Genetic Engineering and Recombinant DNA Technology

ID #1463

I had a simple question regarding the insertion of DNA into the vector. I know that genomic DNA is inserted into the vector, but I am a bit confused. I thought that the restriction enzymes were not allowed to cut the host DNA. Isn't it the host DNA that is inserted to the vector though?

When thinking about bacterial restriction enzymes, remember that the enzymes of one organism are not looking for the same sequences as the enzyme of another organism. So if you are trying to study the DNA of species X, and prepare a genomic library using EcoRI, the restriction sequence that EcoRI is looking for wouldn't be "protected" in species X. Unless, however, species X was E. coli. In this particular case, what we would use is a special lab strain of that organism that fails to methylate its DNA in those locations, allowing us to digest its DNA without having to worry about methyl groups being passed by.

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