Duplication – notes

gene duplication or phenotypic duplication

“Duplication leads to divergence only if duplicated parts are independently expressed. Only then can traits become developmentally independent of other copies and independently subject to variation and expression.”

all levels of phenotypic organization, serial duplication only [gene duplication has other kinds of duplication], also pleiotropy as the duplicated expression of genes

“It is a difference in regulation, then, that causes duplicates to diverge phenotypically and ultimately renders them subject to diverging selection and divergent evolution”

“not only the parts are duplicated, but many factors that might influence their development and activity are duplicated as well”

Rule of Independent Selection

“duplicates can have three different fates: they may be used as duplicates, as in multigene or multiphenotype families, where multiple copies increase product quantity; they may diverge, as in the case of embryonic and fetal globin genes; or they may become nonfunctional, for example, yielding the so-called pseudogenes”

“Any difference in the environment, phenotype, location, or use of duplicates sets the stage for different regimes of selection and the divergent evolution of duplicate traits”

Gene Duplication

adaptive divergence of duplicated genes: the chalcone synthase (CHS) gene family which influences flower color in morning glories

“The divergence of homeobox genes exemplifies divergence promoted by spacial differences in expression”

“Duplication followed by combinatorial evolution of initially identical useful genes permits reuse of already functional genes while allowing them to evolve in new contexts”

escape from conservatism without disturbing function

Duplication in the Origin of Novel Morphologies

arthropods: segment multiplication followed by specialization of different segments, in parallel with homeobox duplication

evolution of endosperm in plants

Duplication in the Origin of Novel Behaviors

sexual displays – Sensory traps, Sensory exploitation

“Hundreds of proposed examples of manipulative behavior duplication are found in the details of courtship and copulation in animals”

social displays

Concerted Evolution and Diversification in Multigene and Multiphenotype Families

“Iterative duplication creates families of traits of two general kinds: sets of identical traits and sets of divergent serially homologous traits”

Concerted evolution, or a synchronous series of changes in nucleotide sequence among the members of a multigene family, can occur by various mechanisms such as gene conversion, the transfer of DNA between nonallelic genes”

duplication of a diverged duplicate

“distinct subfamilies can evolve when a subset comes under independent control”

“when twice the mutation rate is larger than one tenth the conversion rate, the two duplicate genes will be sufficiently different to evolve independently”

“When … such correlation among parts have adaptiv connsequences, selection would reinforce concerted change in the duplicates, forming multiple phenotype families.”

“The production of large amounts of yolk proteins is preceded by the many-fold duplication of the expressed genes. Does a history of such ‘programmed’ duplication ever promote structural changes in DNA that might increase the susceptibility of a germline gene for duplication?  If certain genes evolve under selection for increased facility of duplication,  it is conceivable that the same properties could facilitate their duplication in the germ line”

multiple eyespots expressed in the wet season but not the dry

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