Pairs Of Metacentric Chromosomes Research Articles

Comparative Cytogenetic Study in Four Alopiinae Door Snails (Gastropoda, Clausiliidae)

A cytogenetic study was carried out by means of standard and NOR-FISH staining methods on the chromosomes of four Alopiinae door snails, two species of the Delimini tribe (Siciliaria paestana and Papillifera bidens) and two species of Medorini tribe (Leucostigma candidescens and Medora sp.). The two Delimini species and Medora sp. showed similar karyotypes, concerning the number of chromosomes, 2n = 62, and the first metacentric pair of chromosomes clearly bigger than the other pairs, but differed in the number of the telocentric pairs: none in P. bidens, four in S. paestana and, even, 21 in Medora sp. Leucostigma candidescens had 2n = 48, all biarmed chromosomes. Loci of NORs were on a single medium small chromosome pair in all the four studied species. The obtained results evidence a relevant degree of intergeneric karyotypic diversity in Alopiinae, concerning both chromosome number and/or shape. The data allow us to make a hypothesis on the evolutionary chromosome trends for this door snail subfamily.

Banding Patterns of Three Leafcutter Ant Species of the GenusAtta(Formicidae: Myrmicinae) and Chromosomal Inferences

Among Neotropical ants, the genera Acromyrmex and Atta are of great importance because they include the major agricultural pest species. Regarding the genus Atta, considered one of the most derived of the tribe Attini, cytogenetic data exists for 5 taxa that present 2n = 22 chromosomes; however, information regarding banding patterns is only available for Atta colombica. Cytogenetics has contributed to several aspects related to the family For- micidae, in particular to the understanding of its evolution. Therefore, the aim of this study was to increase the cytogenetic data on Atta sexdens rubropilosa, Atta laevigata and Atta bisphaerica belonging to populations in the state of Minas Gerais, Brazil. The 3 species were characterized as having 2n = 22 chromosomes with a karyotypic formula of 2n = 18m + 2sm + 2st. Using the C-banding technique, small heterochromatic markings were observed in the centromeres of most of the chromosomes. The presence of GC-rich blocks in the interstitial region on the long arm of the fourth pair of metacentric chromosomes was indicated by CMA3 fluorochrome. The data from this study enabled a comparison with Acromyrmex stria- tus, a phylogenetically close species possessing the same chromosome number as the Atta species studied in this work, although clear differences were evident in the morphologies of 2 chromosome pairs and in the distribution and composition of heterochromatin. These results show the constancy of the chromosome number, morphology and banding pattern for the species studied, highlighting the importance of measuring the chromosomes to enable accurate comparison and using banding techniques to compare species of genera with a conserved chromosome number.

Cytogenetic and identification of the nucleolus organizer region in Heliconia bihai (L.) L.

The genus Heliconia is not much studied and the number of existing species in this genus is still uncertain. It is known that this number relies between 150 to 250 species. In Brazil, about 40 species are native and known by many different names. The objective of this paper was to characterize morphometrically and to identify the NOR (active nucleolus organizer regions) by Ag-NOR banding of chromosomes of Heliconia bihai (L) L. Root meristems were submitted to blocking treatment in an amiprofos-methyl (APM) solution, fixed in methanol-acetic acid solution for 24 hours, at least. The meristems were washed in distilled water and submitted to enzymatic digestion with pectinase enzyme. The slides were prepared by dissociation of the root meristem, dried in the air and also on hot plate at 50°C. Subsequently, some slides were submitted to 5% Giemsa stain for karyotype construction and to a solution of silver nitrate (AgNO3) 50% for Ag-NOR banding. The species H. bihai has 2n = 22 chromosomes, 4 pairs of submetacentric chromosomes and 7 pairs of metacentric chromosomes, and graded medium to short (3.96 to 0.67 μM), with the presence of active NOR in pairs 1 and 2 and interphase cells with 2 nucleoli. These are the features of a diploid species.

Distribution and heterogeneity of heterochromatin in the European huchen (Hucho hucho Linnaeus, 1758) (Salmonidae).

