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Yeast Genetics Workshop

Introduction

Yeast genetics nomenclature:

In order to follow the yeast literature, one needs to be familiar with the language of yeast genetics. It is very important to be able to accurately distinguish between yeast strains, phenotypes, genes and proteins. The following rules offer an introduction to yeast nomenclature.

Genes: with the exception of the mating locus genes Mat a and Mat a, yeast genes are written in italics, and they are designated by three letters and a number (i.e. URA3, CDC44, LEU2 etc.). The letters could represent an acronym for a function of the respective protein (i.e. uracil or leucine biosynthesis) or else they may have no obvious meaning.

Wild type (normal) genes have only the three letter, one number designation. Wild type genes can also be indicated by a ‘+" symbol.

If a gene is not indicated, it is assumed to be wild type
Mutant genes carry an allele number or designation that uniquely identifies the sequence change. There are many kinds of allele designations. Some are simple numbers (i.e. ura3-52), others indicate deletions in the gene (leu2 delta 1)

Dominant genes are written in uppercase: CDC44

Recessive genes are written in lowercase: cdc44-1

Proteins: yeast protein names follow the names of the genes that encode them. However, they are not written in italics, only the first letter is capitalized, and they may be followed by the letter ‘p’. For example:

Leu2p : represents the protein encoded by the wild type LEU2 gene

Cdc44-1p: represents the protein encoded by the mutant cdc44-1 gene

Phenotypes: a phenotype is a property of a yeast strain. Strains that carry mutations which prevent them from growing at high temperatures are temperature sensitive (ts^-). Strains that carry mutations that prevent them from growing in media without adenine are Ade^-.. Many phenotypic designations exist. In general, the minus (-) superscript means that a strains is defective in a certain process, the plus superscript (+) means that it is proficient.

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