Autosomal recessive disorders are genetic conditions that manifest only in individuals who inherit two copies of a specific gene located on a nonsex chromosome, known as an autosome. These individuals receive one copy from each parent. The parents themselves are carriers, having one copy of the recessive gene and one normal gene, so they do not show symptoms of the disorder. When both parents are carriers, there is a 25% probability that their child will inherit both copies of the recessive gene and develop the disorder. There is a 50% chance that the child will inherit one recessive gene and become a carrier like the parents, and a 25% chance that the child will inherit two normal genes.An example of such a disorder is cystic fibrosis (CF). A child with CF has inherited the CF gene on both chromosome 7s, making them homozygous for CF. The parents, each carrying one CF gene and one normal gene, are heterozygous for the condition. Other examples of autosomal recessive disorders include Canavan disease, a neurological condition; thalassemia, a blood disorder; Ellis-van Creveld syndrome, associated with fever and pain episodes; Fanconi anemia, a serious blood disorder with a heightened risk of cancer; Gaucher disease, prevalent among Ashkenazi Jews; mucopolysaccharidosis, a group of carbohydrate storage disorders; phenylketonuria (PKU), a metabolic disorder screened for in newborns; and sickle cell disease, the most common genetic disorder among African Americans.
