part_of part of part of starts starts occurrent embryo stage part embryo stage life cycle life cycle stage zygote stage EMAPA:16033 XAO:1000001 BilaDO:0000005 ZFS:0000001 Wikipedia:Zygote one-cell stage UBERON:0000106 uberon EHDAA:27 VHOG:0000745 NCIT:C12601 zygote one cell stage A stage at which the organism is a single cell produced by means of sexual reproduction. fertilized egg stage zygotum 1-cell stage PdumDv:0000100 FBdv:00005288 EFO:0001322 IDOMAL:0000302 BILS:0000106 As in all metazoans, eumetazoan development begins with a fertilized egg, or zygote.[well established][VHOG] fertilized egg stage