Loss-of-function mutations in one X-chromosomal (FANCB) and at least twenty autosomal recessive genes (FANCA to RFWD3/FANCW) as well as missense mutations in one dominant negative FA gene (RAD51A/FANCR) result in the typical defects associated with FA (13–15). The gene discussed is RFWD3; the disease is Friedreich ataxia.