DNA and errors -Reply

Alan Junkins junkinsa at SMTPGW2.MUSC.EDU
Mon Feb 2 08:50:41 EST 1998


>>> "Rob Del" <Rob.Del at usa.net> 02/02/98 02:38am >>>
Does anyone know why DNA has about half as many errors
as RNA?  Why is this OK?  Just curious.

------------------------

I would think that the main reason RNA has more errors than
DNA is that RNA polymerases lack the "proofreading"
abilities that most DNA polymerases have.  These allow DNA
polymerase to back up and remove bases that are
mismatched.  There is also an excision repair mechanism
that finds and remove errors in DNA like mismatches and
thymine dimers.  This is important in DNA because DNA is
the permanent storage facility for genetic information.  RNA
molecules are degraded fairly quickly.  If there's a mistake in
the DNA then it's going to be replicated over and over ad
infinitum.  A mistake in an RNA molecule is not that big of a
deal because it's only going to affect that one single
molecule.  The worst that would be expected is an RNA
molecule that just doesn't work.  But that's okay because
there are lots of other RNA molecules to take up the slack. 
Actually, I'm kind of surprised by your statement that RNA
has twice as many errors as DNA.  I would think RNA would
have even more errors than that.

Alan Junkins




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