Heterozygotes are Unc and express myo-2::GFP in the pharynx. spe-42(tn1231) homozygotes are non-Unc and non-GFP. spe-42(tn1231) produces <1 self progeny at 16C and no self progeny at 25C. The Spe defect can be rescued by WT sperm. Homozygous nT1[unc-?(n754) let-? qIs50] are embryonic lethal.