Definition of Autosomal recessive

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Autosomal recessive: A genetic condition that appears only in individuals who have received two copies of an autosomal gene, one copy from each parent. The gene is on an autosome, a nonsex chromosome. The parents are carriers who have only one copy of the gene and do not exhibit the trait because the gene is recessive to its normal counterpart gene.

If both parents are carriers, there is a 25% chance of a child inheriting both abnormal genes and, consequently, developing the disease. There is a 50% chance of a child inheriting only one abnormal gene and of being a carrier, like the parents, and there is a 25% chance of the child inheriting both normal genes.

Cystic fibrosis (CF) is an example of an autosomal recessive disorder. A CF child has the CF gene on both chromosome 7's and so is said to be homozygous for CF. The parents each have one CF and one normal paired gene and so are said to be heterozygous for CF.

Other examples of autosomal recessive disorders include:

• Alport syndrome, a form of nephritis, a kidney disease
• Canavan disease of the brain
• Congenital neutropenia, a blood condition
• Ehlers-Danlos syndrome, a connective tissue disease
• Ellis-van Creveld syndrome, a birth defect
• Familial Mediterranean fever with attacks of fever and pain
• Fanconi anemia, a progressive blood disorder with a high risk of leukemia
• Gaucher disease (a common genetic disease of Jews
• Mucopolysaccharidosis (MPS), a series of carbohydrate storage disorders
• Osteogenesis imperfecta (brittle bone disease)
• Phenylketonuria (PKU), a disease for which newborns are tested
• Sickle cell disease. the most common genetic disease in Blacks