- A A single mutation occurring in just one allele of any gene is largely sufficient on its own to cause cancer
- B Both alleles of a tumor suppressor gene must be inactivated for cancer to occur (first hit germline, second somatic in familial cases)
- C Tumor formation usually and mainly requires the sequential activation of exactly two separate, unrelated oncogenes in the same cell
- D Invading viral particles must physically and mechanically strike the DNA double helix exactly twice during a single infection cycle
Correct answer: B. Both alleles of a tumor suppressor gene must be inactivated for cancer to occur (first hit germline, second somatic in familial cases)
Explanation: Knudson two-hit model: cancer requires loss of both alleles of a tumor suppressor (e.g., Rb). In familial retinoblastoma, one mutation is inherited (first hit); one somatic (second hit).
Concept context
Mendel's laws, inheritance patterns, DNA structure, and molecular biology. Core of NEET biology.
Read the full Principles of Inheritance and Variation notes →