Brains from mutant flies, when incubated with tritiated tyrosine, showed decreased dopamine and serotonin synthesis but normal octopamine synthesis. Mutant brains show undetectable Ddc and 5-HTdcprotein activity, but almost normal levels of Tdc product activity. Flies have normal circadian rhythms but fail to learn in either negatively or positively reinforced olfactory discrimination tests.

Restrictive temperatures are 29^oC and 30^oC. Permissive temperatures are 18^oC, 20^oC and 22^oC.

Homozygotes and hemizygotes show non-conditional, complete sterility. Although homozygous and hemizygous females do lay some eggs, no evidence of fertilization or embryogenesis has been detected. Ddc^ts1 heterozygotes with Ddc null alleles show temperature-dependent sterility.

Specific DDC activity of newly eclosed adult CyO/Ddc heterozygotes, as percentage of CyO/+ control: 65.5