Which option gives the correct summary of a restriction enzyme?

Correct answer: Enzyme that cuts a specific DNA sequence

The defining property of a restriction enzyme is sequence-specific cleavage of DNA. Each enzyme recognizes a particular short nucleotide sequence, often a palindromic sequence, and cuts the phosphodiester backbone at a characteristic position. This precise action makes restriction enzymes useful for isolating genes, opening cloning vectors, and constructing recombinant DNA molecules. Option A gives this essential summary. A pigment that colours protein, a mineral that freezes water, and a hormone that stores fat do not describe the nature or function of restriction enzymes. Thus A is the only scientifically correct option.