restriction enzymes - (Sep/28/2006 )

does any one know what are the role of restriction enzymes (used in the lab) in a living cell? what do they do? ....

thanks

They are used to kill/eliminate invating foreign DNAs.

what about if in bacteria....,phags are also metylated, would the enzyme recognize them?

if phage dna is methylated i think maybe thats adaptation on part of virus to evade cell resistance mechanism ,,, there might be some other way that cells fight then , like at the protein level or RNA silencing level

methlylation patterns are also strain specific, so a phage adapated to one strain will not easily attack another strain. Which in a normal mixed population gives immunity to the population as a whole, as the phage can not easily hop from one individual to another (who may be a different strain)