Question

The restriction enzymes that cut the bacteriophage DNA cannot cut the bacterial chromosomal DNA.
Explain this statement.

A. The bacteria can cut the viral DNA at its specific restriction site, but they cannot cut their own DNA since bacterial chromosomal DNA has altogether a different DNA sequence than the viral DNA
B. The bacteria can cut the viral DNA at its specific restriction site but protect their own chromosomal DNA by modifying its bases and blocking the restriction enzyme
C. The bacteria can cut the viral DNA at its specific restriction site but protect their own chromosomal DNA by

Answer 1

The answer is B or C. It is to stop the restriction enzyme from degrading itself. From Answers.com:

Every restriction enzyme comes with a methylase enzyme, or more specifically, a DNA methyltransferase. The methylase enzyme methylates (adds a methyl group) to the restriction endonuclease site on the cell's own DNA, which protects the sites from the restriction enzyme so that it does not degrade its own DNA.

Part of answer C is cut off so I can't determine if it's B or C, but this piece of information should be of help.