Similar Chromosome Morphology Research Articles

Cytogenetic Analysis of the Asian Box Turtles of the Genus Cuora (Testudines, Geoemydidae).

The Asian box turtle genus Cuora currently comprises 13 species with a wide distribution in Southeast Asia, including China and the islands of Indonesia and Philippines. The populations of these species are rapidly declining due to human pressure, including pollution, habitat loss, and harvesting for food consumption. Notably, the IUCN Red List identifies almost all species of the genus Cuora as Endangered (EN) or Critically Endangered (CR). In this study, we explore the karyotypes of 10 Cuora species with conventional (Giemsa staining, C-banding, karyogram reconstruction) and molecular cytogenetic methods (in situ hybridization with probes for rDNA loci and telomeric repeats). Our study reveals a diploid chromosome number of 2n = 52 chromosomes in all studied species, with karyotypes of similar chromosomal morphology. In all examined species, rDNA loci are detected at a single medium-sized chromosome pair and the telomeric repeats are restricted to the expected terminal position across all chromosomes. In contrast to a previous report, sex chromosomes are neither detected in Cuora galbinifrons nor in any other species. Therefore, we assume that these turtles have either environmental sex determination or genotypic sex determination with poorly differentiated sex chromosomes. The conservation of genome organization could explain the numerous observed cases of interspecific hybridization both within the genus Cuora and across geoemydid turtles.

Genome size and cytomolecular diversification in two species of the South African endemic genus Tulbaghia L. (Allioideae, Amaryllidaceae)

Tulbaghia L. is a South African genus of Allioideae, Amaryllidaceae, which includes circa 25 species with similar karyotypes, all of them with 2n = 12 large chromosomes, predominantly metacentric to submetacentric. This karyotype stability contrasts with the high variability in chromosome number and morphology reported for its South American sister group, the tribe Gilliesieae. Aiming to understand the chromosome evolution in Tulbaghia, we did a karyotype analysis of T. violacea Harv. and T. simmleri Beauverd, looking for a precise characterization of chromosomal length, distribution of heterochromatin, rDNA sites, telomeric DNA sites, and genome size. The two species displayed similar chromosome morphology and size, but the genome size was smaller in T. simmleri (2C = 38.88 pg) than in T. violacea (2C = 43.48 pg). Both species had the Arabidopsis-type (T3AG3)n and the vertebrate-type (T2AG3)n telomeric motifs in all chromosome termini, a single pair of CMA+ bands colocalized with 35S rDNA sites and one pair of 5S rDNA sites neutrally stained with CMA. Additionally, T. simmleri had 12 large CMA+ bands colocalized with 5S rDNA sites and an extra pair of small CMA+ bands. In spite of the morphological karyotype similarity among Tulbaghia species, our data indicate that small chromosomal and genomic changes are actively acting on the karyotype differentiation of these species. Features such as chromosome size and morphology, genome size, number/distribution of rDNA sites and telomeric DNA resemble Tulbaghia karyotypes to those of other genera of tribes Allieae and Gilliesieae, reinforcing the relationship among the three tribes of the subfamily Allioideae.

Karyomorphological analysis of four species of Zingiberaceae from Thailand

Somatic chromosome numbers and karyomorphological details of for four species of Thai Zingiberaceae belonging to the genera Alpinia, Elettariopsis and Kaempferia were determined using tissue samples from root tips. The chromosome numbers of both Alpinia siamensis and Elettariopsis biphylla were 2n = 48, for Kaempferia marginata it was 2n = 42, and that of Kaempferia rotunda was 2n = 30. We observed asymmetrical karyotypes, including metacentric (m), submetacentric (sm) and telocentric (t) chromosomes in some species. The karyotype formulae were as follows: A. siamensis 2n = 48 = 42m + 6sm; E. biphylla 2n = 48 = 18m + 26sm + 4t; K. marginata 2n = 42 = 28m + 14sm and K. rotunda 2n = 30 = 14m + 16sm. Telocentric chromosomes were observed in the 21st and 22nd chromosome pairs in E. biphylla. The karyotypes of K. rotunda and K. marginata detailed here are the first report. The chromosome analysis shows that these species differ in the chromosome number and the total chromosome length, albeit had similar chromosome morphology and asymmetry indexes.

