Question

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.

Answer 1

Answer: C

Explanation: Expansion of trinucleotide repeat can cause defect encoded by a gene, change regulation of gene expression and chromosome instability. So the larger the expansion the faster the onset of the disease and the more likely it becomes.