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.
