Huntington disease (HD) is a well-studied, autosomal dominant disorder that affects the nervous system. Symptoms usually appear after age 40, and victims usually die within 10 to 15 years after onset of the disease. It appears that at least in some cases of HD, "stutter" mutations occur. Such mutations are characterized by ________.
A) uncontrolled verbal capacity of patients
B) extra trinucleotide repeats within the HD gene
C) RNA polymerase imperfections leading to altered DNAs
D) repeated DNA polymerases generating too many coding symbols
E) links between monoamine oxidase A (MAOA) and hexokinase