title: Analysis of repetitive DNA sequences in the sex chromosomes of Oreochromis niloticus.
abstract: In the Nile tilapia, Oreochromis niloticus, sex determination is primarily genetic, with XX females and XY males. While the X and Y chromosomes (the largest pair) cannot be distinguished in mitotic chromosome spreads, analysis of comparative hybridization of X and Y chromosome derived probes (produced, by microdissection and DOP-PCR, from XX and YY genotypes, respectively) to different genotypes (XX, XY and YY) has demonstrated that sequence differences exist between the sex chromosomes. Here we report the characterization of these probes, showing that a significant proportion of the amplified sequences represent various transposable elements. We further demonstrate that concentrations of a number of these individual elements are found on the sex chromosomes and that the distribution of two such elements differs between the X and Y chromosomes. These findings are discussed in relation to sex chromosome differentiation in O. niloticus and to the changes expected during the early stages of sex chromosome evolution.
authors.affiliation: Institute of Aquaculture, University of Stirling, Stirling, UK.
authors.forename: S C
authors.initials: SC
authors.lastname: Harvey
authors.forename: C
authors.initials: C
authors.lastname: Boonphakdee
authors.forename: R
authors.initials: R
authors.lastname: Campos-Ramos
authors.forename: M T
authors.initials: MT
authors.lastname: Ezaz
authors.forename: D K
authors.initials: DK
authors.lastname: Griffin
authors.forename: N R
authors.initials: NR
authors.lastname: Bromage
authors.forename: P
authors.initials: P
authors.lastname: Penman
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D020223:Chromosome Painting; D023681:Cichlids / Q000235:genetics*; D004251:DNA Transposable Elements; D019143:Evolution, Molecular; D005260:Female; D008297:Male; D008957:Models, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D017422:Sequence Analysis, DNA; D012730:Sex Chromosomes / Q000737:chemistry*
chemical_list: D004251:DNA Transposable Elements