2x vector plasmid

Russell A. Maurer ram3 at po.CWRU.Edu
Fri Jul 23 16:27:11 EST 1993

In a previous article, GIETZ at bldghsc.lan1.umanitoba.ca () says:

>I know for a fact that I have run across (years ago) a copy of pBR322 
>that is a dimer!
>A direct repeat not an inverted repeat.  It seemed stable and
>cannot be identified as such until you run supercoiled DNA on agarose
>to compare to a standard.  I have run across many other things in my cloning
>adventures that look like direct repeats and seem to be stable.  I have 
>a number of plasmids with large direct repeats that seem stable in coli.  I 
>recover inverted repeats of any type!  This is my $0.02 worth.
>Dan Gietz
>R.Daniel Gietz Ph.D.
>Assistant Professor
>Department of Human Genetics
>University of Manitoba
>770 Bannatyne Ave, Rm 250
>Winnipeg, Manitoba, Canada
>R3E 0W3
>Tel.: (204)789-3458
>Fax.: (204)786-8712
>"Trying to do the Manitoba Thing"
>REPLY FROM: Gietz, Dr. Dan
>Return-Path: <BIOSCI-REQUEST at net.bio.net>
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>Date: Tue, 1 Jan 80 17:21:11 PST  
>From: "Johan de Boer" <jdboer at sol.UVic.CA>
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>To: methods-and-reagents at net.bio.net
>Subject: Re: 2x vector plasmid
>I was also under the impression that a vector dimer would be unstable once
>it starts replicating. That's why my confusion, and that's why my original
>question. If someone really knows that such dimers can indeed exist I would
>like to know (reference?).
Such dimers and higher multimers have been known for a long time.  For a
recent (and provocative) reference see Summers et al., "Multicopy plasmid
instability: the dimer catastrophe hypothesis" in Molecular Microbiol.
8:1031-1038 (1993).

Russ Maurer

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