Posted: Apr 16, 2019 11:21 pm
by Wortfish
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. 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.

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.

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!

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.

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

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