RAPID LOSS OF DUPLICATE GENE-EXPRESSION BY NATURAL-SELECTION

Theoretical studies of the rate of fixation of null alleles at duplicate loci were carried out with both deterministic numeric analysis and computer simulations assuming an intermediate selective optimum of the number of active gene copies. A relatively rapid loss of duplicate gene expression occurs with this model under a wide variety of conditions, including incomplete recessiveness of the null allele and linkage. It differs from previous models of gene loss, which are based on mutation pressure, because the rate of gene loss is accelerated with increasing population size. Identification of the mode of selection responsible for the observed loss of gene duplication in polyploid fish is not possible at present. It appears, however, that the loss of duplicate gene expression occurs shortly following duplication. Once some structural or regulatory genetic divergence occurs, the duplicated loci become relatively stable. © 1979 The Genetical Society of Great Britain.