We have utilized a screen for maternal effect lethal mutations ( Preiss, J., Kemphues, K., Wolf, N., and Hirsh, D. (1984) WBG 8(2),5) to search for mutations that may be due to Tc1 transposition. The egg- laying defective mutation,
egl-23 (
n601) IV, was crossed into strains bearing the mutators
mut-2 (
r459) or
mut-3 (
r456) (Phil Anderson, Bonnie Saari, and John Collins (1985) WBG 9(1), 29). New maternal effect mutations that arose during propagation were identified as heterozygotes: 1/4 of their progeny produced dead eggs and were not consumed by larva (they did not 'bag'). In our preliminary screens, we picked 1500
egl-23; and 600
egl-23;
mut-3 worms. We identified three maternal effect mutations in the
mut-2 background:
jb2,
jb3, and
jb7. Homozygous
jb2 hermaphrodites will produce a few progeny (~1-10) inevitably sterile. Early divisions of eggs from which are
jb2 hermaphrodites are symmetric and synchronous, reminiscent of mutations in the par loci. Indeed,
jb2 fails to complement
par-2 (
it5) III (Niansheng Cheng, Diane Morton, and Ken Kemphues, this issue). Hermaphrodites homozygous for the mutation
jb3 (which maps to chromosome III) produce eggs with variable terminal phenotypes; no clear defect in early divisions can be seen. Strains homozygous for the
jb7 mutation produce eggs whose early divisions are far slower than wild type. We've isolated one maternal effect mutation from the
mut-3 background,
jb6. The
jb6 mutants produce eggs whose first observable defects are in gastrulation and/or the timing of the second round of division of the E lineage. Genetic and molecular analysis of these maternal effect alleles and screens to identify additional mutations are in progress.