Design and practice of educational experiments on genetic epistasis.

Genetic epistasis is a fundamental concept in genetics that describes how interactions between genes determine phenotypic traits. To enhance students' understanding and practical application of genetic epistasis, this experiment is designed and conducted using gene mutations in the adenine biosynthesis pathway of (baker's yeast). is a classic model organism for genetic teaching experiments. In its adenine biosynthesis pathway, a mutation in the gene leads to the accumulation of the intermediate 5'-phosphoribosylaminoimidazole (AIR), causing the cells to appear red. However, if a gene upstream of in the adenine biosynthesis pathway (such as ) is defective, the red phenotype of yeast will disappear. Conversely, a defect in a gene downstream of (such as ) does not alter the red phenotype. Therefore, is epistatic to In this experiment, the CRISPR-Cas9 genome editing technology is employed, allowing students to perform single knockout of Δ, as well as double knockouts of ΔΔ and ΔΔ in . By observing the phenotypic changes in yeast mutants from white to red and back to white, students gain a profound understanding of the basic genetic theory of how genes determine phenotypes and the concept of epistasis in gene interactions. This experiment also enables students to master fundamental yeast genetic techniques, significantly enhancing their ability to design and conduct experiments in real research environments. This is of great significance for their future research work and academic development.