The evolution of “irreducibly complex” antifreeze proteins in a polar fish...



(Dave Carlson) #2

Very cool! The paper is here.


More challenging yet is identifying the selective pressures and molecular mechanisms that created these putative new genes, and the adaptive functionsand species fitness they may confer.

The well-known mechanism of evolution by gene duplication from a preexisting ancestor as diverse as C-type lectin and sialicacid synthase followed by sequence tinkering by natural selection produced AFP II (11) and AFP III (12), respectively.

No mention at all of constructive neutral evolution. Pure adaptationist thinking.

(Tiberius Claudius Caesar Augustus Germanicus) #4

Gene duplication is mentioned as part of the story. That would be neutral wouldn’t it?


That would be the random mutation part of mutation/selection. It’s not an alternative to selection, as neutral evolution is supposed to be.


Sometimes gene duplication is neutral, sometimes it is not. Gene duplication can increase the amount of protein that is produced which can have an impact on fitness in some cases.

(Tiberius Claudius Caesar Augustus Germanicus) #7

I meant that a gene duplication may often be selectively neutral, because you’ve just got a copy of something you already had. The paper may not use the words ‘neutral’ but they refer to an equivalent process.

@T_aquaticus pointed out that sometimes a duplication results in increased protein production, so not all duplications will necessarily be neutral. But it seems plain that many will be.

(Mikkel R.) #8

A significant portion of the sequence of events involved multiple mutations, including duplicates, before the reading frame acquired a promoter, so they would have been neutral before this stage. That’s textbook constructive neutral evolution.

The selection came after transposition into an area under control of an active promoter, where additional subsequent microsattellite expansions of the Thr-Ala-Ala region became advantageous.

So it’s actually a combined process. First a period of constructive neutral evolution, and then followed by cumulative selection.

(Jordan Mantha) #9

Blows my mind. At this point I can’t even fathom how complex this all is, simply amazing! I have so many questions, but they are so basic I need to spend some time with a molecular genetics textbook.