Examining the relationship between ploidy and cell growth using budding yeast in the undergraduate cell biology laboratory

Ploidy is a key determinant of cellular physiology, influencing genome content, cell size, and metabolic requirements. In <i>Saccharomyces cerevisiae</i>, differences between haploid and diploid strains provide a tractable system for investigating how genome duplication affects population growth dynamics. This article describes an upper-level undergraduate laboratory module in which students examine the relationship between ploidy and cell growth using high-throughput optical density (OD₆₀₀) measurements. Haploid and diploid yeast strains are cultured in a 96-well plate format, and OD₆₀₀ is recorded every 20 min over a 24-hour period using a plate reader. The experimental design incorporates standardized starting densities, serial dilutions, and biological and technical replicates, enabling students to generate and analyze growth curves. Students analyze the resulting data using statistical methods to identify growth phases, calculate doubling times, and assess how ploidy influences growth dynamics in conditions of interest. This module helps students connect microbial growth concepts with data analysis tools and software. The module facilitates an understanding of quantitative analysis, hypothesis testing, and engagement with primary literature. The module provides a flexible framework for integrating data-driven experimentation into the cell biology curriculum, with adaptability for exploring environmental variables and reinforcing core competencies in scientific inquiry.