title: Chromosome banding in Amphibia. VI. BrdU-replication patterns in anura and demonstration of XX/XY sex chromosomes in Rana esculenta.
abstract: A modified BrdU-Hoechst-Giemsa technique permitted the demonstration of easily reproducible replication patterns in the somatic chromosomes of Amphibia. These banding patterns allow for the first time a precise identification of all chromosomes and the analysis of the patterns of replication in the various stages of S-phase in Amphibia. Several possibilities for the use of this technique were demonstrated on three frog species of the family Ranidae, all differing greatly in their DNA-content. With this method, the homomorphic chromosome pair No. 4 in Rana esculenta could be identified as sex-specific chromosomes of the XX/XY-type. All male animals exhibit an extremely late replicating region in the Y-chromosome, which is lacking in the X-chromosome in the female animals, both X-chromosomes replicate synchronously. These sex-specific chromosomes cannot be distinguished by other banding techniques. In the highly heteromorphic ZZ/ZW-sex chromosome system of Pyxicephalus adspersus a synchronous replication of the two Z-chromosomes of male animals and a very late replication of the short arm of the W-chromosomes of male animals was demonstrated. These results support the assumption that there is no dosage compensation for Z-linked or X-linked genes by the sex chromosome inactivation mechanism in the sex chromosomes of Amphibia.
mesh_terms: D000818:Animals; D001001:Anura / Q000235:genetics*; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002871:Chromosome Banding / Q000379:methods*; D002875:Chromosomes / Q000648:ultrastructure*; D004261:DNA Replication / Q000187:drug effects; D004303:Dosage Compensation, Genetic; D005260:Female; D007621:Karyotyping; D008297:Male; D011893:Rana esculenta / Q000235:genetics; D011896:Rana temporaria / Q000235:genetics; D012730:Sex Chromosomes / Q000648:ultrastructure*
chemical_list: D001973:Bromodeoxyuridine