What type of ends do restriction enzymes create when they cut straight across the double helix?

Restriction enzymes are biological tools that can cut DNA at specific sequences, and the type of cut they create significantly influences subsequent DNA manipulation techniques. When restriction enzymes cut straight through both strands of the double helix at the same position, they produce blunt ends. These ends are characterized by having no overlapping bases; instead, they are even at the cut site.

Blunt ends are particularly useful in cloning because they can be ligated with other blunt-end DNA fragments without the need for complementary overhangs. This creates a more uniform and straightforward means of joining DNA fragments, although it typically requires higher concentrations of DNA and ligase compared to sticky ends, which have overhangs and can easily anneal with similarly cut DNA.

The other choices describe types of DNA ends that do not correspond to a straight cut across the double helix. Sticky ends, for instance, result from enzymes that cut the DNA in a staggered fashion, leaving single-stranded overhangs that can easily bind to complementary sequences. Sharp and pliable ends are not standard terms used in molecular biology to describe DNA ends produced by restriction enzymes. Thus, the clear and precise nature of blunt ends aligns perfectly with the action of restriction enzymes making a straight cut across the DNA double helix