Development of Y-chromosome-Specific SCAR Markers Conserved in Taurine, Zebu and Bubaline Cattle

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural and functional evidence that a B chromosome in the characid fish Astyanax scabripinnis is an isochromosome

Astyanax scabripinnis possesses a widespread polymorphism for metacentric B chromosomes as large as the largest chromosome pair in the A complement. on the basis of C-banding pattern, it was hypothesized that these B chromosomes are isochromosomes that have arisen by means of centromere misdivision and chromatid nondisjunction. In the present paper we test this hypothesis by analysing (i) the localization of a repetitive DNA sequence on both B chromosome arms, and (ii) synaptonemal complex formation, in order to test the functional homology of both arms. Genomic DNA digested with KpnI and analysed by gel electrophoresis showed fragments in a ladder-like pattern typical of tandemly repetitive DNA. These fragments were cloned and their tandem organization in the genome was confirmed. A 51-bp long consensus sequence, which was AT-rich (59%) and contained a variable region and two imperfect reverse sequences, was obtained. Fluorescence in situ hybridization (FISH) localized this repetitive DNA into noncentromeric constitutive heterochromatin which encompasses the terminal region of some acrocentric chromosomes, the NOR region, and interstitial polymorphic heterochromatin in chromosome 24. Most remarkably, tandem repeats were almost symmetrically placed in the two arms of the B chromosome, with the exception of two additional small clusters proximally located on the slightly longer arm. Synaptonemal complex (SC) analysis showed 26 completely paired SCs in males with 1B. The ring configuration of the B univalent persisting until metaphase I suggests that the two arms formed chiasmata. All these data provided strong support for the hypothesis that the B chromosome is an isochromosome.

Genomic content and new insights on the origin of the B chromosome of the cichlid fish Astatotilapia latifasciata

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Physical chromosome mapping of repetitive DNA sequences in Nile tilapia Oreochromis niloticus: Evidences for a differential distribution of repetitive elements in the sex chromosomes

Repetitive DNAs have been extensively applied as physical chromosome markers on comparative studies, identification of chromosome rearrangements and sex chromosomes, chromosome evolution analysis, and applied genetics. Here we report the characterization of repetitive DNA sequences from the Nile tilapia (Oreochromis niloticus) genome by construction and screening of plasmid library enriched with repetitive DNAs, analysis of a BAC-based physical map, and hybridization to chromosomes. The physical mapping of BACs enriched with repetitive sequences and C(o)t-1 DNA (DNA enriched for highly and moderately repetitive DNA sequences) to chromosomes using FISH showed a predominant distribution of repetitive elements in the centromeric and telomeric regions and along the entire length of the largest chromosome pair (X and Y sex chromosomes) of the species. The distribution of repetitive DNAs differed significantly between the p arm of X and Y chromosomes. These findings suggest that repetitive DNAs have had an important role in the differentiation of sex chromosomes. (c) 2007 Elsevier Ltd. All rights reserved.

Comparative chromosome mapping of repetitive sequences. Implications for genomic evolution in the fish, Hoplias malabaricus

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Supernumerary chromosome inheritance in the curimbata (Prochilodus lineatus) of the Mogi-Guacu River

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chromosome spreading of associated transposable elements and ribosomal DNA in the fish Erythrinus erythrinus. Implications for genome change and karyoevolution in fish

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cytogenetic mapping of the W chromosome in the genus Leporinus (Teleostei, Anostomidae) using a highly repetitive DNA sequence

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Extreme degree of chromosome number variability in species of the spider genus Scytodes (Araneae, Haplogynae, Scytodidae)

Genus Scytodes includes most species of the spider family Scytodidae. Until now, 187 species of the genus have been described. In spite of this great diversity, only three Scytodes species were karyotyped so far. The present paper provides for the first time karyotype analysis of two synanthropic species, Scytodes fusca and Scytodes itapevi. Furthermore, new data on karyotype of Scytodes globula are also provided using conventional and differential cytogenetical procedures. The diploid number in the genus Scytodes varied considerably, namely from 2n = 13 to 2n = 31. The diploid number found in S. globula (2n male = 13) is the lowest in haplogyne spiders with monocentric chromosomes. Except S. globula, this number has been found only in one haplogyne spider with monocentric chromosomes, namely Ochyrocera sp. (Ochyroceratidae). on the contrary, the diploid number of S. fusca (2n male = 31) is one of the highest diploid numbers recorded in haplogyne spiders. The degree of intrageneric variation found in the genus Scytodes is the highest recorded in araneomorph spiders with monocentric chromosomes so far. Some karyotype characteristics (diploid number, chromosome morphology, total chromosome length, and distribution of constitutive heterochromatin) allowed us to postulate a close relationship between S. globula and S. itapevi. According to the karyotype data, S. fusca is not closely related to these two species. This conclusion corroborates a recent taxonomic work that grouped S. globula, S. itapevi, and other four Scytodes species in the 'globula group'.

Chromosome evolution in three Brazilian Leptodactylus species (Anura, Leptodactylidae), with phylogenetic considerations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Preliminary radiation hybrid map for river buffalo chromosome 6 and comparison to bovine chromosome 3

We present the first radiation hybrid (RH) map of river buffalo (Bubalus bubalis) chromosome 6 (BBU6) developed with a recently constructed river buffalo whole-genome RH panel (BBURH5000). The preliminary map contains 33 cattle-derived markers, including 12 microsatellites, 19 coding genes and two ESTs, distributed across two linkage groups. Retention frequencies for markers ranged from 14.4% to 40.0%. Most of the marker orders within the linkage groups on BBU6 were consistent with the cattle genome sequence and RH maps. This preliminary RH map is the starting point for comparing gene order between river buffalo and cattle, presenting an opportunity for the examination of micro-rearrangements of these chromosomes. Also, resources for positional candidate cloning in river buffalo are enhanced.