Unique sex chromosome systems in Ellobius: How do male XX chromosomes recombine and undergo pachytene chromatin inactivation?

Most mammalian species have heteromorphic sex chromosomes in males, except for a few enigmatic groups such as the mole voles Ellobius, which do not have the Y chromosome and Sry gene. The Ellobius (XX ♀♂) system of sex chromosomes has no analogues among other animals. The structure and meiotic behaviour of the two X chromosomes were investigated for males of the sibling species Ellobius talpinus and Ellobius tancrei. Their sex chromosomes, despite their identical G-structure, demonstrate short synaptic fragments and crossover-associated MLH1 foci in both telomeric regions only. The chromatin undergoes modifications in the meiotic sex chromosomes. SUMO-1 marks a small nucleolus-like body of the meiotic XX. ATR and ubiH2A are localized in the asynaptic area and the histone γH2AFX covers the entire XX bivalent. The distribution of some markers of chromatin inactivation differentiates sex chromosomes of mole voles from those of other mammals. Sex chromosomes of both studied species have identical recombination and meiotic inactivation patterns. In Ellobius, similar chromosome morphology masks the functional heteromorphism of the male sex chromosomes, which can be seen at meiosis.

Cytotaxonomy of Eurypyga helias (Gruiformes, Eurypygidae): First Karyotypic Description and Phylogenetic Proximity with Rynochetidae.

The sunbittern (Eurypyga helias) is a South American Gruiformes, the only member of Family Eurypigidae. In most phylogenetic proposals, it is placed in a more distant position than other families of the so-called “core Gruiformes”. Different studies based on molecular, morphological and biogeographical data suggest that the Eurypigidae is closely related to the kagu (Rhynochetos jubatus), the only species in Rynochetidae, another family not included in the core Gruiformes. Here, the karyotype of the sunbittern is described for the first time, by classical and molecular cytogenetics, using whole chromosome probes derived from Gallus gallus and Leucopternis albicollis. We found a diploid number of 80, with only one pair of biarmed autosomal macrochromosomes, similar to that observed in the kagu. Chromosome painting revealed that most syntenies found in the avian putative ancestral karyotype (PAK) were conserved in the sunbittern. However, PAK1, PAK2, and PAK5 corresponded to two chromosome pairs each. Probes derived from L. albicollis confirm that fissions in PAK1 and PAK2 were centric, whereas in PAK5 the fission is interstitial. In addition, there is fusion of segments homologous to PAK2q and PAK5. From a phylogenetic point of view, comparisons of our results with two other Gruiformes belonging to family Rallidae suggest that the PAK5q fission might be a synapomorphy for Gruiformes. Fissions in PAK1 and PAK2 are found only in Eurypigidae, and might also occur in Rynochetidae, in view of the similar chromosomal morphology between the sunbittern and the kagu. This suggests a close phylogenetic relationship between Eurypigidae and Rynochetidae, whose common ancestor was separated by the Gondwana vicariancy in South America and New Caledonia, respectively.

Cytotaxonomy of two species of genus Chrysolaena H. Robinson, 1988 (Vernonieae, Asteraceae) fromNortheast Paraguay.

Chromosome counts and karyotypes of two species of Chrysolaena H. Robinson 1988 are presented in this paper. Mitotic analysis revealed that both taxa have x=10, a basic chromosome number considered characteristic of the genus. The chromosome number and the karyotype of Chrysolaena cristobaliana are reported for the first time, as well as a new cytotype and the karyotype of Chrysolaena sceptrum. Chrysolaena cristobaliana showed heptaploid cytotype with 2n=7x=70 and a karyotype composed of 46 m + 24 sm chromosomes. On the other hand, Chrysolaena sceptrum presented tetraploid cytotype with 2n=4x=40 and a karyotype with 30 m + 10 sm chromosomes. Accessory chromosomes were observed in cells of both species. The chromosome analysis showed that these species differ in the chromosome number and the total chromosome length, although they showed similar chromosome morphology and asymmetry indexes. The results support the use of chromosome data in taxonomic treatments of the American members of the tribe Vernonieae.

