Maternal-Zygotic Lethal Interactions in DROSOPHILA MELANOGASTER : Zeste-White Region Single-Cistron Mutations.

Thirty-eight mutations in 13 essential loci in the zeste-white region were tested for interacting maternal and zygotic gene activity. Maternal mutant heterozygosity provided a partial maternal defect and position-effect variegation was used to alter the level of zygotic gene activity. This method yields a minimum estimate of the number of genes for which zygotic development depends upon both gene products stored in the egg and gene products synthesized in the zygote. Lethal interactions were found for one or more alleles at 10 of the 13 loci. The implications of these observations with respect to gene regulation and developmental sequence are considered.