THE MOLECULAR-ORGANIZATION OF THE STAR ASTEROID REGION, A REGION NECESSARY FOR PROPER EYE DEVELOPMENT IN DROSOPHILA-MELANOGASTER/

The Star/asteroid (S/ast) region of Drosophila melanogast has been clo ned by P element transposon tagging using the sn(w) chromosome as a so urce of defective P elements. In each mutation examined, the element i ntegrated into the region was a 0.5-kb element from a region proximal to sn and not one of the head-to-head elements from the sn locus. Prev iously described spontaneous and X-ray induced mutations of S and ast were located on the molecular map by Southern analysis and restriction endonuclease mapping of genomic clones. S mutations are either large deletions of the cloned region or DNA -breaks located near the P eleme nt insertions that cause ast mutations. Both S and ast mutations reduc e the steady-state amounts of a 3.4-kb RNA. The molecular data, togeth er with the phenotypic interactions observed for S and ast alleles, ar e consistent with the interpretation that S and ast mutations are lesi ons within the same gene or within genes that are functionally related .