Newly Replicated, and Consequently ________, DNA Sequences are Invisible to a Restriction

Question

Newly replicated, and consequently ________, DNA sequences are invisible to a restriction enzyme.
A) mutated
B) restricted
C) modified
D) hemimethylated
E) single-stranded

Accepted Answer

Restriction enzymes recognize and cleave DNA at specific recognition sites; these sites are often palindromic and can only be recognized if the DNA is fully hemimethylated (i.e., it has methyl groups on one strand but not the other). Newly replicated DNA is hemimethylated, so it is temporarily invisible to restriction enzymes until the DNA methyltransferase fully methylates both strands.