Which of the following statements describing restriction endonucleases is true?: (A) 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
Answer is D. 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