Friedreich's ataxia is an autosomal recessive disease, which means the patient must inherit two affected genes, one from each parent, for the disease to develop. A person who has only one abnormal copy of a gene for a recessive genetic disease such as Friedreich's ataxia is called a carrier. A carrier will not develop the disease but could pass the affected gene on to his or her children. If both parents are carriers of the Friedreich's ataxia gene, their children will have a 1 in 4 chance of having the disease and a 1 in 2 chance of inheriting one abnormal gene that they, in turn, could pass on to their children. About one in 90 Americans of European ancestry carries one affected gene.
Humans have two copies of each gene - one inherited from the mother and one from the father.
Genes are located at a specific place on each of an individual's 46 chromosomes, which are tightly coiled chains of DNA containing millions of chemicals called bases. By combining in long sequences, like long phone numbers, the paired bases tell each cell how to assemble different proteins. Proteins make up cells, tissues, and specialized enzymes that our bodies need to function normally. The protein that is altered in Friedreich's ataxia is called frataxin. In 1996, an international group of scientists identified the cause of Friedreich's ataxia as a defect in a gene located on chromosome 9.