This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Transcription, Subject name: Biochemistry
Initiation and Termination of a sequence of intron : 
Select and explain. 
A. GU,AG, B. AG,GU, C. GA,GU, D. UG,AG
A: GU,AG
Answer: A: GU,AG 
Explanation: The sequence of the intron is unique. It always stas with GU and ends with AG Any mutation in these sequences will lead to defective splicing. e.g. b thalassemia.