Autoclaves destroy DNA???

Matt Kaeberlein n9410619 at ROWLF.CC.WWU.EDU
Tue Aug 6 19:04:44 EST 1996



On 6 Aug 1996, Barn wrote:

> 
> 
> > 
> >      I have heard diametrically opposed statements about the
> effectiveness of
> > standard steam autoclaves in terms of destroying DNA (on microtubes,
> forceps,
> > pestles, etc.) such that PCR will not amplify any DNA that may have been
> on
> > the autoclaved items.  One group says that 15-20 min in the autoclave at
> 121C
> YES, autoclaving will destroy DNA.  To be sure, autoclave small batches for
> 30-45 minutes.  121C is beyond the melting point of any DNA.
> 
> 
> 
While it is true that 121C is above the melting point of dsDNA, you are 
forgetting the fact that melted DNA will spontaneously reanneal.  It 
seems likely that if in fact autoclaving DNA "destroys" it, this is due to a 
covalent chemical alteration such as loss of a base or hydrolysis of the 
sugar-phosphate backbone, and is not due to the breaking of noncovalent 
bonds as occurs during melting.  However, you have to be careful what you 
mean by "destroying DNA".  Do you mean that a PCR amplification of the 
autoclaved DNA will no longer yield high copy numbers of the original DNA 
molecule (the sequence integrity will be compromised), or do you mean 
that you will get no PCR amplification whatsoever?   



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