Abstract
The biological phenotype is affected by the level of gene expression. Here, we provide a step-by-step protocol for precisely titrating and quantitatively observing the target gene expression level in budding yeast by manipulating its copy number in the genome. Using this method, we construct various strains with different gene copy numbers of the cell cycle inhibitor Whi5. This protocol enables stable and inherent control of gene expression at the expected level with fluorescent intensity as the quantitative readout. For complete details on the use and execution of this protocol, please refer to Qu et al. (2019).