Final Summary

This summer went by fast! I feel I have accomplished a lot!

The goal of my project was to determine if genes required for sexual reproduction are undergoing selection to facilitate speciation in the yeast Saccharomyces paradoxus. Saccharomyces paradoxus is woodland yeast found in Europe and North America. In a previous lab, my advisor found evidence of speciation in this yeast. In a recent migration event, a European Saccharomyces paradoxus population migrated to North America. This Migrant population exhibited mating discrimination towards potential North American mates while its ancestral European populations did not. This behavior likely evolved in the Migrant population to avoid reproducing with genetically incompatible North American potential mates, as the offspring of inter-population pairings were substantially less viable. This served as evidence for speciation.

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Last Week: Dissection and Replica Plating

This past week, I’ve been performing dissections with the yeast I have successfully transformed. Before the yeast can be dissected, they must undergo sporulation, forming four haploid spores. In a dissection, I separate the spores, placing them in columns on a YPD plate. The picture below is from one of the dissections I performed.

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Yeast Transformations

The goal of my project is to determine if the evolution of sexual agglutinin genes is a possible mechanism behind speciation. These past two weeks, I’ve been performing transformations to insert the sexual agglutinin genes I am analyzing into European, Migrant and North American strains of Saccharomyces paradoxus.

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Preparation for Allele Swapping

This summer, I am researching possible mechanisms behind speciation in the yeast Saccharomyces paradoxus. I hope to determine if the evolution of sexual adhesin genes, which are required for sexual reproduction, drives speciation. Recently, there was a migration of a Saccharomyces paradoxus population from Europe to North America. This migrant population has displayed evidence of speciation in its mating preferences. In my project, I am analyzing the mating behaviors of North American, European and migrant strains after switching sexual adhesin alleles among the different populations.

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Abstract: The Role of Sexual Adhesins in Yeast Speciation

Hello, my name is Rachel and I’m a junior at the College. This summer, I will work in the Murphy lab to investigate speciation in populations of the yeast Saccharomyces paradoxus. Speciation is the evolutionary process by which new and distinct species arise from a single species. Usually, one population splits into two, and the populations diverge from one another until they can no longer reproduce successfully if they come back into contact. In my project, I will investigate the mechanisms and genetic basis of speciation in eukaryotic microbes. Specifically, I am interested in determining if genes required for sexual reproduction are undergoing selection and preventing diverging populations from mating with one another, completing speciation.

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