Huntington disease can strike at an earlier age and bring about a more rapid degeneration and death in successive generations within a family.This phenomenon can be explained by which mechanism?

A)Presence of a transposable element in the gene
B)Chronic exposure to mutagens in the environment
C)Expansion of a trinucleotide repeat in the coding sequence of the gene
D)Presence of an extra chromosome in the germ line
E)Absence of a gene product that is involved in DNA repair