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I was thinking one of them would be a restriction enzyme, but I wasn't sure?
Hi, You're right that restriction enzymes are needed for making recombinant plasmids. They are called restriction enzymes because they restrict the growth of viruses that infect bacteria (bacteriophages) by digesting the virus DNA after it is injected into the bacteria. Strictly speaking restriction enzymes are endonucleases ie they cut in the middle of a DNA strand at specific sequences. These sequences are not present in the host DNA so the host DNA doesn't get cut up too. The sequence specificity is what makes them useful for recombinant DNA work - the ends of different fragments can be joined together because they have the same sequence. Hope this helps!
thank you - that explained it better than the book did!