Homoeosis in Drosophila: Evidence for a maternal effect of the polycomb locus

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Abstract
When heterozygous, dominant mutant alleles of the Polycomb locus are associated with a variety of adult homoeotic effects. Zygotes homozygous for these alleles die as late embryos showing homoeotic transformation of head, thoracic, and abdominal segments. This study shows that embryos homozygous forPc3are more extreme than those homozygous forPc1orPc2. Moreover,Pc1/Pc3heterozygotes are more extensively transformed if their mothers werePc3/ + than if they werePc1/ +; this effect does not depend on zygotic genetic background and must be maternal in nature. Embryos homozygous forPc3are less extreme if they arise fromPc3/ + / + than fromPc3/ + mothers. These results strongly suggest that the Polycomb locus acts maternally as well as zygotically to affect early determinative decisions.