How do restriction enzymes protect bacteria from viruses?

Answer 1

What was previously said before but it should be noted that the enzymes might not be able to detect the DNA strands from the virus before it incorporates into the actual bacteria's DNA.

Answer 2

In addition to the previous two responses,
which are good. I'll add:

But then why doesn't these restriction enzymes attack the host's DNA.
Answer: The host will methylate their specific sites thus protecting it from the specific R.E.s

There are also non-specific nucleases (DNAses and RNAses) and proteinases that can try to degrade an invader before it take hold.
Some still get through tho.
It's an evolutionary cat and mouse game.

Answer 3

hlm124. You answer reads as though you selected words at random from the index of a biology text. I have no idea what biology "A" is but if it is beyond what we in the states consider to be freshman biology (9th grade) then you should be ashamed. Not of your ignorance, but of your posturing. In science there is NOTHING worse than a loud voice who lacks the integrity to keep quiet when he/she dosn't know. Shouting the wrong answer influences people more than the most carefully whispered truth. This is a defect in our species, but one that can be avoided. Want to be a biologist? Become a Man/Woman first by taking responsibility for your words. Lamic.. lovely. I found the DAM methylase story so intriguing as a young student I did my Ph.D. in DNA repair. I was sad to see that someone else had beat me to the answer, but was glad that SOMEONE set the record straight.

Answer 4

They cut up any foreign DNA that enters the cell, thereby preventing viral proteins from being synthesised.