The chromosomal characteristics, locations and variations of the heterochromatin were studied in the European huchen (Hucho hucho, Linnaeus, 1758) karyotype using conventional C- banding, endonuclease digestion banding, silver nitrate (AgNO3), chromomycin A3 (CMA3) and DAPI staining techniques. The karyotype consists of 82 chromosomes: 13 pairs of metacentric chromosomes, 2 pairs of submetacentric chromosomes and 26 pairs of subtelo-acrocentric chromosomes (NF = 112). Original data on the chromosomal distribution of segments resistant to Alu I, Dde I and Mbo I restriction endonucleases and identification of the C-banded heterochromatin presented here have been used to characterize the huchen karyotype. On the basis of the banding patterns provided in the course of restriction enzyme digestion, AgNO3/CMA3 staining and C-banding we distinguished twelve types of heterochromatin grouped in four areas of the European huchen chromosomes. One pair of NOR-bearing chromosomes was found to be polymorphic in size and displayed two distinct forms. A combination of various staining techniques provided original data concerning heterochromatin distribution and heterogeneity in the European huchen which enabled better karyotypic definition of this fish species.

Preliminary cytogenetic study and report of ZZ/ZW sex chromosomes in the bullfrog, Hoplobatrachus tigerinus (Anura, Amphibia) from high altitude area of Jammu and Kashmir, India

Cytogenetic study of the Indian Bullfrog, Hoplobatrachus tigerinus was carried out using both conventional staining and banding methods, from Jammu and Kashmir. Karyotypes prepared by conventional staining in both male and female specimens showed diploid chromosome number as 2n = 26 and fundamental arm number as NF = 52. Karyotypes of both the sexes comprised of 13 pairs of biarmed chromosomes divided into two groups: first group of five pairs of larger metacentric or submetacentric chromosomes and second group of eight pairs of smaller metacentric or submetacentric chromosomes. Pair number 2, 3, and 4 among the first group and 8 and 9 among the second group were submetacentric chromosomes. All the other chromosomes in both the groups were metacentric. Meiotic stages observed were leptotene, diakinesis, metaphase-I and metaphase- II, from testicular cells of males. C-banding analysis of the species showed presence of centromeric C-bands in all the chromosomes of both male and female karyotypes. Female karyotype showed presence of completely heterochromatic homologue of the pair no. 8, which represented ZZ/ZW sex chromosome system in the species. NOR-banding showed presence of a pair of nucleolar organizer regions on the long arm of 6th pair in both the sexes.

Molecular cytogenetic study in Octopus (Amphioctopus) areolatus from Japan

Octopus (Amphioctopus) areolatus is an important marine cephalopod in Japan. We examined its diploid chromosome number, karyotype, and genome size (C value), and performed fluorescence in situ hybridization (FISH) using a vertebrate telomeric probe. The diploid chromosome number was 60 in embryonic cells, with 24 pairs of metacentric chromosomes, four pairs of metacentric/submetacentric chromosomes, and two pairs of submetacentric chromosomes. The mean C value was estimated to be 5.47 pg. From these findings, and those reported previously for other octopus species, we suggest that the factor causing the quantum change of C value in O. (A.) areolatus was genome duplication, and not polyploidy. In telomeric FISH analysis, hybridization signals were clearly observed in the telomeric regions of the chromosomes. This is the first report of FISH analysis of cephalopod chromosomes, and our findings suggest that the telomere sequence of O. (A.) areolatus is (TTAGGG)n, which may allow gene mapping in the future.

