title: B chromosome in the beetle Coprophanaeus cyanescens (Scarabaeidae): emphasis in the organization of repetitive DNA sequences.
abstract: BACKGROUND
  To contribute to the knowledge of coleopteran cytogenetics, especially with respect to the genomic content of B chromosomes, we analyzed the composition and organization of repetitive DNA sequences in the Coprophanaeus cyanescens karyotype. We used conventional staining and the application of fluorescence in situ hybridization (FISH) mapping using as probes C0t-1 DNA fraction, the 18S and 5S rRNA genes, and the LOA-like non-LTR transposable element (TE).
  
  
  RESULTS
  The conventional analysis detected 3 individuals (among 50 analyzed) carrying one small metacentric and mitotically unstable B chromosome. The FISH analysis revealed a pericentromeric block of C0t-1 DNA in the B chromosome but no 18S or 5S rDNA clusters in this extra element. Using the LOA-like TE probe, the FISH analysis revealed large pericentromeric blocks in eight autosomal bivalents and in the B chromosome, and a pericentromeric block extending to the short arm in one autosomal pair. No positive hybridization signal was observed for the LOA-like element in the sex chromosomes.
  
  
  CONCLUSIONS
  The results indicate that the origin of the B chromosome is associated with the autosomal elements, as demonstrated by the hybridization with C0t-1 DNA and the LOA-like TE. The present study is the first report on the cytogenetic mapping of a TE in coleopteran chromosomes. These TEs could have been involved in the origin and evolution of the B chromosome in C. cyanescens.
authors.affiliation: Department of Morphology, Bioscience Institute, UNESP - Sao Paulo State University, Botucatu, SP, 18618-970, Brazil.
authors.forename: Sarah
authors.initials: S
authors.lastname: Gomes de Oliveira
authors.forename: Rita
authors.initials: R
authors.lastname: Cassia de Moura
authors.forename: Cesar
authors.initials: C
authors.lastname: Martins
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D002875:Chromosomes / Q000235:genetics*; D001517:Coleoptera / Q000235:genetics*; D004251:DNA Transposable Elements / Q000235:genetics; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008677:Metaphase; D005810:Multigene Family; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012341:RNA, Ribosomal, 5S / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*
chemical_list: D004251:DNA Transposable Elements; D012337:RNA, Ribosomal, 18S; D012341:RNA, Ribosomal, 5S