Chromosomal analysis of the leptodactylids Pleurodema diplolistris and Physalaemus nattereri (Amphibia, Anura)

2006 ◽  
Vol 27 (4) ◽  
pp. 481-489 ◽  
Author(s):  
Luciana B. Lourenço ◽  
Josiane A.A. Nascimento ◽  
Gilda V. Andrade ◽  
Denise C. Rossa-Feres ◽  
Shirlei M. Recco-Pimentel
Keyword(s):  
Nucleolar Organizer ◽  
The Other ◽  
Chromosomal Analysis ◽  
Nucleolar Organizer Regions ◽  
Chromosome 11 ◽  
Similar Morphology ◽  
C Banding ◽  
Heterochromatic Block

Abstract Detailed characterizations of the karyotypes of the Brazilian leptodactylid frogs Pleurodema diplolistris, the only species of Pleurodema not studied cytogenetically so far, and Physalaemus nattereri, a species in the Ph. biligonigerus group, are presented. Both karyotypes had 2n = 22 and their chromosomes had a very similar morphology, except for pair 11, which was metacentric in Pl. diplolistris and telocentric in Ph. nattereri. The localization of nucleolar organizer regions (NORs) and heterochromatic bands allowed the differentiation of chromosomes that were morphologically indistinguishable between these species, such as pairs 1, 3 and 10, which showed interstitial C-bands in Ph. nattereri, and pair 8, that had an NOR and an adjacent C-band in Pl. diplolistris. Pair 8 also has NOR-bearing chromosomes in many other Pleurodema species. However, in these species, the NOR is located proximal to the centromere on the short arm, while in Pl. diplolistris it occurred distally on the long arm, a condition that may be considered a derived state. In Ph. nattereri, the NOR occurred on chromosome 11 and differed from the other species of the Ph. biligonigerus group. In contrast, C-banding revealed a heterochromatic block near the centromere on the short arm of pair 3, a characteristic common to all members of this group of Physalaemus.

scholarly journals Cytogenetical analyses in three fish species of the genus Pimelodus(Siluriformes: Pimelodidae) from rio São Francisco: considerations about the karyotypical evolution in the genus

2005 ◽  
Vol 3 (2) ◽  
pp. 285-290 ◽  
Author(s):  
Caroline Garcia ◽  
Orlando Moreira Filho
Keyword(s):  
Chromosome Pair ◽  
Chromosomal Rearrangements ◽  
Nucleolar Organizer ◽  
Differential Staining ◽  
Nucleolar Organizer Regions ◽  
C Banding ◽  
Heteromorphic Sex Chromosomes ◽  
Chromosomal Markers ◽  
Staining Techniques ◽  
Species Specific

Karyotypes and other chromosomal markers were investigated in three species of the catfish genus Pimelodus, namely P. fur, P. maculatus and Pimelodus sp., from municipality of Três Marias, Minas Gerais, Brazil, using differential staining techniques (C-banding, Silver nitrate and CMA3 staining). The diploid chromosome number was 2n = 56 in P. maculatus and Pimelodus sp., while in P. fur 2n = 54. The karyotype of P. fur consisted in 32M + 8SM + 6ST + 8A with fundamental number (NF) of 100, that of P. maculatus 32M + 12SM + 12A with NF = 112, and that of Pimelodus sp. had 32M + 12Sm + 6ST + 6A with NF = 106.The nucleolar organizer regions (NORs) in all three species were invariably detected in telomeres of longer arm of the 20th chromosome pair. These sites were also positive after CMA3 and C-banding. No heteromorphic sex chromosomes were detected and C-banding pattern was species specific. Inferences about the karyotype differentiation in Pimelodus and putative chromosomal rearrangements are hypohesized.

