Lecture 33: Using yeast as a model organism

(version 31 October, 1999)

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Saccharomyces cerevisiae - bakers yeast

Why yeast?

1.        Simple, unicellular eukaryote

2.        Very easy to grow and manipulate

3.        Great genetics:

a.    Haploids grow mitotically, making it easy to isolate recessive mutations:

b.    Haploids mate to form diploids, which also grow mitotically.  Makes it very easy to determine whether mutations are dominant or recessive, and to do complementation testing.

c.     Diploids undergo meiosis and sporulation when starved. Makes it very easy to analyze linkage between different mutations (recall Bruce's lectures on tetrad analysis).

d.     Small genome (~6000 genes) that's already been sequenced

e.     Homologous recombination occurs most of the time, so gene knock-outs etc are simple.

An example of using yeast to understand human disease: Colon cancer in humans is caused by mutations in genes that are required for DNA repair.  Yeast DNA repair mutants led to this discovery.