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: Anatomy
[{'content': 'Holt Aram syndrome is caused by mutation of: \nSelect and explain. \nA. TBX5, B. NKX2.5, C. Lefty, D. None of the above', 'role': 'user'}, {'content': "Answer: A \nExplanation: Mutations in the TBX5 gene result in Holt-Oram syndrome, characterized by preaxial (radial) limb abnormalities and atrial septal defects.Ref: LANGMAN'S EMBRYOLOGY 11TH ED Chapter 12.", 'role': 'assistant'}]