Abstract
Data presented in this paper test the hypotheses that Hirsch’s positive geotaxis (Lo) and negative geotaxis (Hi5) strains of Drosophila melanogaster (fruit fly) differ in length of the free-running circadian activity period (tau) as well as adult geotaxis.Several genes have been shown to alter geotaxis in Drosophila. Two of these genes, cryptochrome (cry) and Pigment-dispersing-factor (Pdf) are integral to the function of biological clocks. Pdf plays a crucial role in maintaining free-running circadian periods. The cry gene alters blue-light (<420 nm) phototransduction which affects biological clocks, spatial orientation and taxis relative to gravity, magnetic fields, solar, lunar, and celestial radiation in several species. The cry gene is involved in phase resetting (entrainment) of the circadian clock by blue light (<420 nm).Geotaxis involves spatial orientation, so it might be expected that geotaxis is linked genetically with other forms of spatial orientation. The association between geotaxis and biological clocks is less intuitive. The data and the literature presented here show that genes, physiology and behavioural aspects of geotaxis, biological clocks, magnetosensitivity and other types of spatial orientation, are complex, intriguing and interrelated.
Highlights
The strains of Drosophila melanogaster used in this study have been selected for positive and negative geotaxis since 1958 [1]
The data presented and the literature reviewed in this paper demonstrate that strains of D. melanogaster selected for divergent geotaxis differ in characteristics of their biological clocks
Methods & Results Results of statistical tests of difference between the sexes for circadian periods, and for geotaxis, were not significant (p>0.05), so data of the sexes were combined for analysis
Summary
The strains of Drosophila melanogaster used in this study have been selected for positive and negative geotaxis since 1958 [1] Hirsch and his students used r ecombination and chromosome substitution techniques to map multiple quantitative trait loci for geotaxis on each of the three large chromosomes (X, II, and III) of D. melanogaster [2,3]. They demonstrated that, in unselected (wild-type) D. melanogaster, genes on chromosomes X and II contributed mostly to positive geotaxis, and genes on chromosome III contributed to negative geotaxis [4]. Mutant alleles of the four genes exhibiting the most consistent mRNA differences between the geotaxis strains were transferred into wild-type
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