Strong loss-of-function or null mutants can sometimes lead to a penetrant early lethality, impairing the study of these genes' function. This is the case for the
ceh-6 null mutant, which exhibits 100% penetrant lethality. Here, we describe how we used gene bashing to identify distinct regulatory regions in the
ceh-6 locus. This allowed us to generate a
ceh-6 null strain that is viable and still displays
ceh-6 mutant Y-to-PDA transdifferentiation phenotype. Such strategy can be applied to many other mutants impacting viability.