Restriction enzymes: A) act at the membrane to restrict the passage of certain molecules into the cell. B) are highly specialized ribonucleases that degrade mRNA soon after its synthesis. C) are sequence-specific DNA endonucleases. D) are very specific proteases that cleave peptides at only certain sequences. E) catalyze the addition of a certain amino acid to a specific tRNA. c The biological role of restriction enzymes is to: A) aid recombinant DNA research. B) degrade foreign DNA that enters a bacterium. C) make bacteria resistant to antibiotics. D) restrict the damage to DNA by ultraviolet light. E) restrict the size of DNA in certain bacteria.