Are Developmental Mistakes Essential to Evolution? (opens in new tab)

(bigquestionsonline.com)

27 pointsjohnfjacobi9y ago4 comments

4 comments

4 comments · 2 top-level

astazangasta9y ago· 2 in thread

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.

pazimzadeh9y ago

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#.

astazangasta9y ago

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?

taneq9y ago

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.

j / k navigate · click thread line to collapse