Nucleolus organizer regions in the chromosomes of river, swamp and crossbred buffaloes [Malaysia]
1983
Hilmi, M. | Bongso, T.A. (Universiti Pertanian Malaysia, Serdang, Selangor (Malaysia). Faculty of Veterinary Medicine and Animal Science)
The chromosome number in the Murrah buffalo was shown to be 2N = 50 (Fisher and Ulbuch, 1968) and the swamp type of most Asian countries including Malaysia, 2N = 48 (Ulbrich and Fisher, 1967). The F1 hybrid between Murrah and swamp was shown to have a 2N = 49 complement intermediate to the two parental types (Bongso land Jainudon, 1979). Studies on G, C and conventional karyotypes revealed that the largest two metacentric chromosomes in the swamp buffaloes probably resulted from a telomere-centromere tandem fusion between chromosomes pairs 4p and 9 of the Murrah karyotype. Silver stained Nucleolus Organizer Regions (NOR) in this study have been observed in the telomeric regions of 3p, 4p, 8, 21, 23 and 24 of the Murrah karyotype and 3p, 8, 21, 23 and 24 of the swamp karyotype. The absence of the NOR's in the telomeric regions and chromatids1466(p) of the large metacentric chromosome pairs situated at group 4 of the Swamp karyotype suggests that breaks occurred at the telometric regions of chromosomes pairs 4p of the Murrah and the broken ends united with another acrocentric chromosomes not carrying NOR. This may have occurred via tandem fusion, where a break in the vicinity of the centromere of the acrocentric chromosomes resulted in a transfer of both arms of this chromosomes to the broken telomeric ends of 4p. The fact that in the Murrah, Swamp and their crosses, the NOR's are located on similar chromosomes suggests conservation of number and location of NOR's in this species during its evolution. Similar NOR conservation has been reported in the evolution of the sheep, goat, cattle and aoudad (Henderson and Bruere, 1979). The number of nucleoli in interphase nuclei (Murrah = 6; Swamp = 5, F1 hybrid = 5 large, 1 small), corresponded to the number of NOR pai
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