Predict the results of a cross between ascospores from a segregational petite strain and a neutral petite strain. Indicate the phenotype of the zygote and the ascospores it may subsequently produce.

Key Concepts

Segregational Petite Strain

A segregational petite strain refers to a type of yeast that has a mutation affecting mitochondrial function, leading to a petite phenotype characterized by reduced growth and altered energy production. In these strains, the petite phenotype can segregate during meiosis, resulting in offspring that may exhibit either the petite or wild-type phenotype depending on the genetic makeup inherited from the parents.

Neutral Petite Strain

A neutral petite strain is a variant of yeast that also exhibits a petite phenotype but does not have a segregational mutation. Instead, its petite characteristics are typically stable and do not segregate during reproduction. This means that when crossed with other strains, the neutral petite strain will consistently produce offspring with the same petite phenotype, providing a contrasting genetic background to the segregational petite strain.

Zygote and Ascospores

In yeast, a zygote is formed when two haploid cells fuse, resulting in a diploid cell that can undergo meiosis to produce ascospores. Ascospores are the haploid spores produced by the meiotic division of the zygote, and their phenotypes depend on the genetic contributions from both parent strains. The phenotype of the zygote and the resulting ascospores will reflect the combination of alleles inherited from the segregational and neutral petite strains.