What ends are produced by staggered cuts that enable joining of DNA fragments?

• A. Sticky ends
• B. Blunt ends
• C. Double-stranded ends
• D. Circular ends

Answer: (A)

Staggered cuts by restriction enzymes create ends with short single-stranded overhangs. These overhangs are sticky because they can pair with complementary overhangs on another DNA fragment, guiding correct base-pairing before the backbone is sealed by ligase. This cohesive pairing makes joining fragments efficient and directional, which is why these ends are called sticky ends.

Blunt ends, in contrast, have no overhangs and must be ligated without the guiding base-pairing, making the process less efficient and less specific. The term double-stranded ends isn’t the standard way to describe the outcome of staggered cuts, and circular ends refer to circular DNA rather than the overhangs created by staggered cuts.