Sequence Differentiation Associated With an Inversion on the Neo-X Chromosome of Drosophila americana

Corresponding author: Bryant F. McAllister, 138 Biology Bldg., University of Iowa, Iowa City, IA 52242-1324., bryant-mcallister{at}uiowa.edu (E-mail)

Communicating editor: S. W. SCHAEFFER

Sex chromosomes originate from pairs of autosomes that acquire controlling genes in the sex-determining cascade. Universal mechanisms apparently influence the evolution of sex chromosomes, because this chromosomal pair is characteristically heteromorphic in a broad range of organisms. To examine the pattern of initial differentiation between sex chromosomes, sequence analyses were performed on a pair of newly formed sex chromosomes in Drosophila americana. This species has neo-sex chromosomes as a result of a centromeric fusion between the X chromosome and an autosome. Sequences were analyzed from the Alcohol dehydrogenase (Adh), big brain (bib), and timeless (tim) gene regions, which represent separate positions along this pair of neo-sex chromosomes. In the northwestern range of the species, the bib and Adh regions exhibit significant sequence differentiation for neo-X chromosomes relative to neo-Y chromosomes from the same geographic region and other chromosomal populations of D. americana. Furthermore, a nucleotide site defining a common haplotype in bib is shown to be associated with a paracentric inversion [In(4)ab] on the neo-X chromosome, and this inversion suppresses recombination between neo-X and neo-Y chromosomes. These observations are consistent with the inversion acting as a recombination modifier that suppresses exchange between these neo-sex chromosomes, as predicted by models of sex chromosome evolution.

This article has been cited by other articles:

				C. Lemaitre, M. D. V. Braga, C. Gautier, M.-F. Sagot, E. Tannier, and G. A. B. Marais Footprints of Inversions at Present and Past Pseudoautosomal Boundaries in Human Sex Chromosomes Gen Biol Evol, June 22, 2009; 2009(0): 56 - 66. [Abstract] [Full Text] [PDF]

				S. W. Schaeffer, A. Bhutkar, B. F. McAllister, M. Matsuda, L. M. Matzkin, P. M. O'Grady, C. Rohde, V. L. S. Valente, M. Aguade, W. W. Anderson, et al. Polytene Chromosomal Maps of 11 Drosophila Species: The Order of Genomic Scaffolds Inferred From Genetic and Physical Maps Genetics, July 1, 2008; 179(3): 1601 - 1655. [Abstract] [Full Text] [PDF]

				A. L. Evans, P. A. Mena, and B. F. McAllister Positive Selection Near an Inversion Breakpoint on the Neo-X Chromosome of Drosophila americana Genetics, November 1, 2007; 177(3): 1303 - 1319. [Abstract] [Full Text] [PDF]

				X. Maside and B. Charlesworth Patterns of Molecular Variation and Evolution in Drosophila americana and Its Relatives Genetics, August 1, 2007; 176(4): 2293 - 2305. [Abstract] [Full Text] [PDF]