A carrier is a person who can pass an inherited (genetic) disease on to his or her children but does not have the disease. The person can also pass on carrier status.

Some diseases are caused by defects in a person's genes or chromosomes. Each person inherits 23 chromosomes from each parent and so has 23 pairs of chromosomes. One or both of the chromosomes in a pair may be damaged or defective in a way that causes an inherited (genetic) disease.

In some cases both chromosomes in a pair must be defective for the person to have the disease. This is known as an autosomal recessive disease. If only one of the chromosomes in the pair is affected, the person may be a carrier.

Some genetic disorders are caused by defects in the X and Y chromosomes, which determine a person's gender.

Last Updated: November 4, 2009

Author: Maria Essig

Medical Review: Kathleen Romito, MD - Family Medicine & Siobhan M. Dolan, MD, MPH - Reproductive Genetics

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