
Are Developmental Mistakes Essential to Evolution? - johnfjacobi
https://www.bigquestionsonline.com/2016/07/28/are-developmental-mistakes-essential-evolution/
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astazangasta
This is pure gibberish. Mutations don't have any effect other than their
consequence in expressed form - a mutation that alters protein folding is just
a mutation like any other. And biologists generally hate the concept of
"evolvability", which usually (as in this case) has no mechanistic basis.

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pazimzadeh
The author is talking about the effects of errors in transcription (G1 phase),
not replication (S phase).

Cells generally function in this way: DNA -> RNA -> protein

Replication is: DNA -> DNA

If a #mutation happens in replication (DNA -> DNA#) then the next generation
of cells will have (DNA# -> RNA# -> protein#)

A mistake in transcription (DNA -> RNA# -> protein#) wouldn't affect the
germline.

The question now is: does it benefit cells to have a decent rate of errors in
transcription so that if perchance a real mutation happens, the system has
already been tested for possible adverse effects? In effect, the cell is
resilient to possible new mutations because it has already seen them in a
subset of protein# that came from RNA#.

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astazangasta
I understand the proposition, it just doesn't make any sense. Let's say there
is an error in transcription, and you make a faulty transcript that gets
deleted by NMD. So... what? What consequence does this have for the cell? It
just means a transcript was lost; the cell has no memory of this event, once
the transcript is recycled and its protein byproducts digested. This is why
transcription can be less reliable than replication, because transcripts are
disposable and mutations in them have very little consequence.

If you mean that it is better to have a fault-tolerant system where potential
errors are masked, this advantage exists in _spite_ of a decent rate of error
in transcription, not because of it. That is because errors in the germline
are fundamentally different from errors in transcription - they are
constitutive, present in every cell, and the cell cannot escape them merely by
discarding the transcript.

Now, presumably mutations that would be horrific germline mutations (a
nonsense POLE mutation, let's say) happen all the time in some transcripts in
some cells. So what? In what way has the "system" (the organism) been tested
for the effect of this mutation at the germline by one shitty transcript in
one cell, which was immediately discarded in favor of another, working
transcript?

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taneq
The word 'mistake' implies intention. There's no such thing as a mistake in
evolution, any more than there's such a thing as a 'failed' scientific
experiment.

