Figure 1. The life cycle of Saccharomyces cerevisiae. (a) Alternation of generations and vegetative growth. (b) Mating type switching in homothallic ( Ho⁺) haploids. Mother cells switch in G₁.

Figure 2. Meiotic segregation in the budding yeast. (a) Cross between two mutants, yfg1 × yfg2. The white and black boxes represent the mutant alleles of yfg1 and yfg2, respectively. The black circle represents the centromere. (b) Schematic of chromosomes after DNA replication and the pairing of homologous chromosomes. (c) Schematic of three possible chromosome configurations after recombination and synapsis. CO stands for crossover. (d) Tetrad classes resulting from a given crossover event are represented with the genotype indicated in the spore. Not shown: two-strand double crossovers result in PD; three-strand double crossovers result in T.

Figure 3. Schematic of targeted transformation by homologous recombination. (a) Plasmid integration. (b) Allele replacement. (c) Plasmid gap repair by homologous recombination.