Trans-acting amplification mutants and other eggshell mutants of the third chromosome in Drosophila melanogaster.

We report on the characterization of five third chromosome mutations with strong effects on the formation of the eggshell or chorion. Three mutations, defining two loci, result in substantially reduced follicle cell-specific amplification of the major chorion structural genes and, hence, in underproduction of the corresponding mRNAs and proteins. The other two mutations, though displaying structural chorion abnormalities, appear to have no significant effect on amplification and to express normally the major chorion structural genes. The possible nature of these mutations is discussed.