Which of the following is true regarding restriction enzymes?
1)Methylation protects an organism's DNA from cutting by restriction enzymes
2)Restriction enzymes are exonucleases
3)Restriction enzymes can make staggered or blunt cuts
A) 1
B) 2
C) 3
D) 1 and 2
E) 1 and 3

Question

Quizplus · Accepted Answer

Methylation of DNA protects it from restriction enzymes by adding methyl groups to specific bases. This modification affects the recognition and cutting sites for restriction enzymes. Therefore, methylation prevents restriction enzymes from cleaving at specific sites. 
Restriction enzymes can make staggered (sticky) or blunt cuts in DNA. They are endonucleases, meaning that they cleave the phosphodiester bonds within the DNA chain, rather than at the ends of the molecule. Therefore, statement 2 is incorrect, which leaves us with choices (C), (E), and (D). Since choice (E) includes the correct and only answers, it is the best choice.

Which of the Following Is True Regarding Restriction Enzymes