This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
[{'content': 'Which of the following statements describing restriction endonucleases is true? \nSelect and explain. \nA. They always yield overhanging single-stranded ends, B. They recognize methylated DNA sequences, C. They recognize triplet repeats, D. They cleave both strands in duplex DNA', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Inside a prokaryote, the restriction enzymes selectively cut up foreign DNA in a process called restriction; meanwhile, host DNA is protected by a modification enzyme (a methyltransferase) that modifies the prokaryotic DNA and blocks cleavage. Together, these two processes form the restriction modification system A palindromic recognition site reads the same on the reverse strand as it does on the forward strand when both are read in the same orientation Restriction enzymes recognize a specific sequence of nucleotides and produce a double-stranded cut in the DNA', 'role': 'assistant'}]