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: Pathology
[{'content': 'Retinoblastoma gene is located on a chromosome - \nSelect and explain. \nA. 13, B. 6, C. 9, D. 21', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Location of retinoblastoma (RB) gene is 13 q 14\nDeletion of a small number of tightly clustered genes result in a number of genetic disorders termed as microdeletion syndromes', 'role': 'assistant'}]