SUPPRESSION OF SEX-RATIO MEIOTIC DRIVE AND THE MAINTENANCE OF Y-CHROMOSOME POLYMORPHISM IN DROSOPHILA |
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Authors: | John Jaenike |
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Affiliation: | Department of Biology, University of Rochester, Rochester, New York, 14627 |
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Abstract: | Like several other species of Drosophila, D. quinaria is polymorphic for X-chromosome meiotic drive; matings involving males that carry a “sex-ratio” X chromosome (XSR) result in the production of strongly female-biased offspring sex ratios (Jaenike 1996). A survey of isofemale lines of D. quinaria from several populations reveals that there is genetic variation for partial suppression of this meiotic drive. Crossing experiments show that there is Y-linked, and probably autosomal, variation for suppression of drive. Y-linked suppressors of X-chromosome drive have now been described in several species of Diptera. I develop a simple model for the maintenance of Y-chromosome polymorphism in species polymorphic for X-linked meiotic drive. One interesting feature of this model is that, if there is a stable Y-chromosome polymorphism, then the equilibrium frequency of the standard and sex-ratio X chromosomes is determined solely by Y-chromosome parameters, not by the fitness effects of the different X chromosomes on their carriers. This model suggests that Y-chromosome polymorphism may be easier to maintain than previously thought, and I hypothesize that karyotypic variation in Y chromosomes will be found to be associated with suppression of sex-ratio meiotic drive in other species of Drosophila. |
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Keywords: | Drosophila quinaria genetic arms race population genetics segregation distortion selfish genes X-chromosome polymorphism Y-chromosome polymorphism |
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