title: Global patterns of sequence evolution in Drosophila.
abstract: BACKGROUND
  Sequencing of the genomes of several Drosophila allows for the first precise analyses of how global sequence patterns change among multiple, closely related animal species. A basic question is whether there are characteristic features that differentiate chromosomes within a species or between different species.
  
  
  RESULTS
  We explored the euchromatin of the chromosomes of seven Drosophila species to establish their global patterns of DNA sequence diversity. Between species, differences in the types and amounts of simple sequence repeats were found. Within each species, the autosomes have almost identical oligonucleotide profiles. However, X chromosomes and autosomes have, in all species, a qualitatively different composition. The X chromosomes are less complex than the autosomes, containing both a higher amount of simple DNA sequences and, in several cases, chromosome-specific repetitive sequences. Moreover, we show that the right arm of the X chromosome of Drosophila pseudoobscura, which evolved from an autosome 10 - 18 millions of years ago, has a composition which is identical to that of the original, left arm of the X chromosome.
  
  
  CONCLUSIONS
  The consistent differences among species, differences among X chromosomes and autosomes and the convergent evolution of X and neo-X chromosomes demonstrate that strong forces are acting on drosophilid genomes to generate peculiar chromosomal landscapes. We discuss the relationships of the patterns observed with differential recombination and mutation rates and with the process of dosage compensation.
authors.affiliation: Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Científicas (IBV-CSIC), Valencia, Spain. miguel.gallach@uv.es
authors.forename: Miguel
authors.initials: M
authors.lastname: Gallach
authors.forename: Vicente
authors.initials: V
authors.lastname: Arnau
authors.forename: Ignacio
authors.initials: I
authors.lastname: Marín
mesh_terms: D000818:Animals; D001483:Base Sequence; D004247:DNA; D004330:Drosophila / Q000235:genetics*; D019143:Evolution, Molecular; D020869:Gene Expression Profiling; D013045:Species Specificity; D014960:X Chromosome
chemical_list: D004247:DNA