試題詳解

16. Restriction enzymes are found in virtually all bacterial species, and their sequence specificities cover almost all possible short (4-6 bp) sequences. Why do you think this is the case?
(A) Restriction enzymes were put on Earth by a kindly God to make the lives of molecular biologists easier
(B) Restriction enzymes provide the means by which bacteria carry out gene cloning
(C) Restriction enzymes provide protection for the cell against invasion of foreign DNA
(D) Restriction enzymes provide a means to ensure that the cells’ DNA is properly and specifically methylated
(E) Restriction enzymes recognize as foreign any DNA that contains copies of their recognition sequence and destroy it