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': 'Thalassemia occurs due to which mutations -a)  Missenseb)  Splicingc)  Transitiond)  Frame-shifte) Truncation \nSelect and explain. \nA. c, B. d, C. ab, D. bd', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Thalassemia syndrome\n\nAdult hemoglobin is a tetramer, composed of two α globin chains and two β globin chains.\nThalassemia is an inherited autosomal recessive disorder.\nIn thalassemia, the genetic defect results in reduced β synthesis of one of the globin chains of hemoglobin.\nβ-Thalassemia is caused by deficient synthesis of β-chain with normal β-chain synthesis.\nα-thalassemia is caused by deficient synthesis of α-chain with normal β-chain synthesis.\nMolecular defect in pathogensis of thalassemia.\n\nA. β-Thalassemia\n\nMost common type of genetic abnormality in β-thalassemia is point mutation i.e., nonsense.\nSome may also occur due to deletion or insertion i.e., frame shift mutations.\nDefect may occur at different steps of β-chain synthesis.\n\n(i) Splicing mutations\n\nMutations leading to aberrant splicing are the most common cause of β-thalassemia.\n\n(ii) Chain terminator mutations\n\nThis cause premature termination of mRNA translation.\n\n(iii) Promoter region mutations\n\nThis results in transcription defect.\n\nB. α-Thalassemia\n\nThe most common cause of reduced a-chain synthesis is deletion of α-globin genes.\nRarely nonsense mutation may also cause α-thalassemia.', 'role': 'assistant'}]