This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Retinoblastoma gene regulates- \nSelect and explain. \nA. Gi - S phase, B. G2 - M phase, C. Go - S1 phase, D. S - G1 phase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' i.e., G1- S phaseo Phosphorylation of RB is a molecular "On-off\' switch for cell cycle.o It regulates cell cycle at G,- S phase (has been explained in details in previous explanations).', 'role': 'assistant'}]