Mutants suppressing in trans chorion gene amplification in Drosophila.

Two recessive female-sterile mutants, K451 and K1214 , disrupt chorion formation by causing underproduction of all major chorion proteins. We present evidence that this effect is due to underaccumulation of the chorion mRNAs and that, in turn, this is caused by a substantial reduction in the level of chorion gene amplification. The mutants are X-linked but located at two sites far from the chorion gene cluster at 7F1 -2; their effect is even more pronounced on the third chromosome chorion gene cluster, and thus the wild type gene must act in trans. The time course of amplification in mutant and wild-type follicles is documented.