Posted: Apr 16, 2019 10:49 pm
by Rumraket
Wortfish wrote:
Rumraket wrote:
Wortfish wrote:
Rumraket wrote:
I would agree that it's a badly worded sentence. What they mean is that additional duplications of the tripeptide repeat also happened after the proto-ORF had ackquired transcriptional regulation. That's why the dark blue part in the figure become significantly longer in the last step F, as they write in the figure legend: "(F) Intragenic (Thr-Ala-Ala)n cds amplification, fulfilling the antifreeze function under natural selection."

Actually, there were 3 duplication events claimed by the authors. Look again at the figure.

Yes, and the one under selection is the last one. Obviously.

The duplication event I am referring to is step C which precedes Step D (the gain of the promoter):

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. As the number of AFGP tripeptide-coding repeats increased, the antifreeze function would become augmented.

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.

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.

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).

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: