Some research indicates amplification effects are common and often render duplication mutations favorable.
The results of this analysis indicate that recently duplicated paralogs evolve faster than orthologs with the same level of divergence and similar functions, but apparently do not experience a phase of neutral evolution. We hypothesize that gene duplications that persist in an evolving lineage are beneficial from the time of their origin, due primarily to a protein dosage effect in response to variable environmental conditions; duplications are likely to give rise to new functions at a later phase of their evolution once a higher level of divergence is reached.From here.
One of the more spectacular examples is this one, which gore has seen and forgotten dozens of times. Other people have other implausible excuses for ignoring it.
Gene duplication appears to have occurred so many times that there must have been some initial advantage in some instances, even if the effects were indirect. Thanks for the links.
From here.
One of the more spectacular examples is this one, which gore has seen and forgotten dozens of times. Other people have other implausible excuses for ignoring it.
Please read your first link and explain this.
The inconsistency of empirical evidence with Ohno's model prompts questions on the validity of some of the assumptions underlying this model. One major assumption, which was inherited by the subfunctionalization model, is that one gene copy is sufficient to perform the respective function, so that a gene duplication is redundant and has no effect on fitness [1,10]. This notion has been widely accepted, and often becomes one of the central postulates of models of duplicated gene evolution [3,7,26,27]. Should this be the case, however, a duplication event would only very rarely achieve fixation [28,29]; moreover, in the event that a duplication is slightly deleterious, it would be effectively prevented from achieving fixation [30]. Although the notion of duplication producing redundant genes is central to current theories of duplicated gene evolution, the short-term benefits of gene duplications are well known. This is illustrated by the numerous observations of adaptive gene amplifications in response to antibiotics [31,32,33], anticancer drug treatments and exposure to various toxins [34,35,36,37,38,39] or heavy metals [40,41,42,43,44], nutrient limitations [32,33,45,46,47,48,49,50], pesticide treatments [51,52,53], extreme temperatures [54,55] and symbiotic and parasitic interactions [56,57]. Combining this information with the observations that recently duplicated genes evolve under purifying selection ([21] and our present work), it seems reasonable to hypothesize that a majority of duplicated genes that achieve fixation in a population increase fitness when present in two or more copies in a genome and thus are subject to purifying selection from the moment of duplication. Recently duplicated paralogs appear to be a nonrandom group enriched in genes coding for proteins involved in different aspects of the organisms' interaction with the environment (see Additional data files). In particular, a substantial fraction of these paralogs encode (predicted) membrane or secreted proteins. |
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