The role of chromosomal fusion in the karyotypic evolution of the genus Ageneiosus (Siluriformes: Auchenipteridae)

Ageneiosus is the most widely distributed genus of the family Auchenipteridae among South American river basins. Although chromosome studies in the family are scarce, this genus has the largest number of analyzed species, with 2n = 54 to 56 chromosomes, differing from the rest of the family (2n = 58). This study aimed to analyze Ageneiosus inermis from the Araguaia River basin. The diploid number found was of 56 chromosomes. Heterochromatin was allocated in terminal region of most chromosomes, plus a pericentromeric heterochromatic block in pair 1, a pair distinguished by size in relation to other chromosomes pairs. AgNORs were detected in only one submetacentric chromosome pair, which was confirmed by FISH. 5S rDNA was present in only one metacentric chromosome pair. Hybridization with [TTAGGG]n sequence marked the telomeres of all chromosomes, in addition to an ITS in the proximal region of the short arm of pair 1. The repetitive [GATA]n sequence was dispersed, with preferential location in terminal region of the chromosomes. Ageneiosus has a genomic organization somewhat different when compared to other Auchenipteridae species. Evidences indicate that a chromosomal fusion originated the first metacentric chromosome pair in A. inermis, rearrangement which may be a basal event for the genus

Karyotype Analysis of the New Catfish Mystus ngasep (Siluriformes: Bagridae) from Manipur, India

Karyotypic and cytogenetic characteristics of catfish Mystus ngasep, a new species of bagrid catfish described from the Northeast India, Manipur was studied for the first time by examining 200 metaphase spreads chromosome from the kidney cells of 25 healthy specimens. The diploid chromosome number of this species was 2n=56 and the total fundamental arm number was determined as NF=90. The karyotype consisted of 12 Metacentric (m), 22 Submetacentric (Sm), 8 Subtelocentric (St) and 14 Telocentric (t) chromosomes. The chromosome formula can be represented as 2n= 12m + 22Sm + 8St + 14t. No heteromorphic sex chromosomes were cytologically detected. Chromosome number, formula and karyotype of Mystus ngasep differentiate it from other closely related species. The largest chromosome in this species is a pair of metacentric chromosomes and the present study is the first report on the karyology of this particular species which will pave the way for the future studies on this line of karyology for this genus. Thus, this study is of importance in the analysis of karyotypic evolutionary trends, classification and taxonomy of the genus Mystus and better understanding of the karyotype diversity and chromosome evolution processes.

Origin of the chromosomal radiation of Madeiran house mice: a microsatellite analysis of metacentric chromosomes

Chromosome races of Mus musculus domesticus are characterised by particular sets of metacentric chromosomes formed by Robertsonian fusions and whole-arm reciprocal translocations. The Atlantic island of Madeira is inhabited by six chromosome races of house mice with 6-9 pairs of metacentric chromosomes. Three of these races are characterised by the metacentric 3.8 also found elsewhere in the distribution of M. m. domesticus, including Denmark and Spain. We investigated the possibility that metacentric 3.8 was introduced to Madeira during the initial colonisation, as this could have 'seeded' the cascade of chromosomal mutation that is the basis of the extraordinary chromosomal radiation observed on the island. Variation at 24 microsatellite loci mapping to three different chromosomal regions (proximal, interstitial and distal) of mouse chromosomes 3 and 8 was investigated in 179 mice from Madeira, Denmark, Portugal, Spain, Italy and Scotland. Analyses of microsatellite loci closely linked to the centromeres of these chromosomes ('proximal loci') do not support a common evolutionary origin of metacentric 3.8 among Madeiran, Danish and Spanish mouse populations. Our results suggest that Madeiran mice are genetically more similar to standard karyotype mice from Portugal than to metacentric mice from elsewhere. There is expected to be an interruption to gene flow between hybridising metacentric races on Madeira, particularly in the chromosomal regions close to the rearrangement breakpoints. Consistent with this, relating to differentiation involving chromosomes 3 and 8 on Madeira, we found greater genetic structure among races for proximal than interstitial or distal loci.

