Deletion mapping of the Drosophila memory mutant amnesiac.

Guided by genetic recombination experiments that placed the gene for the Drosophila memory mutant amnesiac proximal to forked near carnation, we screened 7 deficiencies of the proximal X in an effort to more precisely localize the amnesiac mutation. After training with a classical conditioning procedure, two deficiency chromosomes, mal8 and mal12, produced amnesiac-like memory deficits in Df/amn flies but not in Df/ + controls. In contrast, the mal13, mal10, mal11, 16-3-22 and DCB1 deficiencies, in combination with either amn or + chromosomes, did not produce amnesiac memory scores. These results indicate that the amnesiac gene lies between the left breakpoint of mal12 (19A1) and the left breakpoint of mal13 (19A1 or A2). This conclusion is supported by the fact that amn males carrying the Y-linked X-chromosome duplication y+ Ymal106 (which spans 18F4-5 to 20A) produce wild-type learning and memory scores. Finally, the data suggest that amnesiac is a complete loss of function (amorphic) mutation, because amn/amn and amn/Df flies have similar learning and memory scores.