title: Chromosome mapping of Xenopus tropicalis using the G- and Ag-bands: tandem duplication and polyploidization of larvae heads.
abstract: Developmental cytogenetic analyses of Xenopus tropicalis larvae from two origins were performed on stage 27-34 heads treated with colchicine. Standard G-band karyotyping using trypsin and chromosome mapping of 184 bands were examined. Although the main karyotype was 2n = 20, polyploidy (3n = 30 or 4n = 40) and aneuploidy were detected in each individual treated with colchicine, even those treated for only 1 h. The percentage of polyploid karyotypes was 10-20% across the total of measured metaphases. The mean mitotic index was 0.10. Chromosomal breaks and exchanges were detected at the secondary constriction of chromosomes 5 or 6. Ag-band detection showed clearly positive staining at the secondary constriction of chromosome 5, which corresponds to the nucleolar organizer region. Tandem duplication of negative G-bands at the secondary constriction of chromosome 6 and the short arm of chromosome 10 was suggested by this study. X. tropicalis thus provides a good model to study the mechanism and effects of chromosomal abnormalities, gene mapping and tissue specific gene expression in the developmental process.
authors.affiliation: Department of Life Science, Teikyo Junior College, 6-31-1 Honmachi, Shibuya-ku, Tokyo 151-0071, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Uehara
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Haramoto
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Sekizaki
authors.forename: Shuji
authors.initials: S
authors.lastname: Takahashi
authors.forename: Makoto
authors.initials: M
authors.lastname: Asashima
mesh_terms: D000818:Animals; D002871:Chromosome Banding; D002874:Chromosome Mapping; D005260:Female; D020440:Gene Duplication; D006257:Head; D007621:Karyotyping; D007814:Larva / Q000235:genetics; D008297:Male; D011123:Polyploidy; D014981:Xenopus / Q000235:genetics*