Chromosomal karyotypes of Oreochromis mossambicus and O. urolepis hornorum and their hybrid were analysed by means of Cot-1 DNA bandings through fluorescence in situ hybridization (FISH). To identify all chromosomes, Cot-1DNA - which contains highly and moderately repetitive DNA - was extracted from genomic DNA, labelled as a probe with Dig-11-dUTP, and in situ hybridized to spreads of mitotic chromosomes of the three samples. The hybridized signals were detected by means of Cy3-conjugated antidigoxigenin. The FISH results indicated that the three samples had the same diploid number (2n = 44) of chromosomes. Specific fluorescence signal bands were detected on all individual chromosome pairs. On the basis of Cot-1 DNA FISH banding patterns and chromosome morphology, the karyotypes of the three samples have been constructed; no remarkable differences were detected between the karyotypes of these species using this method. These results - which are similar to those reported previously, with respect to chromosome number, morphology and Cot-1DNA FISH patterns - suggest chromosomal stasis during speciation and hybridization of tilapia (Oreochromis, Cichlidae). Such a molecular cytogenetic procedure, if used in conjunction with other genomic research methods, could facilitate the study of genomic structure and be adapted for chromosome studies of other animal species.
Zhu, Hua Ping; Lu, Mai Xin; Huang, Zhang Han; Gao, Feng Ying; Ma, Dong Mei; Zhou, Li; Gui, Jian Fang.Karyotype analysis of Oreochromis mossambicus, O. urolepis hornorum and their hybrid based on Cot-1 DNA bands by fluorescence in situ hybridization,AQUACULTURE RESEARCH,2011,42(8):1178-1185