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: Radiology
[{'content': 'If the radiation exposure occurs before DNA synthesis, the damage manifests: \nSelect and explain. \nA. One arm of chromosome, B. Both the arms of chromosome, C. Shorter arm of chromosome, D. None of the arm of chromosome is affected', 'role': 'user'}, {'content': 'Answer: B \nExplanation: If radiation exposure occurs after DNA synthesis (i.e., in G2 or mid and late S), only one arm of the affected chromosome is broken.\nIf radiation induced break occurs before DNA has replicated (i.e., in G1 or early S), the damage manifests in both arms (Chromosome aberration) at the next mitosis.', 'role': 'assistant'}]