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Plasmid stability

John BRATTY bratty at BCH.UMontreal.CA
Fri Jul 7 17:04:55 EST 1995


york at mbcrr.dfci.harvard.edu (Ian A. York) wrote:

   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

Gietz and Sugino (Gene 74, 527-34 1988) determined the mitotic
stability of a series of shuttle vectors they constructed, including
both centromeric and 2micron based plasmids.

With the CEN-ARS plasmids, they found that 74-91 percent of viable
cells still carried the plasmid after 24 hours of growth under
selective conditions, while 28-45 percent still contained plasmid
after a further ten generations of growth in non-selective medium
(YPAD).

The 2micron plasmids were more stable, being found in 87-97 percent of
cells after the selective culture and 72-87 percent after the
non-selective growth period in the same strain background.

They also cite other work that gave essentially similar results. In
very approximate terms and subject to the usual caveats, then, it
seems you can expect about 1 percent loss per generation with 2micron
plasmids, and about 5 percent for ARS-CEN plasmids when you grow them
without selection.

You can take it from there for your 6 hr, 24 hr, 1 week cultures.

Cheers, 

John

--
=========================================================
John Bratty			bratty at bch.umontreal.ca
Departement de biochimie	
Universite de Montreal		(514) 343-6111, ext. 5165
Montreal, Canada		(514) 343-2210  (fax)
H3C 3J7
=========================================================



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