Duchenne muscular dystrophy is caused by a sex-linked recessive allele. Its victims are almost invariably boys, who usually die before the age of 20. Why is this disorder almost never seen in girls?

Correct Answer: D

Rationale: DMD is X-linked recessive. Females (XX) need two mutant alleles to be affected (rare), while males (XY) need only one, explaining the male predominance.

Correct Answer: B

Rationale: Telomerase is inactive in most somatic cells, leading to telomere shortening with each division, unlike cancer cells where it’s often active.

Correct Answer: D

Rationale: The BCR-ABL fusion protein from t(9;22) is a tyrosine kinase that deregulates myeloid cell proliferation.

Correct Answer: A

Rationale: APC (adenomatous polyposis coli) is the primary gatekeeper gene in familial adenomatous polyposis, initiating polyp formation when mutated.

Correct Answer: B

Rationale: Cruciferous vegetables (e.g., broccoli) contain compounds (e.g., sulforaphane) linked to reduced cancer risk.