MadSci Network: Molecular Biology
Query:

Re: why recombinant DNA is not attacked by host(bacteria) endonucleases

Date: Tue Jun 21 05:49:31 2005
Posted By: Dr. Jim Caryl, Research Scientist
Area of science: Molecular Biology
ID: 1118134351.Mb
Message:

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
MAD Scientist


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