Yeast Home Page

Research Based Labs with Yeast

Yeast Life Cycle and Basic Genetics

Radiation Effects on Yeast

Red and White Yeast: An Introduction to Science as a Process

Transformation of Yeast

Research Based Labs with Yeast

The yeast Saccharomyces cerevisiae is particularly well suited for exploration of the principles of basic genetics because it has a complete sexual cycle and numerous nutritional mutations that serve as markers, allowing segregation of traits to be readily followed in crosses. A brief review of the yeast life cycle follows below.

Another area offering the potential for extensive investigation is the behavior of yeast when irradiated or treated with other DNA damaging agents; experiments include basic radiation biology and genetics of radiation damage repair.

Yeast is also readily transformed with plasmids and chromosomal DNA fragments and this method of genetic manipulation lends itself to a number of studies.

Yeast Life Cycle

Saccharomyces cerevisiae is a unicellular fungus that grows on simple nutritional media. The first strains cultivated were cultured from grape skins. Yeast can grow vegetatively as either haploids or diploids and both phases are stable but it is also easy to manipulate haploids to form diploids and vice versa. There are two sexes, or mating types, a and (alpha). These are controlled by alleles of a single genetic locus, MAT, the mating type locus. Mixing together a and strains stimulates them to secrete pheromones that cause the cells of opposite mating type to form elongated projections that then allow fusion of a and to form a/ diploids. Such diploids will then grow vegetatively unless starved for nitrogen. In this instance, they will initiate the process of meiosis, followed by spore formation. The four haploid cells resulting from each meiosis are spores and are encased in a sac called the ascus. This packaging of the products of individual meioses is what has made yeast and other ascomycetes (ascus-forming fungi) such valuable organisms for genetic research. Two of the spores in each ascus will give rise to a cells and two to cells when they are placed on nutritionally adequate medium. These are the source of new haploid strains of yeast. The yeast cell division cycle has been the subject of intense investigation and is very similar to that of higher eukaryotes. For more detailed information about the yeast life cycle see Baker's Yeast and Its Life Cycle at the GENE web site.

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March 28, 2001