This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thalassemia, Subject name: Medicine
[{'content': 'Cause of alpha thalasemia - \nSelect and explain. \nA. Deletion of alpha genes, B. Deletion of beta genes, C. Excess of alpha genes, D. Single amino acid substitution in alpha chain', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Deletion of alpha genes a thalassemiasAlpha thalassemias are hemoglobin disorders in which the a chain of the hemoglobin is not/partly synthesized. a chains are required for all types of hemoglobin synthesis of all types of hemoglobin i.e.HbA (a2 b2)HbF (a2 g2)* HbA2 (a2d2)", 'role': 'assistant'}]