Autosomal Recessive Inheritance

Autosomal recessive inheritance is marked by the primary feature that two copies of an altered gene located on one of the autosomes (that is, not the X or Y chromosomes) must be present for an individual to be affected with the trait or condition determined by that gene.

• An affected individual (homozygote) has two parents who are unaffected but each parent carries the altered gene (heterozygote).
• The risk of two heterozygotes, or carriers, having an affected child is 25%, 1 in 4, for each child that they have; similarly, there is a 3 in 4 chance that each child will not be affected .
• Males and females are at equal risk for being affected.
• Two affected individuals usually produce children all of whom are affected as well.

In addition to the basic interpretation of an autosomal recessive pedigree, Bayesian analysis can refine risk assessment by taking into account the full family and clinical information.