Pleiotropy and multilocus polymorphisms

Article Abstract:

An analysis was conducted to determine the number of polymorphic loci that can be maintained in a system of two pleiotropically related characters. The results showed that in this type of system, under Gaussian selection, a stable polymorphism in a number of loci exceeding the number of characters can be maintained. A high level of polymorphism can exist if the selection pressure on the population is not very weak. This degree of polymorphism may not be reflected by a high degree of pheontypic variation because of the negative linkage disequilibrium generated between the loci. In fact, multiple stable equilibria are possible under stabilizing selection.

Variation (Biology)

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Population genetic models of genomic imprinting

Article Abstract:

The population genetics implications of several models of genomic imprinting were investigated. Systems incorporating imprinting did not have to behave in the same manner as those without, but many of the models could be shown to be formally equivalent to models without imprinting. These equivalences imply that imprinting cannot be detected by mere analysis of gene frequency changes. Based on these observations, a phenomenon called pseudoheterosis was defined as a condition where an imprinting system without heterozygote advantage behaves in an equivalent manner to a non-imprinting system with it.

Research, Genetic aspects, Gene expression, Sex differences

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Models with mutation from existing alleles, part 4

Article Abstract:

The level of polymorphism in a simulated population bombarded with lethal mutations was monitored through several generations. Allele frequencies were iterated simultaneously, which allowed mutant alleles to be driven to extinction by selection. Under these theoretical conditions, a high level of polymorphism could evolve. Even alleles that are lethal in homozygous doses could evolve to high frequencies. The results were interpreted in terms of the neutralist and selectionist theories of evolution.

Mutation (Biology), Mutation, Lethal mutation

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