title: Molecular population genetics of Xdh and the evolution of base composition in Drosophila.
abstract: Few loci have been measured for DNA polymorphism and divergence in several species. Here we report such data from the protein-coding region of xanthine dehydrogenase (Xdh) in 22 species of Drosophila. Many of our samples were from closely related species, allowing us to confidently assign substitutions to individual lineages. Surprisingly, Xdh appears to be fixing more A/T mutations than G/C mutations in most lineages, leading to evolution of higher A/T content in the recent past. We found no compelling evidence for selection on protein variation, though some aspects of the data support the notion that a significant fraction of amino acid polymorphisms are slightly deleterious. Finally, we found no convincing evidence that levels of silent heterozygosity are associated with rates of protein evolution.
authors.affiliation: Section of Integrative Biology, University of Texas, Austin, Texas 78712, USA. djbegun@ucdavis.edu
authors.forename: David J
authors.initials: DJ
authors.lastname: Begun
authors.forename: Penn
authors.initials: P
authors.lastname: Whitley
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001482:Base Composition; D004247:DNA / Q000737:chemistry* / Q000235:genetics*; D004330:Drosophila / Q000196:embryology* / Q000235:genetics*; D019143:Evolution, Molecular; D017344:Genes, Insect; D014644:Genetic Variation; D005828:Genetics, Population; D006579:Heterozygote; D008967:Molecular Biology; D008969:Molecular Sequence Data; D009154:Mutation; D011110:Polymorphism, Genetic; D012641:Selection, Genetic; D013045:Species Specificity; D014968:Xanthine Dehydrogenase / Q000235:genetics*
chemical_list: D004247:DNA; D014968:Xanthine Dehydrogenase