Which enzyme can produce blunt ends?

Correct answer: Enzyme like SmaI

Direct answer: option A, an enzyme such as SmaI. Restriction enzymes cut DNA at specific recognition sequences. The cut pattern determines whether the DNA ends are sticky or blunt. SmaI cuts straight across the two DNA strands at its recognition site, producing blunt ends, in which no single-stranded overhang remains. Option A is therefore correct. Option B, EcoRI, commonly produces sticky ends with a characteristic overhang, so it is not a blunt-end example here. Option C, HindIII, also produces sticky ends rather than blunt ends. Option D, BamHI, produces sticky ends as well. The word “always” in the other options is especially unsuitable because the question asks for an enzyme known for blunt-end production, not merely any restriction enzyme. Blunt ends can be joined by ligase, although ligation is often less efficient than joining compatible sticky ends. Memory cue: SmaI is a standard blunt cutter; EcoRI, HindIII and BamHI are familiar sticky cutters.