Huntington's chorea is

a. usually first expressed when the affected person is between 30 and 40 years of age.
b. caused by homozygous recessive lethal genes.
c. caused by the inability to produce the proper balance of amino acids.
d. associated with mania as well as with violent and aggressive behaviors.
e. associated with excessive genetic material in chromosome 21.

Answer: a. usually first expressed when the affected person is between 30 and 40 years of age.