Karyotype studies endemic plant speciesAstragalus sericeocanusGontsch.(Fabaceae) around Lake Baikal, Siberia

A study of the karyotype and chromosome of six Astragalus sericeocanus populations from different parts of Lake Baikal’s shoreline was undertaken. Each population had the same chromosome number, 2n = 16. The population was divided into three groups depending on the karyotype formulae 2n = 16=8m+8sm, 2n = 16=6m+10sm and 2n = 16=4m+12sm. The analysis of the karyotype asymmetry indexes showed that population on Millionnyi Island had the most asymmetrical and evolutionary karyotype and the population along the River Turka had the most symmetrical karyotype in all of the populations. The plants from all studied populations have similar chromosome morphology.

Cytogenetics and sperm ultrastructure of Atelopus spumarius (Anura, Bufonidae) from the Brazilian Amazon.

The current taxonomy of most Atelopus species is based on morphological and color data only. Recent studies suggest that A. spumarius may represent a species complex assigned under the same name. Karyotypic data and description of sperm ultrastructure for 13 specimens of A. spumarius are presented here for the first time. A chromosomal analysis revealed 2n = 22 chromosomes, with centromeric heterochromatin in all pairs and a nucleolar organizer region (NOR) on the telomere of pair 7. The sperm was of the bufonoid type, presenting a filiform nucleus covered by an acrosomal complex and a mitochondrial collar in the neck region. The tail was composed of an axoneme, an undulating membrane and an axial rod. A karyotype analysis of A. spumarius showed the same chromosome number and similar chromosomal morphology as described for congeneric species, with slight differences probably resulting from pericentric inversions. The NOR location (on pair 7) was the same as that observed for species belonging to the genus Rhinella. The spermatological findings indicate a close relationship between Atelopus and the bufonoid lineage. The present data are useful for reference in future studies to determine whether more than one species are assigned to A. spumarius.

Environmental Toxicity Monitoring of Nanomaterials using Vicia Faba GENE-TOX Assay

Environmental Toxicity Monitoring of Nanomaterials using Vicia Faba GENE-TOX Assay

Generation of multicolor banding probes for chromosomes of different species

BackgroundThe multicolor banding (MCB/mBAND) technique provides a unique opportunity to characterize intrachromosomal rearrangements and to determine chromosomal breakpoints. Until recently, MCB probes have only been available for human and some murine chromosomes. Generation of MCB probes for chromosomes of other species, useful and required in many cytogenetics research fields, was limited by technical difficulties. MCB probes are established by chromosome microdissection followed by whole genomic DNA amplification. However, unambiguous identification of the target chromosome is required for MCB-probe establishment. Previously proposed protocols suggested G-banding staining or preliminary FISH with whole chromosome paints (WCP) as methods to identify the chromosome of interest.ResultsHere we present a complete workflow for MCB probe generation for those cases and species where chromosome morphology is too challenging to recognize target chromosomes by conventional methods and where WCP probes are not available. The workflow was successfully applied for murine chromosomes that are difficult to identify unambiguously. Additionally, we showed that glass-needle based microdissection enables establishment of a whole set of WCP paints by microdissection of individual chromosomes of a single metaphaseConclusionsThe present method can be applied for generation of whole or region-specific DNA probes for species, where karyotyping of G-banded chromosomes is challenging due to similar chromosome morphology and/or chromosome banding patterns.

NOR Dispersion, Telomeric Sequence Detection in Centromeric Regions and Meiotic Multivalent Configurations in Species of the Aplastodiscus albofrenatus Group (Anura, Hylidae)

