Loss of nucleolar organizer regions during chromosomal evolution in the South American cricetid Graomys griseoflavus

Genetica ◽  
1996 ◽  
Vol 98 (1) ◽  
pp. 53-57 ◽  
Author(s):  
Andr�s Zambelli ◽  
Lidia Vidal-Rioja
Keyword(s):  
Nucleolar Organizer ◽  
Chromosomal Evolution ◽  
Nucleolar Organizer Regions ◽  
South American ◽  
The South

scholarly journals Chromosomal evolution in the South American Nymphalidae

Hereditas ◽  
2007 ◽  
Vol 144 (4) ◽  
pp. 137-148 ◽  
Author(s):  
Keith S. Brown Jr. ◽  
André Victor Lucci Freitas ◽  
Niklas Wahlberg ◽  
Barbara Von Schoultz ◽  
Anja O. Saura ◽  
...  
Keyword(s):  
Chromosomal Evolution ◽  
South American ◽  
The South

scholarly journals Diversity and chromosomal evolution in the genus Ancistrus Kner, 1854 (Loricariidae: Ancistrini) from three hydrographic basins of Mato Grosso State, Brazil

2013 ◽  
Vol 11 (1) ◽  
pp. 125-131 ◽  
Author(s):  
Sandra Mariotto ◽  
Liano Centofante ◽  
Orlando Moreira-Filho
Keyword(s):  
Diploid Number ◽  
Nucleolar Organizer ◽  
Single Species ◽  
Chromosomal Evolution ◽  
Nucleolar Organizer Regions ◽  
Mitotic Chromosomes ◽  
Evolutionary Mechanisms ◽  
Mato Grosso ◽  
Silver Nitrate Staining ◽  
Cytogenetic Analyses

Cytogenetic analyses were carried out in 117 specimens of seven species of the genus Ancistrus from three hydrographic in Mato Grosso State: Paraguay, Araguaia-Tocantins and Amazon basins. Conventional cytogenetic techniques were used to obtain mitotic chromosomes. C-banding was performed to detect heterochromatic regions and silver nitrate staining was used to identify nucleolar organizer regions (Ag-NORs). The counted and paired chromosomes revealed diploid numbers ranging from 2n = 40 to 2n = 54 with karyotype formulae varying from FN = 80 to FN = 86. Single marks in distinct chromosomes identified the nucleolar organizer regions. The constitutive heterochromatin was scarce in the diploid number from 2n = 50 to 2n = 54 and conspicuous blocks were observed in a single species with 2n = 40 chromosomes. These data corroborate the hypotheses of reduction of diploid number in species with derived features such as presence of sex chromosomes and polymorphisms, besides allowing inferences about the evolutionary mechanisms and the ancestor karyotype that favored the diversification of this important genus in the tribe Ancistrini.

Genome size, fluorochrome banding, and karyotype evolution in some Hypochoeris species

Genome ◽  
1995 ◽  
Vol 38 (4) ◽  
pp. 689-695 ◽  
Author(s):  
M. Cerbah ◽  
J. Coulaud ◽  
B. Godelle ◽  
S. Siljak-Yakovlev
Keyword(s):  
Flow Cytometry ◽  
Genome Size ◽  
Dna Content ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
Nucleolar Organizer ◽  
Phylogenetic Position ◽  
Nucleolar Organizer Regions ◽  
Fluorochrome Banding ◽  
South American

Four South American and two European species of Hypochoeris (Asteraceae) were studied using fluorochrome banding, and genome size was determined by flow cytometry, in order to obtain information about microevolution in this genus and about its primary origin. Fluorochrome banding patterns showed GC-rich repeated sequences, particularly around the nucleolar organizer regions. Few differences appeared among the South American species. Nevertheless, determination of nuclear DNA content and base composition revealed significant differences among these species. The phylogenetic position of Hypochoeris robertia, which has the smallest DNA content, is discussed with regard to chromosome evolution in this genus.Key words: Hypochoeris, Asteraceae, fluorochromes, flow cytometry, nucleolar organizer regions, microevolution.

scholarly journals Chromosomal characterization of three native and one cultivated species of Lathyrus L. in Southern Brazil

1999 ◽  
Vol 22 (4) ◽  
pp. 557-563 ◽  
Author(s):  
Alice Battistin ◽  
Elaine Biondo ◽  
Liliana Gressler May Coelho
Keyword(s):  
Interphase Nucleus ◽  
Nucleolar Organizer ◽  
Chromosome Length ◽  
Nucleolar Organizer Regions ◽  
South American ◽  
South American Species ◽  
Metaphase Chromosomes ◽  
Interphase Nuclei ◽  
Cultivated Species

Mitotic metaphase chromosomes and interphase nuclei of nine populations of three South American species of Lathyrus (L. pubescens, L. nervosus and L. crassipes) and six populations of the cultivated species L. odoratus were analyzed. All populations had 2n = 2x = 14 chromosomes. There were significant differences among populations within each species and among species in the number of metacentric, submetacentric and subtelocentric chromosomes, the number and location of secondary constrictions, chromosome length (longest and shortest), total haploid complement, arm ratio, and centromeric index. L. odoratus showed the highest tendency towards karyotype symmetry whereas the three South American species showed a moderate tendency towards asymmetry, with L. pubescens being the most asymmetrical. Silver staining was used to identify the nucleolar organizer regions (NORs) and the number of nucleoli per interphase nucleus in each species. In L. pubescens and L. nervosus, the NORs were located on the secondary constriction of the long arm of pair 7, in L. crassipes, the NOR was proximal being located in the pair of metacentric chromosomes, and in L. odoratus there were four terminal NORs on the short arms of pairs 4 and 5. The four species had a maximum of four nucleoli per interphase nucleus, indicating the presence of four regions with active ribosomal genes in each case.

