[Campbell Biology P.445] Which of the following statements accurately compares the normal fu... | Practice Question

Which of the following statements accurately compares the normal functions of proteins encoded by proto-oncogenes and tumor-suppressor genes?

  • A: Proto-oncogene products stimulate cell division, while tumor-suppressor gene products inhibit cell division.
  • B: Proto-oncogene products inhibit cell division, while tumor-suppressor gene products stimulate cell division.
  • C: Both proto-oncogene and tumor-suppressor gene products promote cell differentiation.
  • D: Both proto-oncogene and tumor-suppressor gene products cause cancer when mutated.

Explanation

Proto-oncogenes normally encode proteins that stimulate cell division, acting like the 'gas pedal' for the cell cycle. Mutations that make them overly active convert them to oncogenes, leading to excessive cell division. Tumor-suppressor genes, on the other hand, encode proteins that inhibit abnormal cell division, acting like the 'brake pedal.' Mutations that reduce their activity lead to uncontrolled cell division and cancer.