Thousands of human genomes are being sequenced at an unprecedented rate, ushering in an era of extraordinary data generation that is revealing a multitude of genetic variants within individuals. However, a large proportion of these variants have unknown functional importance, which presents the formidable challenge of discerning any potential health implications of each sequence alteration. To address this challenge, researchers have turned to synthetic biology to functionally replace human biological processes in a simplified cellular setup, such as Saccharomyces cerevisiae (baker’s yeast), generating ‘humanized yeast’. The underlying principle of humanized yeast involves substituting yeast genes with their disease-associated human counterparts. This substitution enables the fitness of a variant human protein to be linked to the overall fitness of the yeast cell, especially when the gene is essential for optimal growth and survival. This cost-effective approach (which is also faster than traditional methods such as animal studies and clinical trials) provides a surrogate system for the mechanistic exploration of human gene function, the effect of genetic variation on function and drug discovery at scale.