C-Banding and Nucleolar Organizer Regions of Sphoeroides greeleyi (Tetraodontidae, Tetraodontiformes)

Caryologia ◽  
2002 ◽  
Vol 55 (2) ◽  
pp. 171-174 ◽  
Author(s):  
Mario Jorge Ignacio Brum ◽  
Liliane Cristine Gomes Mota
Keyword(s):  
Nucleolar Organizer ◽  
Nucleolar Organizer Regions ◽  
C Banding

Variation in rDNA Redundancy Level and Nucleolar Organizer Length in Normal and Variant Lines of the Mexican Axolotl

1974 ◽  
Vol 15 (2) ◽  
pp. 239-257
Author(s):  
J. H. SINCLAIR ◽  
CAROLE R. CARROLL ◽  
R. R. HUMPHREY
Keyword(s):  
Genetic Material ◽  
Nucleolar Organizer ◽  
Ambystoma Mexicanum ◽  
The Other ◽  
Colour Pattern ◽  
Nucleolar Organizer Regions ◽  
Wild Type ◽  
Mexican Axolotl ◽  
Apparent Lack ◽  
Heterozygous Condition

The level of redundancy of ribosomal genes, and the relationship of this level to nucleolar formation at different stages of embryonic development, have been examined in the Mexican axolotl, Ambystoma mexicanum. Individuals from 4 inbred stocks were examined, as well as descendants from 2 nucleolar variants which, in the heterozygous condition, are distinguished by exceptionally small nucleoli. Ribosomal RNA-DNA hybridization assays show that one of the 4 wild type lines has only about one-third as much ribosomal DNA (rDNA) as the other three. One of the nucleolar variants has the same level of rDNA as the larger wild-type level; the other variant has the same amount as the smaller ribosomal genome line. Both original nucleolar variants arose as F1 progeny of crosses between a large rDNA genome line and the small genome line. Cytological examination of pregastrula stage embryos from wild type and nucleolar variant lines show that the lengths of the nucleolar organizer regions (NOR) and the sizes of nucleoli formed, are directly correlated with the amount of rDNA present at the nucleolar locus. During gastrulation of the nucleolar variants, however, a transition appears to take place and the amount of rDNA ceases to be the determining factor in nucleolar size. After late gastrula, heterozygous progeny resulting from crosses of either large rDNA genome or small rDNA genome wild type individuals with either nucleolar variant line, have a small and a large nucleolus. The factor or factors associated with this apparent lack of competitive ability of the variant NOR, when opposed to a normal NOR, are unknown. It might be suggested that since the chromosomal alterations which produced the nucleolar variants in both cases eliminated the gene determining the dark colour pattern, they could at the same time have eliminated other genetic material.

scholarly journals Chromosomal variability in the wild ornamental species of Symphysodon (Perciformes: Cichlidae) from Amazon

2008 ◽  
Vol 6 (2) ◽  
pp. 181-190 ◽  
Author(s):  
Débora R. Mesquita ◽  
Jorge I. R. Porto ◽  
Eliana Feldberg
Keyword(s):  
Chromosomal Rearrangements ◽  
Nucleolar Organizer ◽  
Pericentromeric Region ◽  
Nucleolar Organizer Regions ◽  
Large Variability ◽  
Heterochromatic Block ◽  
Chromosomal Heteromorphism ◽  
Chromosomal Variability ◽  
In The Wild ◽  
Ornamental Species

Cytogenetic studies were conducted on three discus species which inhabit the Amazon in Brazil: Symphysodon haraldi from Manacapuru, S. aequifasciatus from Tefé and S. discus from Barcelos. All individuals showed 2n=60 chromosomes, most of them biarmed. No sexual chromosomal heteromorphism was verified. However, different karyotypic formulae, owing to the presence of subtelocentric chromosomes, were verified for S. aequifasciatus and S. discus. One of the karyotypic formulae from S. aequifasciatus (cytotype 2) differs from the others, due to one of the homologues in the first chromosome pair being significantly larger than the other. A large variability was observed toward the nucleolar organizer regions (NOR) of S. haraldi and S. aequifasciatus. Although the number of silver-stained blocks varied from 2 to 5, confirming different NOR patterns, at least seven homologue pairs were involved with NORs. In S. discus only two marks were observed, however two chromosome pairs were involved, characterizing a multiple NOR system for the three species. The heterochromatic blocks were mainly located in the pericentromeric region of all chromosomes but, in some of them, they are also located in the proximal regions, both in the short and long arms. Moreover, in the cytotype 2 from S. aequifasciatus, an interstitial heterochromatic block was observed on the long arm of the largest homologue of the first pair. A direct comparison of karyotypes from more related genera (Heros, Uaru, Mesonauta and Pterophyllum), makes it clear that a succession of chromosomal rearrangements, mainly pericentric inversions, translocations and fissions/fusions occurred resulting in the present diploid number and intraspecific karyological variability found in Symphysodon.

