Heterozygotes are wild-type with pharyngeal GFP signal, and segregate WT GFP, arrested nT1[qIs51] aneuploids, and non-GFP csr-1(fj126) homozygotes (sterile, but some animals lay a small number of dead eggs). Homozygous nT1[qIs51] inviable. Pick WT GFP and check for correct segregation of progeny to maintain. fj126 was generated by the insertion of a synthetic nuclear export signal (NES). Instead of six amino-acid residues (R8–I13) near the N-terminus of CSR-1b, an NES sequence (LNELALKLAGLDI) from the cAMP-dependent protein kinase inhibitor alpha in mammals was inserted into the endogenous csr-1 gene. The DNA sequence encoding the NES has a HindIII site. The fj126 mutation can be checked by PCR with the following primers: AAGAAATACCAATGCGGAGGCA and CCGCTGAGGAACGAGATGG, followed by digestion with HindIII. Reference: Tabara H, et al. (2023) A small RNA system ensures accurate homologous pairing and unpaired silencing of meiotic chromosomes. EMBO J, e105002.