Karyotype traits in Grindelia squarrosa (Pursh) Dunal (Asteraceae), an invasive plant in Romania

Abstract The description of the karyotype features and idiogram in Grindelia squarrosa (Pursh) Dunal (Asteraceae), an invasive plant in Romania, are reported here for the first time. The diploid chromosome number is 2n=2x=12, in agreement with the data published for the other species of the genus. The karyomorphological data show that the complements of the studied genotypes have small chromosomes (mean chromosome length is X̅±SE=2.56±0.10 μm, and mean length of haploid complements is X̅±SE=15.33±0.69 μm, with a range of variability comprised between 12.87-17.51 μm). The karyotypes are made up of six pairs of metacentric and submetacentric chromosomes, with an identical formula of the diploid complement: KF=2n=12=8m+ 2sm + 2sm-SAT. Satellites are located on the short arms of the chromosomes of pair III. The karyotypes show a relatively high level of intra-specific uniformity as well as similar symmetry patterns (R=1.29-1.53; TF%=38.78-41.57%; AsI%=54.54-57.61%; A1 = 0.24- 0.32; A2=0.08-0.16), belonging to 1A and 2A classes of symmetry. The small size of the chromosomes, the presence of only two chromosome morphometric types, and the preponderance of metacentrics confer a relatively high degree of symmetry to the karyotypes studied.

Conventional and molecular cytogenetics of the pikeperch (Sander luciopercaL.)

Pikeperch (Sander lucioperca L.) is a percid fish species of high commercial value and potential for being aquacultured in Europe. As such, pikeperch needs to be karyologically studied with special attention dedicated to arrangement of the homologous chromosomes into pairs and chromosomal location of the chosen DNA sequences. The karyotype of the pikeperch consists of 48 small chromosomes: One pair of metacentric chromosomes, 15 pairs of submetacentric chromosomes and eight pairs of subtelo-acrocentric chromosomes (FN = 80). Original data on the chromosomal distribution of early and late replication regions, segments resistant to AluI, DdeI, HinfI and HaeIII restriction endonucleases and identification of the C-banded heterochromatin presented herein have been used to arrange pikeperch chromosomes into the karyotype. After Primed in situ labeling (PRINS) technique with primers enabling amplification of 5S rDNA sequences, hybridization spots observed on the short (p) arms of two the largest pikeperch submetacentric chromosomes (no. 2). Fluorescence in situ hybridization (FISH) with telomeric PNA (Peptide Nucleic Acid) probe enabled recognition of the conservative telomeric DNA sequences on the pikeperch chromosomes. No interstitial signals were observed. The specimens studied did not show any morphologically differentiated sex chromosomes.

C-banded karyotype and nucleolar organizer regions of Tinca tinca (Cyprinidae) from Turkey

In this study, conventional Giemsa staining, Silver-Nucleolar Organizer Region (Ag-NOR) and C-banding were applied to eight specimens of Tench, Tinca tinca, of Lake Beysehir, and their detailed cytogenetic properties were investigated. It was determined that all of the chromosomes in karyotypes of the samples investigated were bi-armed (metacentric, submetacentric, subtelocentric). Also a secondary constriction was observed on the short arm of the third pair of chromosomes. No morphological difference was identified between sex chromosomes of male and female specimens. All chromosomes of the specimens had centromeric and pericentromeric C-bands. There was an interstitial band on the short arm of a chromosome pair, while all the short arms of three chromosome pairs were C-positive. Heteromorph C-bands were detected in two chromosome pairs. By Ag-nitrate staining, active NOR was identified on the short arm of the number three metacentric chromosome pair of all specimens. However, this active NOR was not rel...

Morphokaryological variability and divergence of stargazers (Uranoscopus, perciformes) from the Mediterranean Sea basin: I. Divergence and taxonomic state of the Black Sea Stargazer

Based on museum collections, the variability of morphological characters of stargazers (Uranoscopus, Uranoscopidae) from different seas of the Mediterranean Sea basin have been studied. On the basis of the obtained results and data on the karyological divergence of the previously studied populations, stargazers of the Black Sea are regarded as an independent subspecies, Uranoscopus scaber anostomus, differing from the Mediterranean Sea populations in relatively long ventral fins, whose length usually exceeds half of the head length, the presence in most individuals of not less than 12 pyloric caeca, chromosome polymorphism with 2n = 28–32, NF = 50, and the presence in the karyotype of a pair of marker small metacentric chromosomes. Morphological characters suitable for analysis of morphological divergence of populations of the Mediterranean region have been revealed.

