What are sticky ends in cloning?

• A. Complementary overhangs produced by restriction enzymes that allow joining with ligase.
• B. They degrade plasmids.
• C. They are the ends of RNA transcripts.
• D. They prevent ligation.

Answer: (A)

Sticky ends are short single-stranded overhangs left on DNA after a staggered cut by certain restriction enzymes. These overhangs are complementary to matching ends, so the fragments can base-pair with each other, guiding correct alignment. DNA ligase then seals the sugar-phosphate backbone to form a continuous molecule. This base-pairing makes ligation more efficient and can help control the insert’s orientation in cloning. In contrast, ends without overhangs (blunt ends) don’t have this pairing benefit, and other statements about plasmid degradation or RNA transcript ends don’t describe these cohesive ends.