Provides genetic evidence that Caenorhabditis elegans lin-13, a member of the LIN-35 Rb class of genes involved in vulval development, behaves as a class B SynMuv genes. Genetic interactions of lin-13 with Synmuv genes; Molecular cloning and sequencing of lin-13; Genetic properties of lin-13; Role of SynMuv genes in vulval precursor cell specifications.