or the yeast Saccharomyces cerevisiae. Such organisms exist normally in a haploid state, containing only one set of chromosomes per cell. However, the mechanism remains largely the same among all haploid eukaryotes.

When subjected to environmental stress, such as nitrogen starvation in the case of Chlamydomonas, cells are induced to form gametes. Gamete formation in single-celled haploid organisms such as yeast is called