Cytogenetic analysis of five species of the subfamily Corydoradinae (Teleostei: Siluriformes: Callichthyidae)

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

X monosomy and balanced Robertsonian translocation in a girl with Turner Syndrome

We describe a case of X monosomy associated with a maternally inherited t(13;14) Robertsonian translocation in a girl with Turner syndrome. The girl's X chromosome was demonstrated to be maternally inherited, ruling out the hypothesis that the translocation exerted an interchromosomal effect on the origin of the monosomy. Chromosomes 13 and 14 showed biparental inheritance.

Genotoxicity and mutagenicity of water contaminated with tannery effluents, as evaluated by the micronucleus test and comet assay using the fish Oreochromis niloticus and chromosome aberrations in onion root-tips

Cytotoxicity of metals is important because some metals are potential mutagens able to induce tumors in humans and experimental animals. Chromium can damage DNA in several ways, including DNA double strand breaks (DSBs) which generate chromosomal aberrations, micronucleus formation, sister chromatid exchange, formation of DNA adducts and alterations in DNA replication and transcription. In our study, water samples from three sites in the Córrego dos Bagres stream in the Franca municipality of the Brazilian state of São Paulo were subjected to the comet assay and micronucleus test using erythrocytes from the fish Oreochromis niloticus. Nuclear abnormalities of the erythrocytes included blebbed, notched and lobed nuclei, probably due to genotoxic chromium compounds. The greatest comet assay damage occurred with water from a chromium-containing tannery effluent discharge site, supporting the hypothesis that chromium residues can be genotoxic. The mutagenicity of the water samples was assessed using the onion root-tip cell assay, the most frequent chromosomal abnormalities observed being: c-metaphases, stick chromosome, chromosome breaks and losses, bridged anaphases, multipolar anaphases, and micronucleated and binucleated cells. Onion root-tip cell mutagenicity was highest for water samples containing the highest levels of chromium.

Nucleotide sequence, genomic organization and chromosome localization of 5S rDNA in two species of Curimatidae (Teleostei, Characiformes)

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

Cytogenetic divergence between two sympatric species of Characidium (Teleostei, Characiformes, Crenuchidae) from the Machado River, Minas Gerais, Brazil

Cytogenetic studies were performed on two sympatric species of Characidium, C. gomesi and C. cf. zebra, from the Grande River basin, Minas Gerais State, Brazil. Although both species had a chromosome number of 50 with a karyotype exclusively consisting of meta- and submetacentric chromosomes, interspecific diversity was detected concerning the size of the two first chromosome pairs of the karyotypes. Active nucleolus organizer regions (NORs) were located at the terminal position on the long arm of the 17th pair of C. gomesi and at subterminal position on the long arm of the 23rd pair of C. cf. zebra. For both species the fluorochrome CMA3 stained only the NOR-bearing pair of chromosomes. The heterochromatin pattern also showed some differentiation between these species restricted to the centromeric or pericentromeric region of C. cf. zebra and practically absent in C. gomesi. These data are discussed concerning chromosome diversification in this fish group.

Karyotype characterization, constitutive heterochromatin and nucleolus organizer regions of Paranaita opima (Coleoptera, Chrysomelidae, Alticinae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Evidence of an XX/XY sex chromosome system in the fish Dormitator maculatus (Teleostei, Eleotrididae)

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

Extensive polymorphism and chromosomal characteristics of ribosomal DNA in the characid fish Triportheus venezuelensis (Characiformes, Characidae)

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

Astylus variegatus (Coleoptera, Melyridae): Cytogenetic study of a population exposed to agrochemical products

In this work we describe the cytogenetic analyses performed in specimens of Astylus variegatus (Germar, 1824) collected in two localities: one area of natural vegetation and one of agricultural crops, where agrochemical products were used. Astylus variegatus had karyotypes with 2n(male) = 16+Xy p and 2n (female) = 16+XXp, with exclusively metacentric chromosomes. Pachytene spermatocytes showed synapsed autosomal bivalents and non-associated sex chromosomes. In diplotene, the autosomal bivalents exhibited one or two terminal chiasmata and the Xy p had a typical parachute configuration. In meiotic cells of some specimens, an extra chromosome, interpreted as a B chromosome, was observed. C-banding showed constitutive heterochromatin in the pericentromeric region of all chromosomes, with the exception of the y p. Silver nitrate staining revealed one nucleolus organizer region (NOR) on the terminal region of the short arm of the second autosome pair. Silver staining of meiotic cells confirmed the NOR pattern detected in mitotic cells and revealed an argentophilous material on the Xy p. A cytogenetic comparison between the two populations of A. variegatus showed a statistically significant divergence (chi2 = 117.10; df = 1) in the number of aneuploid cells and a higher frequency of B chromosome in the population exposed to agrochemicals.

