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Can someone tell me where can I find detailed text about mechanisms of evolution of dominance? Or, if it is possible, I would be grateful if someone will tell me about them here.

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  • $\begingroup$ Why was it downvoted? Because it is asking for both (it is a either or format actually) a book-recommendation and a review? $\endgroup$ – Remi.b May 2 '15 at 22:00
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    $\begingroup$ And do you have any particular theory in mind? YOu might want to read this for background knowledge ( Bourguet, Denis. "The evolution of dominance." Heredity 83.1 (1999): 1-4. ) $\endgroup$ – Rover Eye May 2 '15 at 22:01
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Welcome to Biology.SE!

I am not aware of any book that talks extensively about the evolution of dominance. It is a very interesting field of research. You can probably search for papers on the subject that will go much further than my below answer. For example, you may want to read Mayo and Burger (1996), Bourguet (1999) and Billiard and Castric (2011) I hope that my answer below can provide the ground for more searching by presenting the two main (and of historical importance) hypotheses.


There are several hypotheses about the evolution of dominance. It is important first of all, to note that empirical observations show that beneficial alleles tend to be more dominant than detrimental alleles. There are a number of hypotheses and I won't be able to make a complete review. Among the two main hypotheses to explain the evolution of dominance, one has been formulated by Ronald Fisher and one by Sewall Wright (and J.B.S Haldane).

Fisher's hypothesis

According to Fisher's hypothesis, between two equally beneficial alleles, if one is more dominant than the other than it's heterozygote carrier will have higher fitness. In consequence, beneficial alleles evolve to become more dominant while detrimental alleles evolve to be recessive (so that they can hide from selection in heterozygotes). The main criticism to this model is that selection for dominance is possible only when the locus is polymorphic. This means that the strength of selection for dominance is of the level of the mutation rate, seemingly way too weak to explain the observed pattern of dominance.

Wright's hypothesis

According to Wright's hypothesis, beneficial alleles are more dominant because of the kinetic of biochemical reactions. The rate of a biochemical reaction is a function of the concentration in the substrates of interest. The function is called "Michaelis-Menten function" after the name of the authors. The Michaelis-Menten function looks like this:

enter image description here

Think about a knock-out mutation. Such mutation will decrease by half the concentration of protein the gene in question produce in heterozygotes. Imagine, the concentration of proteins in the wildtype homozygote was 3 (see above graph). The rate of reaction of this homozygote is therefore about 3. The heterozygote would have a concentration of 1.5 and the rate of the reaction is therefore about 2.5-2.75. Assuming that the rate of this biochemical reaction is directly related to fitness, then a the locus of interest, benefical alleles are necessarily dominant and detrimental alleles are necessarily recessive. Selection for dominance is not involved in Wirght's model.

In addition to that, if you have a series of biochemical reactions, you will likely have one reaction that is causing a bottleneck. One reaction that is the limiting factor of the speed of some biochemical pathway. Let's call this reaction process A. If a mutation occurs on a gene coding for any other reaction process B that is not the limiting factor (process A), then this mutation will have no effect on fitness as long as it is not important enough to make process B slower than process A. This may lead to pattern of dominance. I am not quite sure by how much of this has been formulated by Wright and Haldane though.

Is Fisher's or Wright's hypothesis correct?

To my understanding, current state of the art is to consider Wright's model to be correct and Fisher's model to be wrong. In reality, the truth probably lies somewhere in between these two extremes. There exists more detailed (and more mechanistic) models of the evolution of dominance that and the above dichotomy might not be very representative of the current debate on the subject. For example, I (vaguely) remember that during my undergrad, Sylvain Billiard gave a talk at my university in which he reported that some alleles actually have some domain that are directly responsible for decreasing the expression of the other allele on the sister chromosome suggesting that Fisher's hypothesis might sometime be quite a good explanation as well.


This answer was recycled from what I wrote here. But it is a much better fit to your question than to where it was originally posted.

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