Answer: Proto-oncogenes are normal genes that regulate cell growth; mutations (point mutations, amplification, chromosomal translocation) convert them into oncogenes that drive uncontrolled cell proliferation.
- 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).
The Plasmodium parasite needs both hosts: the female Anopheles mosquito injects sporozoites while biting (infecting the human liver and RBCs, causing the malaria fever cycle), then picks up gametocytes from an infected person's blood, completing the parasite's sexual stage inside the mosquito.
Concept context
Pathogens, infectious diseases, non-infectious diseases, drugs, cancer, and public health. High NEET importance.