Molecular characterization of the Drosophila vermilion locus and its suppressible alleles.

We have cloned vermilion (v), one of the genes required for brown eye pigment synthesis in Drosophila, using a mutant (vH2a) "tagged" with the transposon P factor. Mutations that disrupt v gene expression are clustered within approximately 2 kilobases of DNA. A 1.4-kilobase transcript, homologous to this same region, is present in v+ RNA but absent in RNA from several v mutants. The spontaneous v alleles that are suppressed by the suppressor of sable [su(s)] are apparently identical insertions of 412, a copia-like transposable element. Preliminary evidence suggests that su(s)-suppressible alleles at other loci may also be 412 insertions.