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
Cause of alpha thalasemia - 
Select and explain. 
A. Deletion of alpha genes, B. Deletion of beta genes, C. Excess of alpha genes, D. Single amino acid substitution in alpha chain
A: Deletion of alpha genes
Answer: A: Deletion of alpha genes 
Explanation: 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)