Question

Cohesive ends of DNA are produced by restriction endonucleases when

• A. They cleave both strands of DNA so as to never leave no unpaired bases on either end.
• B. They make staggered cuts on the two DNA strands leaving some nucleotides of one strand unpaired at each end.
• C. They cut the methylated strand of the host DNA by error.
• D. Enzymatic digestion of the strand follows from one end after action of the endonuclease.

Answer 1

The correct option is B They make staggered cuts on the two DNA strands leaving some nucleotides of one strand unpaired at each end.

Nucleotide overhangs are called cohesive ends or sticky ends. They are very often created by restriction endonucleases when they cut DNA. In many cases, they cut the two DNA strands four base pairs from each other, creating a four-base 5' overhang in one molecule and a complementary 5' overhang in the other.