Question

Cohesive ends of DNA are produced by restriction endonuclease when

• A. they cleave both strands of DNA so as to leave no unpaired bases on either end
• B. they make staggered cuts on the two DNA strands leaving two to four nucleotides of one strand unpaired
• C. they cut the methylated strand of host DNA by error
• D. enzymatic digestion of DNA strand leave unpaired bases on both ends of the two strands

Answer 1

The correct option is D enzymatic digestion of DNA strand leave unpaired bases on both ends of the two strands

Restriction enzymes are DNA cutting enzymes. Restriction endonucleases cleave DNA duplexes at specific points in such a way that they come to possess short single-stranded free ends. As a result, the DNA fragments produced by cleavage with these enzymes have a short single-stranded overhang at each end of the two strands. These kinds of ends are called sticky or cohesive ends because base pairing between them can stick the DNA molecule back together again. Hence, cohesive ends of DNA are produced by restriction endonuclease when enzymatic digestion of DNA strands leave unpaired bases on both ends of the two strands.