Molecular analysis of no-on-transient A, a gene required for normal vision in Drosophila.

Mutation of the Drosophila melanogaster gene no-on-transient A (nonA) results in reduced visual acuity, behavior abnormalities, and an electrophysiological defect for which the mutant is named. We mapped the nonA gene genetically to a 20 kb interval within the 14C1,2 region of the X chromosome, isolated this chromosomal region, and used P element-mediated transformation to delimit the nonA gene to a 9 kb region. Analysis of cDNA clones indicates that this region encodes alternatively spliced transcripts encoding protein products of approximately 77 kd that differ only in their C-terminal 35 amino acids. Analysis of mutations generated in vitro in this transcription unit confirm that these transcripts are the products of the nonA gene.