Chrosomal banding in Parodon hilarii (Pisces Parodontidae), with emphassis on constitutive heterochromatin

摘要

Several banding methods were employed to analyze the chromosomes of the fish Parodon hilarii, i.e., C-banding, digestion with the restriction endonuclease Hae III, G-banding (trypsin), incorporation of 5-BrdU, and base-specific fluorochrome staining, with emphasis on the constitutive heterochromatin. The pattern obtained after the chromosomal cleavage with the restriction enzyme Hae III was similar to that of the C-banding. The incorporation of 5-bromodeoxiuridin (5-BrdU) in the chromosomes was able to detect several heterochromatin segments of late replication, with exception of some C-banded sites which were not evidenced after the 5-BrdU treatment. The terminal segment of the long arm of the 15 h chromosome pair, which corresponds to a NOR site, seems to be composed by AT-rich heterochromatic regions interspersed with CG-rich regions. Besides, the long arm of the W chromosome shows a structural differentiation concerning the distribution of the heterochromatin.