and sometimes medication for symptoms like seizures. Support groups can also be very beneficial for families.
Early warning signs can vary widely depending on the specific genetic change. However, common indicators might include developmental delays (e.g., in speech or motor skills), distinctive facial features, heart defects, feeding difficulties, or intellectual disability. For some conditions, specific cancers may develop later in life.
Diagnosis typically involves genetic testing, such as a karyotype to look at the overall chromosome structure, a chromosomal microarray (CMA) to detect smaller deletions or duplications, or specific gene sequencing if a particular gene on chromosome 22 is suspected. These tests are usually performed on a blood sample.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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