Isolation ofDrosophila melanogaster mutants with a wavelength-specific alteration in their phototactic response

A method is described for the isolation ofDrosophila mutants whose positive spontaneous phototactic reaction in repeated choices between UV light (368 nm) and blue light (481 nm) tended less to the UV than that of the wild type. From those 32 strains which have been isolated up till now and which fulfill this criterion, most showed only a relatively slight deviation from normal behavior. Among those exhibiting a marked change in the choice tendency was one allele of the mutantrdgB (receptor degeneration B) and seven alleles of the mutantsevenless (receptor cell 7 missing); four other mutants belong to two complementation groups which have not been identified as yet. The method described should be suitable for detecting further mutants with defects in receptor-cell function. In addition, it should be possible to isolate mutants in which the mechanisms of wavelength-specific processing are altered.