試題詳解

74. Restriction-modification systems:
(A) exist in all organisms as a protection against foreign DNA invasion.
(B) include a site-specific exonuclease to degrade foreign DNA.
(C) modify DNA by acetylation.
(D) include a DNA methylase and an endonuclease.
(E) include three types of endonuclease all of which cleave within a specific DNA target sequence.