Maternal effects of general and regional specificity on embryos of Drosophila melanogaster caused by dunce and rutabaga mutant combinations.

The developmental patterns of embryos produced by female germ line cells homozygous for null-enzyme mutations of dunce and for dunce in combination with each of three different rutabaga mutations are compared with the normal pattern. At least three discrete developmental defects at progressive stages following fertilization can be identified and correlated with the loss of adenylate cyclase activity caused by rutabaga mutations, suggesting that the defects are caused by elevated cyclic AMP levels in female germ line cells. The earliest defect occurs soon after fertilization and affects DNA replication and mitosis, prevents nuclear migration, and leads to large polyploid nuclei. A later defect prevents cleavage nuclei from migrating into, or dividing in, the posterior region of the egg. The last affects the developmental behavior or fate of blastoderm cells. Some of these defects mimic those produced by previously described maternal-effect mutations.