Chromosome Location of Active Ribosomal Genes inPleurodema Thaul(Amphibia-Leptodactylidae). C-Banding and Polymorphism of The Nucleolar Organizer Region

Abstract

SUMMARYSpecimens of Pleurodema thaul collected in three localities from central Chile (32–33 SL), were studied. Patterns of C-heterochromatin distribution, localization and activity of Nucleolar Organizer Regions (NORs) were established using the silver banding technique and the fluorochrome quinacrine mustard. It was show that specimens from all localities have the same pattern of C-bands. In all except three specimens from one population there are only two NORs on chromosome pair number 8 in correspondence with two secondary constrictions present in Giemsa or quinacrine mustard stained chromosomes. In this three specimens, there is a supplementary secondary constriction in pair number 3, where there are active DNAr genes as is revealed by the silver chromosome stain and the number of nucleoli found in the interphase nuclei. Most specimens have differences in NORs length when carrier chromosomes are compared. However, there are no differences in nucleolar sizes in their interphase nuclei. The significance of NOR polymorphism and differences in length of this genome region are discussed.