dam-/dcm- bugs and mutations??

Chris Boyd chrisb at hgu.mrc.ac.uk
Fri Feb 21 05:29:17 EST 1997


Dr. Duncan Clark (duncan at genesys.demon.co.uk) wrote:
: In article <5e2s4i$20c8 at piglet.cc.uic.edu>, Victor Levenson
: <levenson at uic.edu> writes
: >I need to cut my construct with BclI and - therefore- have to put it
: >through dam/dcm- strain (DM1, in my case). These bugs do not repair
: >mismatches that occur during DNA replication (I assume that the
: >enzymology of plasmid replication is the same as for the genomic DNA
: >;-)).


: If E.coli B which is naturally dcm - was mismatch repair minus it would
: mutate horribly. I'm think you may be mixing up mutS, mutL mutations
: with dam and dcm. I've never seen a report that says dam dcm- strains
: are mismatch repair minus so I wouldn't worry. 

On the other hand, dam- mutants are defective in strand discrimination
during mismatch repair and are therefore slightly more mutagenic than
wild-type.  Not enough to worry about in practice, though, I think.

See for example:

  author =       "M. G. Marinus and N. R. Morris",
  title =        "{Pleiotropic effects of a DNA adenine methylation
                 mutation ({\it dam\/}-3) in {\it E.~coli} K-12}",
  journal =      "Mut. Res.",
  volume =       "28", 
  pages =        "15--26",
  year =         "1975",

  author =       "M. G. Marinus and A. Poteete and J. A. Arraj",
  title =        "{Correlation of DNA adenine methylase activity with
                 spontaneous mutability in {\it Escherichia coli}
                 K-12}",
  journal =      "Gene",
  volume =       "28",
  pages =        "123--125",
  year =         "1984",

: For Bcl I, you just need dam-. Try JM110 or I think Stratagene have an
: endA derivative. 

Yes.  But you can get GM2163 (dam- dcm-) *free* with an order from NEB.
Expect to get much reduced transformation efficiency and plasmid yield
from a dam- strain.

Best wishes,
--
Chris Boyd                       | from, | MRC Human Genetics Unit
chrisb at hgu.mrc.ac.uk             |  not  |  Western General Hospital
http://www.hgu.mrc.ac.uk/~chrisb |   for |   Edinburgh EH4 2XU, SCOTLAND



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