Cytogenetic analysis of three sea catfish species (Teleostei, Siluriformes, Ariidae) with the first report of Ag-NOR in this fish family

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

Modelos alternativos para detecção de locos de características quantitativas (QTL) de carcaça e crescimento nos cromossomos 4, 5 e 7 de suínos

O conhecimento do genoma pode auxiliar na identificação de regiões cromossômicas e, eventualmente, de genes que controlam características quantitativas (QTLs) de importância econômica. em um experimento com 1.129 suínos resultantes do cruzamento entre machos da raça Meishan e fêmeas Large White e Landrace, foram analisadas as características gordura intramuscular (GIM), em %, e ganho dos 25 aos 90 kg de peso vivo (GP), em g/dia, em 298 animais F1 e 831 F2, e espessura de toucinho (ET), em mm, em 324 F1 e 805 F2. Os animais das gerações F1 e F2 foram tipificados com 29 marcadores microsatélites. Estudou-se a ligação entre os cromossomos 4, 6 e 7 com GIM, ET e GP. Análises de QTL utilizando-se metodologia Bayesiana foram aplicadas mediante três modelos genéticos: modelo poligênico infinitesimal (MPI); modelo poligênico finito (MPF), considerando-se três locos; e MPF combinado com MPI. O número de QTLs, suas respectivas posições nos três cromossomos e o efeito fenotípico foram estimados simultaneamente. Os sumários dos parâmetros estimados foram baseados nas distribuições marginais a posteriori, obtidas por meio do uso da Cadeia de Markov, algoritmos de Monte Carlo (MCMC). Foi possível evidenciar dois QTLs relacionados a GIM nos cromossomos 4 e 6 e dois a ET nos cromossomos 4 e 7. Somente quando se ajustou o MPI, foram observados QTLs no cromossomo 4 para ET e GIM. Não foi possível detectar QTLs para a característica GP com a aplicação dessa metodologia, o que pode ter resultado do uso de marcadores não informativos ou da ausência de QTLs segregando nos cromossomos 4, 6 e 7 desta população. Foi evidenciada a vantagem de se analisar dados experimentais ajustando diferentes modelos genéticos; essas análises ilustram a utilidade e ampla aplicabilidade do método Bayesiano.

Comparative cytogenetic and allozyme analysis of Mugil rubrioculus and M. curema (Teleostei : Mugilidae) from Venezuela

A comparative cytogenetic and allozyme analysis of sympatric specimens of Mugil rubrioculus and M. curema from Venezuela is reported. Specimens of M. rubrioculus exhibit a 2n=48 karyotype with exclusively acrocentric (NF=48) chromosomes, one pair of NORs interstitially located on chromosome pair number 8 and constitutive heterochromatin distributed in pericentromeric position of all chromosomes. Specimens of M. curema show cytogenetic features significantly different in comparison to M. rubrioculus in terms of chromosome number and morphology (2n=24 biarmed chromosomes, NF=48) and NORs location (telomeric region of the largest metacentric pair). Starch gel electrophoresis analysis at 20 presumptive loci reveals a reduced genetic difterentiation between the two species. In fact, though a total of ten private alleles are identified; all loci share alleles between the two species and the obtained Nei's genetic distance (D= 0.060) is lower than the values obtained between other congeneric mullet species. Thus, the cytogenetic and allozyme data sets indicate quite different degrees of genetic divergence between M. rubrioculus and M. curema. This could either reflect an underestimate of molecular divergence owing to cryptic variation or different rates of molecular/chromosomal evolution. Whatever the explanation, this study confirms the power of karyological data in discriminating species of Mugilidae.

NUCLEOLAR CHROMOSOME VARIANTS IN STERNOPYGUS-MACRURUS (PISCES, STERNOPYGIDAE) FROM 3 BRAZILIAN RIVER BASINS

The karyotypes, location of nucleolus organizer regions (NOR) and constitutive heterochromatin pattern of Sternopygus macrurus (Pisces, Gymnotoidei) of natural populations from the Amazon River, Sao Francisco River and Tiete River (the last belonging to the Upper Parana River system) are reported. All specimens had 2n = 46 chromosomes and presented small differences in karyotypic formulae, but populations of each river basin had a different fixed NOR phenotype. The loss of the satellite and a gradual deletion of the heterochromatin block adjacent to the NOR may be the origin of the variants. The possible mechanism of fixation of the NOR phenotypes, and the implications of the occurrence of intraspecific differences in fixed NOR phenotype in this species are discussed.

TELOMERIC FUSIONS IN A WILMS-TUMOR

The present report describes the karyotypic findings in cells from a Wilms' tumor. The most consistent cytogenetic abnormalities detected consisted of translocations involving break and fusion of chromosomal telomeres and telomeric associations frequently affecting the terminus of the short arms of chromosomes 14 and 17.

Chromosome banding in three species of Brazilian toads (Amphibia-Bufonidae)

The chromosomes of Bufo crucifer, B. ictericus, and B. pamacnemis were studied by conventional staining as well as with C banding and NOR techniques. These species have a diploid number of 2n = 22 and identical karyotypes, composed of metacentric and submetacentric chromosomes. The C banding patterns and NOR data indicate that these species of Bufo are not differentiated by the distribution and amount of constitutive heterochromatin or the position of the nucleolar organizer regions.