MadSci Network: Molecular Biology |
Hello there, Well, quite simply, when you are working with recombinant DNA you will using be working with an engineered cloning host, such as an E. coli K-12 derivative for example. Such strains have had the restriction- modification (r-m) systems inactivated, and thus do not present a problem to unmodified recombinant DNA. There are usually r-m strains available in most genetically tractable hosts. I occassionally have cause to use hosts with a fully functionaing r-m system, but in these cases I have fortunately been able to either subclone using DNA prepared from this host, or by using an intermediate host that is restriction deficient, but modification proficient, which will "re-code" the recombinant DNA to look like native DNA. This is called passaging. This DNA can then be safely transformed into the final r-m proficient host. Hope this helps,
Jim Caryl |
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