A nematode having null mutations in hop 1 and sel 12, said nematode having a combined maternal effect embryonic lethality and egg laying defective phenotype, at least one of said {HEAD ~ mutations} being introduced by {TAIL ~ artifice}, wherein said nematode is a C. elegans nematode 
introduced by
A nematode having null mutations in hop 1 and sel 12 , said nematode having a combined maternal effect embryonic lethality and egg laying defective phenotype , at least one of said { HEAD ~ mutations } being introduced by { TAIL ~ artifice } , wherein said nematode is a C. elegans nematode
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