Each half of a chromosome pair is similar to its partner, except for one pair, which features two X chromosomes in females and one X and one Y chromosome in males. This determines the sex of the individual. This means that men and women are at equal risk of inheriting the disease. Back to Top Genes may be either dominant or recessive. Dominant genes need only be present in one chromosome of a pair to produce a gene's particular trait or characteristic.
Recessive genes require a chromosomal match from both parents to produce a given trait.
Because HD is an autosomal dominant disorder, only one copy of the defective gene, inherited from either parent, is needed to produce the disease. A child who does not inherit the HD gene will never develop the disease and cannot pass it on to his or her offspring. On the other hand, any person who inherits the HD gene eventually will develop the disease, provided he or she lives long enough. A few cases of HD occur without any family history of the disorder. Most affected are neurons in the basal ganglia, deep structures within the brain that, among other functions, help coordinate movement.