The origin of the large metacentric chromosome pair in Chinese medaka (Oryzias sinensis)

Japanese medakas (Oryzias latipes and Oryzias sakaizumii) have 48 chromosomes, while the Chinese medaka (Oryzias sinensis) has 46 chromosomes, including one pair of large metacentric chromosomes. Linkage analysis using O. sakaizumii and O. sinensis strains showed that DNA markers in linkage groups (LG) 11 and 13 were tightly linked. Centromeric genomic clones of LG 11 and 13 derived from an O. latipes strain hybridized across the centromeres of the pair of large metacentric chromosomes in an O. sinensis strain. These results demonstrate that the large metacentric chromosome pair was derived from two pairs of acrocentric chromosomes (LG 11 and 13) through Robertsonian fusion.

Karyotype analysis in some species of Consolida (Ranunculaceae) from Iran

AbstractConsolida (dc.) S. F. Gray belongs to Ranunculaceae. The genus includes about 52 species worldwide. Here we report the diploid chromosome number and chromosome size and morphology for six Consolida species. For C. anthoroidea, C. leptocarpa, C. paradoxa and C. rugulosa the diploid chromosome number is reported for the first time. All investigated species have a diploid chromosome number of 2n = 2x = 16, except for C. persica having 2n = 2x = 14. The karyotypes of all six taxa are asymmetric, consisting of all four major chromosome types: metacentric, submetacentric, subtelocentric and telocentric chromosome type. However, considering the karyotype formula, all six species could be distinguished. In all taxa, metacentric chromosome pair 1 possesses a satellite. The only exception is C. rugulosa having an additional satellite positioned on metacentric chromosome pair 2. Karyotype data allow the separation of Aconitella from Consolida. Karyotype data plus morphological evidence support the reduction of C. paradoxa to formae level of C. rugulosa. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Karyological comparisons of the European hare (Lepus europaeus Pallas, 1778) from the Asian part of Turkey, with morphological contributions

We focused on a comparison of karyological data for the European brown hare Lepus europaeus, from the Asian part of Turkey. In Turkish L. europaeus, the diploid number (2n), the fundamental number of chromosomal arms (FN) and the number of autosomal arms (FNa) were determined to be 2n=48, 84 and 80, respectively. The autosomes are composed of three pairs of metacentric chromosomes, four pairs of submetacentric chromosomes, ten pairs of subtelocentric chromosomes and six pairs of acrocentric chromosomes. The X chromosome was a medium-large submetacentric and the Y chromosome was a very small acrocentric. This is the third report for L. europaeus from Turkey and confirmed the previous results with regard to 2n. However, when comparing our findings with those of other authors, there were karyotypic differences among the chromosomes. These differences were related to the number of chromosome arms. Additionally, we present the skull measurements of seven samples for the Turkish brown hare collected from three localities, and these measurements conformed to those of previous studies.

Classical and molecular cytogenetics of Khawia sinensis (Cestoda: Caryophyllidea), invasive parasite of carp, Cyprinus carpio

Chromosomes of the invasive tapeworm Khawia sinensis (Caryophyllidea), the specific parasite of common carp, were analyzed by means of conventional Giemsa staining and using fluorescent DAPI and YOYO-1 dyes, silver staining, and fluorescent in situ hybridization (FISH) with 18S rDNA probe. The karyotype is composed of eight pairs of metacentric and telocentric chromosomes (2n = 16, n = 3m + 5t, TCL = 42.54 μm). Constitutive heterochromatin was located at pericentromeric regions of all pairs, except for the largest metacentric pair (no. 1), which possessed no DAPI-positive band. FISH with rDNA probe revealed that both homologues of chromosome pair no. 6 carry a cluster of ribosomal arrays, which were located interstitially close to the centromere. Present results are compared with previous cytogenetic data on Khawia spp., and comments are made on the karyotypes with respect to their phylogenetic links.

