Aneuploidy in the budding yeast Saccharomyces cerevisiae

Hello everyone,

My name is Zach Oppler and I’m a rising junior here at William and Mary. I’m a CAMS (biology track) and Psychology double major and I’m from Potomac, Maryland. This semester I worked in Dr. Murphy’s evolutionary genetics lab and that’s where I’ll be working this summer as well.

I work with the yeast Saccharomyces cerevisiae which is commonly used as a model organism in biomedical research because it is a relatively simple eukaryotic organism with an extremely quick cell cycle that allows us to perform experiments over many generations in a short period of time. The goal of my project is to determine whether aneuploidy causes negative genetic incompatibilities or confers a selective advantage that allows cells to survive and reproduce better in stressful environments.

Aneuploidy often has a negative effect: Extra copies of chromosomes can result in overexpression of what are normally carefully regulated genes.  Aneuploidy is a typical characteristic of cancer cells and in humans it can result in several other diseases, such as Down’s syndrome (an extra copy of our 21st chromosome) as well as Edwards’ syndrome (an extra copy of the 18th chromosome). Despite the negative effects of aneuploidy, it is frequently found in nature and can sometimes confer a benefit.

This summer I will be characterizing the ploidy state of several replicate populations, as well as specific individuals from these ending populations. The presence of aneuploidy can be determined using quantitative PCR by judging the amount or the speed at which DNA is replicated. If the starting amount of DNA is greater, the total amount of DNA being replicated will grow much faster, suggesting that an extra chromosome is likely present. On the other hand, if the starting amount of DNA is smaller, it will replicated much more slowly, suggesting that a chromosome is probably missing.
The ultimate goal of my research is determine whether several replicate populations that evolved fastest when challenged with a harsh environment were aneuploid or euploid. This research will contribute to our understanding of the effect of common chromosomal abnormalities both in humans and natural populations of plants and animals.