Genetic Analysis of Chromomere 3d4 in DROSOPHILA MELANOGASTER: The DUNCE and SPERM-AMOTILE Genes.

Both male and female Drosophila that are homozygous deficient for chromomere 3D4 are viable but sterile and lack detectable cAMP-specific phosphodiesterase activity. Two genes have been localized to this region: spermamotile (sam) and dunce (dnc). The sperm-amotile gene is required for male fertility, and the dunce gene is required for normal learning, female fertility, and cAMP-specific phosphodiesterase activity. The sperm-amotile gene maps 0.24 map units to the left of dunce. The expression of the dunce gene seems to be affected by a chromosomal break to the left of sperm-amotile. The fertility of dunce females varies according to changes in the genetic background and the presence or absence of an X-linked suppressor.