Answer: Both alleles of a tumor suppressor gene must be inactivated for cancer to occur (first hit germline, second somatic in familial cases).
- 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).
Punnett square for a monohybrid cross between two heterozygous (Tt) parents, showing the 3:1 phenotypic ratio predicted by Mendel's Law of Segregation.
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 →