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Plasmid stability

Edward Braun ebraun at mail.unm.edu
Thu Jul 6 15:06:20 EST 1995

In article <3terl3$hqu at cisunix1.dfci.harvard.edu>
york at mbcrr.dfci.harvard.edu (Ian A. York) writes:

> This may be too broad a question, but what the heck.  How stably are 
> plasmids maintained in S cervisiae?  That is, if you stop selective 
> pressure, and assuming that the plasmid isn't expressing something toxic, 
> what kind of half-life will it show?  Will most of the plasmid be lost 
> after 6 hours in culture?  24 hours?  A week?  Or is it unpredicatable, 
> or does it depend on other conditions?  I'm specifically thinking of 2 
> micron plasmids, but any information would be helpful.
> Ian
> -- 
> Ian York   (york at mbcrr.harvard.edu)
> Dana-Farber Cancer Institute, 44 Binney St., Boston MA 02115
> Phone (617)-632-3921     Fax  (617)-632-2627

The chapter on "Cloning Genes by Complementation in Yeast" in Meth.
Enzymol. (by Mark Rose and James Broach, pp. 195-230, vol. 194)
contains info. on the stability of YEp and YCp plasmids (overnight
growth under non-selective conditions will yield 90-99% YCp containing
cells and 80-95% YEp containing cells).  This info. is on pages 199 and
206.  We use the vectors of Gietz and Sugino quite a bit, and info. on
thier stability (as well as a ref. to other plasmids) is given in the
article describing these plasmids (Gene 74:527 [1988]).  In my
experience, growing cultures to saturation under non-selective
conditions can result in quite a bit of plasmid loss - e.g. growth of a
diploid with a LEU2 marked CEN plasmid to saturation results in less
than half of the colonies that grow on YPD being Leu+.  I haven't
looked at YEp plasmids in the same way.

Also, larger CEN plasmids are more stable - this is stated in the
Gietz&Sugino ref. (and elsewhere, but I can't remember off the top of
my head) and I observed it in the expts. I described above.

Hope this was of help...sorry I didn't have more info directly relevent
to YEp's!

Edward Braun
Univ. of New Mexico
Dept. of Biology
(ebraun at mail.unm.edu)

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