Yeast as a Model Genetic Organism [23]

 

The budding yeast Saccharomyces cerevisiae has emerged as a versatile and robust model system of eukaryotic genetics. Mutant screening and segregation analysis are simpler and easier to perform in yeast than in multicellular organisms and fundamental eukaryotic biology. Yeast has a high endogenous rate of homologous recombination, and a host of extrachromosomal DNA elements can stably transform yeast cells. Thus the analysis and cloning of genes in this organism is significantly easier than in more complex eukaryotes.

 

The Budding Yeast as a Typical Eukaryote

As microorganisms, yeasts are grown in batch liquid culture and isolated as colonies derived from single cells on solid media. The generation time is very short (about 90 min), so large populations of individuals can rapidly be grown and analysed. This is crucial in addressing many problems in genetics that require the observation of rare events, such as genetic mutations.

 

How Yeasts Became Popular Model Systems

As a domesticated microorganism and sexual eukaryote, the budding yeast Saccharomyces cerevisiae is the most commonly used industrial yeast and has emerged as a remarkably tractable eukaryotic model system. The budding yeast found an early role in metabolic research owing to its association with the fermentation industry. Early geneticists soon found a variety of unicellular fungi useful in demonstrating the underlying genetic control of metabolism, and thus established techniques to order genes along chromosomes and into pathways. Mutations in metabolic genes soon became useful as selectable markers for genetics, acting as indicators of a strain’s genotype. An important theme of yeast biology is the use and study of homologous recombination, a process by which a broken piece of DNA uses a homologous DNA template as a substrate for repair. Yeast use this process to fix DNA damage, to switch mating types, and to segregate homologous chromosomes during meiosis. Researchers also use this pathway for genetic mapping and integrative transformation of DNA into specific locations of the genome.