Evolution of new genes vs gross changes in physiology

[Sarahmay]

As I understand, the underlying mechanism of the formation of
new genes must first consist of a gene duplication event. This results in one gene constrained to its original function whereas the other gene is removed from the pressure of selection thereby allowing it to drift/be selected for change either to produce a specialised but similar function or a entirely new
function. Where often this is followed by exon shuffling. I understand this at a protein level. New kinases for instance or the evolution of haemoglobin.

However, when trying to apply this idea to the macro view of evolution, confusion arrises. Take the evolution of the mammalian ear bones. These originally evolved from the gills of fish, became part of the jaw bones in jawed fish, a way of detecting vibrations in the jaws of reptiles and finally a way of amplifying sound waves in mammals. What is happening, in this case, on a molecuar, DNA level. Are mutations occuring in the genes of the bones? The promoters of these genes? Transcription factors which control the development of the bones? Did gene duplication have to occur in this case? Presumably there was not a organism with two bones, one serving its orginal function, say supporting the gills, and the other serving a new function, which would be as a jaw? Simultaniously?

[POLLITO110]

Gene duplication is not the only way of speciation, inversion and translocation may be also very important (where chromosoms change his shape).

http://www.biology-online.org/2/8_mutations.htm

 

 

 

 

 

 

 

 

 

 

 

 

Presumably there was not a organism with two bones, one serving its orginal function, say supporting the gills, and the other serving a new function, which would be as a jaw? Simultaniously?

 

There are a lot of DNA configurations with aberrating results, and one could be have two bones of each kind. What happens is that as soon as the egg is fecunded and the embryo has a lethat genetic configuration (ie, no chromosom 21 in humans), pregnancy does not go ahead. It's the same that happens when a dog and a cat mate (Chromosoms do not match because they are genetically incompatible).

 

 

 

[CharonY]

Duplication events are not a necessity, unless of course the gene in question is under selective pressure.

 

 

However, when trying to apply this idea to the macro view of evolution, confusion arrises. Take the evolution of the mammalian ear bones. These originally evolved from the gills of fish, became part of the jaw bones in jawed fish, a way of detecting vibrations in the jaws of reptiles and finally a way of amplifying sound waves in mammals. What is happening, in this case, on a molecuar, DNA level. Are mutations occuring in the genes of the bones? The promoters of these genes? Transcription factors which control the development of the bones? Did gene duplication have to occur in this case? Presumably there was not a organism with two bones, one serving its orginal function, say supporting the gills, and the other serving a new function, which would be as a jaw? Simultaniously?

 

There is not one gene that controls the formation of a single bone. Often, a simple duplication has little phenotypic change, especially at the beginning and even the production of an aberrant protein could be neutral in outcome. So one should step a little bit back from the imagery that a single gene controls a specific phenotype (if that was implied).

 

Of course many genes act in concert and their expression in time and space together with certain environmental factors finally result in the development of certain phenotypes. From that point of view, you are correct in the notion that regulatory changes are going to have a much stronger impact. Indeed, developmental studies show that precisely to be the case.