[Campbell Biology P.439] Which of the following statements best explains why a cancer-causin... | Practice Question

Which of the following statements best explains why a cancer-causing mutation in a tumor-suppressor gene like p53 is generally considered to be recessive at the cellular level?

  • A: The mutated gene produces a hyperactive protein that actively promotes cell division.
  • B: The presence of just one normal allele is usually sufficient to produce enough functional protein to prevent uncontrolled cell growth.
  • C: The mutation leads to the complete absence of the protein, which is a dominant effect.
  • D: It enhances the inhibitory function of the cell cycle, which is a dominant trait.

Explanation

Tumor-suppressor genes, like p53, normally function to prevent uncontrolled cell growth. For a cancer-causing mutation to manifest its effect, both alleles typically need to be inactivated because the presence of even one functional normal allele can often produce enough protein to maintain the tumor-suppressing function. Therefore, such mutations are generally considered recessive at the cellular level.