- A Proto-oncogenes are genes that are understood to directly and immediately cause cancer formation upon their ordinary expression, even when expressed at largely normal, unamplified physiological levels in healthy cells
- B Proto-oncogenes are normal genes that regulate cell growth; mutations (point mutations, amplification, chromosomal translocation) convert them into oncogenes that drive uncontrolled cell proliferation
- C Proto-oncogenes are understood to serve no identifiable normal physiological function within healthy, non-cancerous tissue, existing in the genome mainly as inert, vestigial sequences left over from earlier evolution
- D Oncogenes arising from mutated proto-oncogenes are understood to usually be directly inherited from a parent, and are rarely the result of somatic mutations acquired during a person's own lifetime
Correct answer: B. Proto-oncogenes are normal genes that regulate cell growth; mutations (point mutations, amplification, chromosomal translocation) convert them into oncogenes that drive uncontrolled cell proliferation
Explanation: Proto-oncogenes: normal regulators of cell growth, differentiation, and division (growth factors, receptors, signal transducers, transcription factors). Gain-of-function mutations → oncogenes (act as accelerator stuck in 'on'). Examples: RAS mutation (30% of cancers), HER2 amplification (breast cancer), BCR-ABL translocation (chronic myeloid leukaemia). Oncogenes are dominant (one mutated allele is sufficient).
Concept context
Pathogens, infectious diseases, non-infectious diseases, drugs, cancer, and public health. High NEET importance.