title: Molecular drift of the bride of sevenless (boss) gene in Drosophila.
abstract: DNA sequences were determined for three to five alleles of the bride-of-sevenless (boss) gene in each of four species of Drosophila. The product of boss is a transmembrane receptor for a ligand coded by the sevenless gene that triggers differentiation of the R7 photoreceptor cell in the compound eye. Population parameters affecting the rate and pattern of molecular evolution of boss were estimated from the multinomial configurations of nucleotide polymorphisms of synonymous codons. The time of divergence between D. melanogaster and D. simulans was estimated as approximately 1 Myr, that between D. teissieri and D. yakuba as approximately 0.75 Myr, and that between the two pairs of sibling species as approximately 2 Myr. (The boss genes themselves have estimated divergence times approximately 50% greater than the species divergence times.) The effective size of the species was estimated as approximately 5 x 10(6), and the average mutation rate was estimated as 1-2 x 10(-9)/nucleotide/generation. The ratio of amino acid polymorphisms within species to fixed differences between species suggests that approximately 25% of all possible single-step amino acid replacements in the boss gene product may be selectively neutral or nearly neutral. The data also imply that random genetic drift has been responsible for virtually all of the observed differences in the portion of the boss gene analyzed among the four species.
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138.
authors.forename: F J
authors.initials: FJ
authors.lastname: Ayala
authors.forename: D L
authors.initials: DL
authors.lastname: Hartl
mesh_terms: D000426:Alcohol Dehydrogenase / Q000235:genetics; D000483:Alleles; D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000235:genetics; D004330:Drosophila / Q000145:classification / Q000235:genetics*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics; D005136:Eye Proteins / Q000235:genetics*; D005787:Gene Frequency; D017344:Genes, Insect; D008562:Membrane Glycoproteins / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D018000:Receptors, Peptide; D012641:Selection, Genetic; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
chemical_list: D029721:Drosophila Proteins; D005136:Eye Proteins; D008562:Membrane Glycoproteins; D018000:Receptors, Peptide; C072141:boss protein, Drosophila; D004247:DNA; D000426:Alcohol Dehydrogenase