maIs103[rnr::GFP unc-36(+)] X. Heterozygotes produce 1/4 thin, sterile, uncoordinated animals that fail to undergo postembryonic somatic cell divisions. rnr::GFP is expressed during S-phase in heterozygous animals. rnr::GFP expression is not detected in heDf1 animals. Although the map position of maIs103 has not been determined conclusively, maIs103 genetically behaves linked to cdk-4. Maintain by picking several single animals and scoring for 1/4 mutant progeny.