Differentiation of repetitive DNA sites and sex chromosome systems reveal closely related group in Parodontidae (Actinopterygii: Characiformes)

Parodon and Apareiodon lack sufficiently consistent morphological traits to be considered a monophyletic group in Parodontidae. Species within this family are either sex-homomorphic or sex-heteromorphic (i.e., lacking a differentiated sex chromosome system, ZZ/ZW or ZZ/ZW(1)W(2)). In this study, a DNA fragment from the heterochromatin segment of the W chromosome of Apareiodon ibitiensis (named WAp) was microdissected and used for in situ mapping of nine Parodontidae species. The species were also characterized using a satellite DNA probe (pPh2004). The species were phylogenetically clustered according to 17 characters, which were examined by both classical and molecular cytogenetic techniques. Given the present results, the single ZZ/ZW sex chromosome system seems to have been derived from a paracentric inversion of a terminal WAp site onto the proximal regions of the short arms of a metacentric chromosome pair, followed by WAp site amplification. We reason that these events restrained recombination and favored differentiation of the W chromosome in some species. Moreover, co-hybridization experiments targeting the WAp and pPh2004 repetitive DNA sites of A. affinis suggest that the ZZ/ZW(1)W(2) sex chromosomes of this species may have arisen from a translocation between the proto-sex chromosome and an autosome. Our phylogenetic analysis corroborates the hypothesis of sex chromosome differentiation and establishes groups of closely related species. The phylogenetic reorganization in response to these new data supports the presence of internal monophyletic groups within Parodontidae.

DNA methylation patterns of Brachypodium distachyon chromosomes and their alteration by 5-azacytidine treatment

Sequential immunolocalisation of 5-methylcytosine (5-MeC) and fluorescence in situ hybridisation with chromosome-specific BAC clones were performed on Brachypodium distachyon mitotic metaphase chromosomes to determine specific DNA methylation patterns of each chromosome in the complement. In the majority of cells examined, chromosomes Bd4 and Bd5, which bear the loci of 5S and 35S ribosomal DNA, respectively, had characteristic 5-MeC patterns. In contrast, the distribution of 5-MeC along the metacentric chromosome pairs Bd1, Bd2 and Bd3 was more variable. There were numerous differences in distribution of methylated sites between homologous chromosomes as well as between chromosome arms. Some chromosome sites, such as pericentromeric regions, were highly methylated in all chromosomes. Additionally, the influence of a hypomethylating agent, 5-azacytidine, on B. distachyon chromosome methylation patterns was confirmed. It was found that some chromosome pairs underwent demethylation more easily than others, but there was no apparent regularity in demethylation of particular chromosome segments.

Cytogenetic characterization and mapping of rDNAs, core histone genes and telomeric sequences in Venerupis aurea and Tapes rhomboides (Bivalvia: Veneridae)

We describe the chromosomal location of GC-rich regions, 28S and 5S rDNA, core histone genes, and telomeric sequences in the veneroid bivalve species Venerupis aurea and Tapes (Venerupis) rhomboides, using fluorochrome staining with propidium iodide, DAPI and chromomycin A3 (CMA) and fluorescent in situ hybridization (FISH). DAPI dull/CMA bright bands were coincident with the chromosomal location of 28S rDNA in both species. The major rDNA was interstitially clustered at a single locus on the short arms of the metacentric chromosome pair 5 in V. aurea, whereas in T. rhomboides it was subtelomerically clustered on the long arms of the subtelocentric chromosome pair 17. 5S rDNA also was a single subtelomeric cluster on the long arms of subtelocentric pair 17 in V. aurea and on the short arms of the metacentric pair 9 in T. rhomboides. Furthermore, V. aurea showed four telomeric histone gene clusters on three metacentric pairs, at both ends of chromosome 2 and on the long arms of chromosomes 3 and 8, whereas histone genes in T. rhomboides clustered interstitially on the long arms of the metacentric pair 5 and proximally on the long arms of the subtelocentric pair 12. Double and triple FISH experiments demonstrated that rDNA and H3 histone genes localized on different chromosome pairs in the two clam species. Telomeric signals were found at both ends of every single chromosome in both species. Chromosomal location of these three gene families in two species of Veneridae provides a clue to karyotype evolution in this commercially important bivalve family.