such-5 is an uncloned gene, whose allele such-5(h1987) suppresses the long-term sterility (over two to three generations) of homozygous mdf-1(gk2) mutations; unlike such-1 through such-4 mutants, in mdf-1(gk2);such-5(h1987) mutants neither germline nor early embryonic mitosis is delayed, nor is X chromosome missegregation decreased; such-5 is required for progression through development at 25 deg. C.