A 5-year-old female is kept indoors during the day on the advice of the family physician, who has determined that there is a family history of skin cancers. Which of the following mechanisms explains why the child is at risk with sun exposure:
A Balanced chromosomal translocation
B Rb-1 mutation
C c-erb B2 amplification
D Defective DNA repair
E k-ras activation
(D) CORRECT. The child has the rare autosomal recessive condition known as xeroderma pigmentosa in which faulty DNA repair genes are unable to repair the damage of ultraviolet light in cross-linking pyrimidine residues.
M.D., PGY-3 Internal Medicine