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
[{'content': '7-Methyl guanosine cap is present in: \nSelect and explain. \nA. mRNA, B. tRNA, C. rRNA, D. DNA', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ref: Harper\'s Illustrated Biochemistry. 28th ed, ch. 36,pp-349Explanation:"The 52 cap is found on the 52 end of an mRNA molecule and consists of a guanine nucleotide connected to the mRNA via an unusual 52 to 52 triphosphate linkage. This guanosine is methylated on the 7position directly after capping in vivo by a methyl transferase. It is referred to as a 7-methylgu- anylate cap, abbreviated m G."Capping - 5\' endAddition of modified nucleotide7-methylguanosine to 5\' endGuanvl transferase & methyl transferase.FunctionsmRNA recognitionPromotion of 52 proximal intron excision.Prevention of degradation by exonucleases.Regulation of Nuclear Transport/ExportPromotion of translation & Stability', 'role': 'assistant'}]