This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nucleotides, Subject name: Biochemistry
[{'content': "A dideoxynucleotide does not contain \nSelect and explain. \nA. 2' & 3' OH group, B. 3' & 4' OH group, C. 4' & 5' OH group, D. 2' & 5' OH group", 'role': 'user'}, {'content': "Answer: A \nExplanation: Dideoxy nucleotide Lacks 3' OH group also. Stop the chain elongation when they are incorporated. DNA polymerase requires 3' OH group to begin polymerisation. Use: Sanger chain termination method of DNA sequencing. Didanosine is a dideoxynucleotide used in the therapy of HIV.", 'role': 'assistant'}]