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Recombination and the evolution of diploidy
1Department of Biological Sciences, Stanford University, California 94305.
Genetics
|July 1, 1992
Summary
Diploidy, having two gene copies, masks harmful recessive mutations. This study shows diploidy evolves when masking is effective, but requires significant genetic recombination, especially in organisms with alternating haploid and diploid phases.
Area of Science:
- Evolutionary biology
- Genetics
Background:
- Diploid organisms possess two gene copies, enabling the masking of deleterious recessive mutations.
- Organisms with alternating haploid and diploid phases (alternation of generations) face evolutionary pressures regarding ploidy level.
Purpose of the Study:
- To analyze a two-locus model to determine conditions under which masking of deleterious alleles favors the evolution of a dominant diploid phase.
- To test the 'masking hypothesis' which posits that diploidy is favored when masking occurs.
Main Methods:
- Analysis of a two-locus population genetics model.
- Mathematical and analytical methods to evaluate the favorability of diploidy over haploidy.
Main Results:
- The masking hypothesis is largely supported under conditions of free genetic recombination.
- Diploidy is favored when wild-type alleles effectively mask the heterozygous expression of deleterious alleles.
- Lower rates of recombination significantly reduce the likelihood of diploidy evolving.
Conclusions:
- Significant genetic recombination is crucial for the evolution of diploidy, even with strong masking of deleterious alleles.
- The evolution of diploidy may be impossible without substantial recombination, according to the model presented.