RE: [HAPS-L] Mutations

[Ken Saladin <ksaladin@xxxxxxxxxx>]

> We only see
> noncoding DNA in living organisms, so that skews our view of how many
> "harmless" mutations occur.  We never get to see the
> mutations that result in a failure to produce an observable
> offspring.
>  
> --Bill
> William Caldecutt, Ph.D.
> Polk Community College


That still doesn't answer my point. 

My point is that if 98% of the DNA is noncoding, and IF (an arguable
point) mutations are random with respect to whether they occur in coding
or noncoding regions of the DNA molecule, and IF (also an arguable point)
mutations in noncoding DNA do not harm organismal function, then most
mutations can be expected to be harmless. The fact that lethal mutations
are not represented among the living observable population is quite
irrelevant to that prediction.

That second "if" may be the most salient, since damage to
noncoding DNA perhaps can affect spacing or other nontranscriptional
functions that might affect organismal function. But even if the
frequency of harmless mutations is offset by that, it still seems
plausible that mutations may be harmless much more often than the
conventional wisdom says -- indeed perhaps in a substantial majority of
cases. Even if some mutations of noncoding DNA did affect spacing or
other structural functions, it would take an awful lot of mutations of
that sort to offset that 98% figure.

Ken

At 08:40 AM 2/19/2007, you wrote:


        You're only considering mutations that happen in gametes and result in surviving offspring.  What about all of the mutations that happen in gametes and cause death or malfunction of the gamete, or inviable offspring.  What about all of the mutations in somatic cells?
        
        --Bill
        
        William Caldecutt, Ph.D.


I don't see why you think I'm considering only survivable and transmissible mutations. Can you clarify? I think my question includes both somatic and germline mutations, as well as the whole spectrum of lethal, sublethal, and harmless mutations.

Ken

        The conventional wisdom is that most mutations are deleterious. But if 98%
        of the DNA is noncoding (and with certain other assumptions that seem of
        only peripheral relevance), wouldn't it be more accurate to say that a
         considerable majority of mutations are harmless?
        
        Just a bit of food for thought.
        
        Ken