Autosomal dominant and autosomal recessive ataxias are hereditary ataxias, and spinocerebellar ataxia (SCA) and Friedreich’s ataxia (FRDA) are the most common forms of hereditary ataxia. Autosomal dominant genes express themselves when present. Autosomal recessive genes will only express themselves when in the homozygous state — i.e., both genes in the gene pair are the recessive gene form. Thus, recessive genes can be “carried” by those whose phenotype does not exhibit the gene characteristic, while dominant genes cannot be “carried”. Therefore, generally autosomal dominant ataxias are easier to express and at a higher morbidity than autosomal recessive ataxias.