scholarly journals Sequential Steps of Chromosomal Differentiation in Atlantic Surgeonfishes: Evolutionary Inferences

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Paulo Roberto Antunes de Mello Affonso ◽  
Maria Aparecida Fernandes ◽  
Josivanda Santos Almeida ◽  
Wagner Franco Molina
Keyword(s):  
Molecular Phylogeny ◽  
Nucleolar Organizer ◽  
Chromosomal Evolution ◽  
Nucleolar Organizer Regions ◽  
Similar Distribution ◽  
Noncoding Sequences ◽  
Pericentric Inversions ◽  
Chromosomal Differentiation ◽  
Chromosomal Data

Surgeonfishes are a species-rich group and a major biomass on coral reefs. Three species are commonly found throughout South Atlantic,Acanthurus bahianus,A. chirurgus, andA. coeruleus. In this paper, we present the first cytogenetic data of these species, revealing a sequential chromosomal diversification.A. coeruleuswas characterized by a relatively conserved karyotype evolved by pericentric inversions of some pairs (2n=48, 2sm + 4st + 42a). In contrast, the karyotypes ofA. bahianus(2n=36) andA. chirurgus(2n=34) were highly differentiated by the presence of six large metacentric pairs inA. bahianus(12m + 2sm + 4st + 18a) andA. chirurgus(12m + 2sm + 4st +1 6a) probably derived by chromosomal fusions that corroborate their closer relationship. A discerniblein tandemfusion represents an autapomorphic character toA. chirurgus. In spite of macrostructure variation, single nucleolar organizer regions (NORs) on short arms of a subtelocentric pair and similar distribution of C-bands were observed in the three species. Overlapping of chromosomal data with molecular phylogeny indicated pericentric inversions which took place nearly at 19 Ma while centric fusions are as recent as 5 Ma. A physical mapping of coding and noncoding sequences inAcanthuruscould clarify the role of additional rearrangements during their chromosomal evolution.

scholarly journals Chromosomal evolution in the South American Riodinidae (Lepidoptera: Papilionoidea)

Hereditas ◽  
2012 ◽  
Vol 149 (4) ◽  
pp. 128-138 ◽  
Author(s):  
Keith S. Brown ◽  
Barbara von Schoultz ◽  
Anja O. Saura ◽  
Anssi Saura
Keyword(s):  
Chromosomal Evolution ◽  
South American ◽  
The South

Electron Microscopic investigation of crooke’s change in the pituitaries of patients with hypercorticism

1989 ◽  
Vol 47 ◽  
pp. 848-849
Author(s):  
E. Horvath ◽  
K. Kovacs ◽  
L. Stefaneanu ◽  
N. Losinski
Keyword(s):  
Nucleolar Organizer ◽  
Microscopic Investigation ◽  
Electron Microscopic Investigation ◽  
Ectopic Acth Syndrome ◽  
Nucleolar Organizer Regions ◽  
Electron Microscopic ◽  
Human Pituitary ◽  
Ectopic Acth ◽  
Crooke’S Hyalinization

Human pituitary corticotropins have unique morphologic markers: bundles of type-1 filaments, measuring approximately 70 A in width and representing cytokeratin. The extreme ring-like accumulation of type-1 filaments, known as Crooke's hyalinization, signals functional suppression of the corticotropins and occurs in endogenous and exogenous glucocorticoid excess, caused by ACTH-secreting pituitary adenoma, glucocorticoid secreting adrenocortical tumor, ectopic ACTH-syndrome and administration of pharmacologic doses of glucocorticoids. Cells of autonomous corticotroph adenomas usually do not show Crooke's hyalin change. A minority of these tumors, however, retains sensitivity to the negative feed-back effect of elevated blood glucocorticoid levels and display typical Crooke’s change.In the present study pituitary corticotropins in various phases of Crooke's hyalinization were investigated in patients with glucocorticoid excess of various origin, applying histology, immunocytochemistry, count of argyrophilic nucleolar organizer regions (AgNOR), and transmission electron microscopy.

A role for upstream binding factor in organizing ribosomal gene chromatin

2006 ◽  
Vol 73 ◽  
pp. 77-84 ◽  
Author(s):  
Jane E. Wright ◽  
Christine Mais ◽  
José-Luis Prieto ◽  
Brian McStay
Keyword(s):  
Nucleolar Organizer ◽  
Ribosomal Gene ◽  
Rna Polymerase I ◽  
Nucleolar Organizer Regions ◽  
Binding Factor ◽  
Upstream Binding Factor ◽  
Acrocentric Chromosomes ◽  
Polymerase I ◽  
Secondary Constrictions ◽  
Active Nors

Human ribosomal genes are located in NORs (nucleolar organizer regions) on the short arms of acrocentric chromosomes. During metaphase, previously active NORs appear as prominent chromosomal features termed secondary constrictions, which are achromatic in chromosome banding and positive in silver staining. The architectural RNA polymerase I transcription factor UBF (upstream binding factor) binds extensively across the ribosomal gene repeat throughout the cell cycle. Evidence that UBF underpins NOR structure is provided by an examination of cell lines in which large arrays of a heterologous UBF binding sequences are integrated at ectopic sites on human chromosomes. These arrays efficiently recruit UBF even to sites outside the nucleolus, and during metaphase form novel silver-stainable secondary constrictions, termed pseudo-NORs, that are morphologically similar to NORs.

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