The Hordeum bulbosum 25S-18S rDNA region: comparison with Hordeum vulgare and other Triticeae

2019 ◽  
Vol 74 (11-12) ◽  
pp. 319-328
Author(s):  
Oleg Georgiev ◽  
Kiril Mishev ◽  
Maria Krasnikova ◽  
Meglena Kitanova ◽  
Anna Dimitrova ◽  
...  
Keyword(s):  
Hordeum Vulgare ◽  
18S Rdna ◽  
Intergenic Spacer ◽  
Nucleolar Organizer ◽  
The Other ◽  
Nucleolar Organizer Regions ◽  
Hordeum Bulbosum ◽  
Promoter Sequences ◽  
External Transcribed Spacer

Abstract Hordeum vulgare and Hordeum bulbosum are two closely related barley species, which share a common H genome. H. vulgare has two nucleolar organizer regions (NORs), while the NOR of H. bulbosum is only one. We sequenced the 2.5 kb 25S-18S region in the rDNA of H. bulbosum and compared it to the same region in H. vulgare as well as to the other Triticeae. The region includes an intergenic spacer (IGS) with a number of subrepeats, a promoter, and an external transcribed spacer (5′ETS). The IGS of H. bulbosum downstream of 25S rRNA contains two 143-bp repeats and six 128-bp repeats. In contrast, the IGS in H. vulgare contains an array of seven 79-bp repeats and a varying number of 135-bp repeats. The 135-bp repeats in H. vulgare and the 128-bp repeats in H. bulbosum show similarity. Compared to H. vulgare, the 5′ETS of H. bulbosum is shorter. Additionally, the 5′ETS regions in H. bulbosum and H. vulgare diverged faster than in other Triticeae genera. Alignment of the Triticeae promoter sequences suggests that in Hordeum, as in diploid Triticum, transcription starts with guanine and not with adenine as it is in many other plants.

Nucleolar organizer activity at meiosis in wheat–rye hybrid plants

1986 ◽  
Vol 28 (2) ◽  
pp. 227-234 ◽  
Author(s):  
N. Cuñado ◽  
M. C. Cermeño ◽  
J. Orellana
Keyword(s):  
Silver Staining ◽  
Staining Method ◽  
Nucleolar Organizer ◽  
The Other ◽  
Nucleolar Organizer Regions ◽  
Binucleate Cells ◽  
Hybrid Plants ◽  
Nucleolar Organizer Activity ◽  
Silver Staining Method ◽  
Organizer Activity

Nucleoli and nucleolar organizer regions (NORs) have been studied by a silver staining method in all meiotic stages of wheat–rye hybrid plants. The maximum number of nucleoli per cell scored at meiotic prophase and tapetum binucleate cells indicates that only the NORs of 1B, 6B, and 5D wheat chromosomes are active, whereas that of chromosome IR (SAT) of rye is inactive. However, at diakinesis, metaphase and anaphase meiotic stages only chromosomes 1B and 6B show Ag-NOR as was reported previously in somatic metaphase. The absence of Ag-NOR on chromosome 5D has been imputed to its low nucleolar organizer activity, not detectable by silver staining, because of the small number of rDNA clusters it carries. On the other hand, the meiotic behaviour of chromosomes 1B and 6B has been studied at metaphase I and anaphase I, using the Ag-NORs as cytological markers.Key words: nucleolar organizer, Ag-NOR, meiosis, wheat–rye hybrids.

C-banding pattern and nucleolar organizer regions of Cynoglossus semilaevis Gunther, 1873*

2006 ◽  
Vol 16 (7) ◽  
pp. 769-772
Author(s):  
Wu Di ◽  
Zhang Shicui ◽  
ZHUANG Zhimeng ◽  
Pang Qiuxiang ◽  
Wang Changliu ◽  
...  
Keyword(s):  
Banding Pattern ◽  
Nucleolar Organizer ◽  
Cynoglossus Semilaevis ◽  
Nucleolar Organizer Regions ◽  
C Banding
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