Neurogenetics of courtship in drosophila : (courtship and mating, behavioral mutants, Drosophila gynandromorphs, visual and olfactory defects, circadian rhythms, learning and memory, neurotransmitter mutants)
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Courtship behavior in Drosophila is programmed by the action of genes that control the development and function of the nervous system. Several genes have been identified that appear to be involved in reproduction, because the mutations at these loci have specific defects in courtship. The mutations affect steps in the courtship pathway ranging from the early stage of wing vibration song to the final stage of copulation. Other single-gene mutants, not isolated on the basis of defective courtship, have been used to dissect further the behavioral pathway. All of these behavioral mutants exhibit particular defects in courtship, including expected abnormalities of general reproductive abilities in mutants that cannot see or smell, and more subtle changes caused by other mutations. The latter have revealed connections between courtship and biological oscillations or experience-dependent phenomena. These higher behavioral mutations are likely to affect the central nervous system. Other experiments on genetic variants affecting the central nervous system have involved gynandromorphs. From courtship tests of these mosaics, the presence of male tissue in a portion of the brain has been correlated with performance of the initial stages of courtship. If a gynandromorph is to exhibit later steps of courtship, such as normal song or attempted copulation, there must be male neurons in the thoracic nervous system as well as in the brain. Neural tissues of different sex-chromosome genotype have been identified in these mosaics, using enzyme mutations that mark internal cells. Some of these mutations, in addition, lead to specific neurochemical defects in the metabolism of the neurotransmitter acetylcholine. When such mutations are expressed in the mosaics, they not only mark tissues of different genotype, but they can also lead to specific defects in courtship behavior.