[The Delta locus in Drosophila virilis: alleles, wing phenotypes and genetic interactions].

A considerable number of Delta (D1) alleles resulting from spontaneous mutation or induced by following X-ray irradiation have been isolated on the basis of the dominant phenotype consisting of disrupted wing venation and associated with heterozygosity for different D1 alleles. The L2 "delta" forming at the wing margin is the most characteristic fully penetrant phenotype of D1-heterozygous adults. The structure disruption of all other longitudinal (L3-L5) and cross (C1 and C2) veins including formation of "deltas" and other additional vein material, have been characterized as the irregular bilaterally asymmetrical nondirectional fluctuations of D1 phenotype expression. The phenotypic interactions between Delta and two D1 phenotype enhancer mutations, L2 fork and gap L2, have been found. Possible participation of Delta, one of the elements of Notch signaling system, in the structure formation is discussed.