Glossary

An autosomal recessive disorder is a single gene disorder that is inherited as a recessive allele on an autosome (non-sex chromosome). As a result, males and females can both serve as carriers for the condition without being afflicted, which is illustrated in the figure below, in which the offspring of two heterozygous $\mathrm{Rr}$ individuals has a 1/4 probability of inheriting the condition (and a 1/2 probability of becoming a carrier themselves, along with a 1/4 probability of being completely healthy).

Many single-gene disorders are autosomal recessive, like cystic fibrosis.