Delimiting the Origin of a B Chromosome by FISH Mapping,Chromosome Painting and DNA Sequence Analysis in Astyanax paranae (Teleostei,Characiformes) |
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Authors: | Duílio M. Z. de A. Silva José Carlos Pansonato-Alves Ricardo Utsunomia Cristian Araya-Jaime Francisco J. Ruiz-Ruano Sandro Natal Daniel Diogo Teruo Hashimoto Cláudio Oliveira Juan Pedro M. Camacho Fábio Porto-Foresti Fausto Foresti |
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Abstract: | Supernumerary (B) chromosomes have been shown to contain a wide variety of repetitive sequences. For this reason, fluorescent in situ hybridisation (FISH) is a useful tool for ascertaining the origin of these genomic elements, especially when combined with painting from microdissected B chromosomes. In order to investigate the origin of B chromosomes in the fish species Astyanax paranae, these two approaches were used along with PCR amplification of specific DNA sequences obtained from the B chromosomes and its comparison with those residing in the A chromosomes. Remarkably, chromosome painting with the one-arm metacentric B chromosome probe showed hybridization signals on entire B chromosome, while FISH mapping revealed the presence of H1 histone and 18S rDNA genes symmetrically placed in both arms of the B chromosome. These results support the hypothesis that the B chromosome of A. paranae is an isochromosome. Additionally, the chromosome pairs Nos. 2 or 23 are considered the possible B chromosome ancestors since both contain syntenic H1 and 18S rRNA sequences. The analysis of DNA sequence fragments of the histone and rRNA genes obtained from the microdissected B chromosomes showed high similarity with those obtained from 0B individuals, which supports the intraspecific origin of B chromosomes in A. paranae. Finally, the population hereby analysed showed a female-biased B chromosome presence suggesting that B chromosomes in this species could influence sex determinism. |
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