Q.Write three differences between each of the following:

Nucleases (Exonucleases and Endonucleases)

A strand of DNA or RNA is a chain of nucleotides held together by phosphodiester bonds — the "backbone" links between one sugar and the next. Nucleases are the enzymes whose job is to cut these bonds. Think of them as molecular scissors for nucleic acids. But not all scissors cut in the same place, and that difference is the whole point.

The two ways to cut

• Exonucleases remove nucleotides one at a time from the ends of a DNA or RNA molecule. They chew inward from a free 5′ or 3′ terminus, shortening the strand progressively. Because they need a free end, they cannot attack the middle of a closed circular molecule.
• Endonucleases cut internally, breaking a phosphodiester bond somewhere within the strand rather than at a tip. This produces two shorter pieces from one longer molecule.

The prefixes make it easy: exo- means "outside/end", endo- means "inside".

Why this matters — restriction enzymes …