The product of the maternal skn-1 gene is required for specifying the identity of one 4-cell stage blastomere called EMS. In embryos that do not receive skn-1 (+) gene product, EMS instead develops more like its sister P2, ultimately resulting in dead embryos. In a genetic screen for dominant suppressors of a weak but non- conditional allele of skn-1, zu129, we identified one animal out of about 100,000 in which an apparently homozygous zu129 mother produces all viable embryos. Preliminary studies suggest that the suppressor, or50, is extragenic but on the same chromosome as skn-1 (LGIV). Experiments are underway to determine if the suppressor is allele specific and if it has a phenotype in a skn-1 (+) background. We are also sequencing the skn-1 allele in the suppressed strain to verify that the original mutation (a stop codon) is still the only skn-1 mutation present.