Posted: Apr 17, 2019 12:01 am
by Rumraket
Wortfish wrote:
Rumraket wrote:
No, that's not the one. The part you quote is speaking of the last step F. That's the duplications under selective pressure. Obviously.

No, it isn't.

Yes it is.

From the figure legend:

(C) A 9-nt in the midst of the four 27-nt duplicates became the three codons for one AFGP Thr-Ala-Ala unit and underwent microsatellitelike duplication forming a proto-ORF.
(D) A proximal upstream regulatory region acquired through a putative translocation event.

That doesn't contradict what I said.

They explain in the main text that:
We hypothesize that, upon the onset of selective pressure from cold polar marine conditions, duplications of a 9-nt ancestral element in the midst of the four GCA-rich duplicates occurred.

This is clearly stage C, and not stage F, that they are referring to.

No, it clearly isn't. The segments being duplicated in stage C and F are the same, the Threonine-Alanine-Alanine tripeptide encoded by a 9-nucleotide repeat.

The other can't be under selective pressure, because at that time there was presumably no expression of the gene, and even if there were, before the association with a signal peptide the protein is unlikely to have found itself in the bloodstream of the fish.

That is precisely my point!

Then all the more reason not to think the authors are somehow stupid and would seriously postulate that selection somehow made duplications happen in a locus not being expressed.

There has to be some sort of limit to how stupid we should allow ourselves to think the authors are. You are familiar with the concepts of strawmanning and steelmanning? Rather than giving their words a deliberately hostile interpretation, try to be at least somewhat charitable and assume they can think.

So again, the authors merely expressed themselves badly(and you seem to have got the mistaken impression that they're saying the first duplications were under selection).

Yes. They are claiming that the initial microsatellite repeats of the 3 codon element that make up most of the protein occurred because of selective pressure before the acquisition of the promoter and the frameshift creating a read through ORF with the signal peptide.

No, there is absolutely zero fucking reason to think they are claiming that, and only a braindead creationist tool with a pseudoscientific political agenda would deliberately ascribe to them this fatuous insinuation.

They are not actually claiming the gene duplications that happened prior to the locus acquiring a promoter, were evolving under selection before it was expressed. They clearly and obviously only meant to say that the repeat expansions that happened in the last step F were the ones that were happening under selection. You are making a big deal out of nothing. Get over it already. :roll:

Even if you are right - and they did not imply selection was involved with the first two bouts of duplication - the formation of the ORF would have been made possible only through completely chance mutations

What's a "completely chance" mutation and how would those be different from mutations happening even if a particular selection pressure is in operation? Natural selection doesn't make particular mutations happen. It instead acts to bias their rate of increase or decrease in frequency in the population when and if they occur, should those mutations have an effect on fitness.

- but occuring in a very nice order - along with random drift. That is wishful thinking to say the very least.

No, it's a completely straightforward explanation of the pattern observed from comparative genetics of the sample of fish taxons being stuided. These are the types of patterns expected to exist if a protein coding gene evolved from non-coding DNA.

They also offer no explanation for how parts of the sequence were spliced out as introns.

What are you even talking about here?