An unexpectedly large proportion of eukaryotic genes yield no obvious mutant phenotype when inactivated. An ingenious new approach using yeast allows all genes to be screened simultaneously for the presence of weak selection against lack-of-function mutations.
Brookfield, J. F. Y. (2004). Genetic redundancy: Screening for selection in yeast. Current Biology, 7(6), R366–R368. https://doi.org/10.1016/s0960-9822(06)00176-x