2012 Student Scholarship Highlights
Chavez, Julissa '13
How to Cheat at Sex and Win: Meiotic Drive in Fission Yeast
Speciation occurs when related organisms evolve to no longer interbreed and produce fertile offspring. S. pombe(Sp) and S. kambucha(Sk) are normally haploid species, but can mate to produce viable hybrid diploids. Although viable, the hybrid diploids are largely infertile when compared to pure species diploids. This decreased fertility is partially due to unfair sexual reproduction through which the Sk alleles are transmitted at greater than 50% to the progeny, exhibiting meiotic drive. Meiotic drive leads to genetic conflict though an evolutionary arms race between the driving alleles and suppressors, causing rapid evolution and eventually speciation. Sp/Sk hybrids produce progeny that inherit Sk alleles at a greater frequency than Sp alleles, but this Sk drive is not due to differential viability of haploids. This brings to question the basis of this biased inheritance. Is drive drive phenotype genetically or epigenetically inherited? Various recombination-independent haploid S. kambucha, S. pombe, and hybrids were mated to produce genotypically identical diploids and then put through meiosis to assay their progeny. The progeny had different genotype frequencies despite genotypically identical diploids, depicting that meiotic drive phenotype has an epigenetic basis. One haploid cross did not exhibit drive, suggesting that meiotic drive phenotype can be eliminated epigenetically and that the genotypes of the haploid parents, rather than the genotype of the diploid, affects the meiotic phenotype of the progeny.
This work was supervised by Harmit Malik (Fred Hutchinson Cancer Research Center & the HHMI)
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