A duplicated gene will have all of the promoter elements necessary for its expression.
This is just wishful thinking on your part and not fact. There is no reason at all why such a thing would happen in a random mutation. In addition you do not seem to fully understand the problem. Different functions require different kinds of cells. You need to have cells assigned to do the gene's work and to be of the proper constitution. A new gene, even a duplicate would not possibly have such a thing in the genome. In addition to which if it was just a xerox copy, it just would at most double the functioning of the old gene which is very likely to be harmful.
This is just wishful thinking on your part and not fact. There is no reason at all why such a thing would happen in a random mutation. -you
Not wishful thinking at all. It is entirely plausible that the promoter remains intact after gene duplication. Initially, you have simply duplicated an entire stretch of DNA and end up with an identical copy with promoter, introns and the whole shebang.
A new gene, even a duplicate would not possibly have such a thing in the genome.
Completely flase assumption. I gave you several examples where amplification of a gene product could be beneficial. It could also have an indirect effect on the phenotype. In the case of an amplified gene, you already have the machinery in place in the appropriate cells to handle the augmentation in expression.
In addition to which if it was just a xerox copy, it just would at most double the functioning of the old gene which is very likely to be harmful.
Why would it be necessarily be harmful? On what are you basing your assumptions?
Even if the amplified gene is completely neutral, there should be instances where the duplication happens to occur on "good" DNA carrying alelles which already endow the organism with a better chance for survival. If they are close enough to each other they are effectively linked.
Do you really know what you are talking about here Gore? Have you ever worked with transgenic mice? I can think of one example where a gene was engineered to be overexpressed and in the "on" state continuously. Not only that but the gene product was constituitively active! The mice were FINE.