In the present study, we examined the chromosome number and morphology, heterochromatin pattern, and location of the nucleolar organizer region (NOR) and telomeric sequences in Aplastodiscus albofrenatus, A. arildae, A. ehrhardti and A. eugenioi in order to cytogenetically characterize the Aplastodiscus albofrenatus group. The 4 species analyzed in this study had diploid numbers of 2n = 22 and very similar chromosome morphology. These species could be differentiated based on the distribution and amount of heterochromatin and the location of the nucleolar organizer region (NOR). Six of the 8 A. albofrenatus individuals had an NOR polymorphism previously unknown in anurans since only one of the homologs of pairs 1 and 7 was stained. In the other 2 specimens, the NOR occurred on both homologs of pair 7. In A. ehrhardti, pairs 6 and 10 were stained by the AgNOR technique, but only pair 6 was confirmed by in situ hybridization. The NOR was located on pair 10 in A. arildae and on pair 7 in A. eugenioi. In A. albofrenatus and A. arildae, multivalent rings involving NOR-containing chromosomes were observed during prophase I of meiosis. The telomeric probe identified the telomeres in all species and also centromeric regions in the chromosomes of A. albofrenatus and A. arildae, which were coincident with centromeric heterochromatin. The conserved chromosomal morphology seen mainly in the first 7 pairs among species of the A. albofrenatus group suggests that all of these species probably originated from a common ancestral karyotype and that chromosomal rearrangements resulted in karyotype differentiation, with changes in NOR location, as well as telomeric and heterochromatin dispersal.

Identification of a Molecular Marker and Chromosome Mapping of the 5S rRNA Gene inAllium sacculiferum

The 5S rRNA gene in higher eukaryotes is organized into repeated units of tandem array that comprise a conserved 120-bp coding region and a non-transcribed spacer (NTS) of variable length with nucleotides. The allotetraploid genome ofAllium sacculiferum consists of two unknown diploids (2n=32). Analyses have not been successful toward clarifying the origin of each genome due to their similar chromosome morphology and unmatched C-banding patterns. We PCR-amplified the coding and NTS regions of its 5S rRNA genes, cloned them into vectors, and determined their DNA sequences. Interestingly, the aligned sequences of the NTS clones could be divided into two distinctive groups based on the existence of a 3-bp CCT insertion/deletion at the beginning of the NTS region. This feature makes it an important genetic marker for distinguishing the origin of theA. sacculiferum chromosomes. Furthermore, by applying fluorescencein situ hybridization, we located the 5S rRNA gene loci on Chromosomes 5, 7, 8, 9, and 14; their distribution is unique toA. sacculiferum. These data support the idea that one set of this genome has originated from a CCT-containing close relative --A. deltoid-fistulosum -- and that the NTS region may be used as a molecular marker for identifying parental lines for the allotetraploidityof A. sacculiferum.

Karyological studies in Chilean species of Bomarea and Leontochir (Alstroemeriaceae)

Species from two genera belonging to the Alstroemeriaceae, Bomarea and Leontochir, were cytogenetically studied and compared to determine their detailed karyotypic composition. Bomarea is a polytypic genus represented by 100 species, with a distribution range from Mexico and Antilles (24°N) to Argentina (29°S) and Chile (17–40°S). In contrast Leontochir is a monotypic genus, endemic to the coastal area of the Atacama Desert in Chile (28°S). Bomarea salsilla, B. involucrosa, and Leontochir ovallei have a karyotype 2n = 18 with similar chromosome morphology. These data confirm the close relationship between both genera, suggested by earlier studies.

Chromosomal Study of Colostethus brunneus from the Type Locality and Two Related Species (Anura – Dendrobatidae)

In this paper, we report a chromosomal study of three Brazilian species of Colostethus, C. brunneus from the type locality, Colostethus sp. (aff. trilineatus), and Colostethus sp., which is morphologically similar to C. brunneus. The diploid number for C. brunneus was 2n = 24 chromosomes, in agreement with that previously described for specimens from Peru. Colostethus sp. (aff. trilineatus) and Colostethus sp. showed a very similar karyotype with 22 chromosomes. The NOR was located on pair 3 in C. brunneus, on pair 4 in Colostethus sp. (aff. trilineatus), and on pair 2 in Colostethus sp. In one specimen of Colostethus sp., an additional NOR site was located on pair 7 in only one of the homologs. This extra Ag-NOR site was confirmed by FISH using an rDNA probe. In addition to the NOR location, the C-banding pattern was also species-specific, despite the similar chromosomal morphology of the species. These results indicate that although these species may be closely related, there is a clear dichotomy in their chromosome number.

C‐Banding Analyses of Bromus inermis Genomes

Smooth bromegrass (Bromus inermis Leyss.) has both tetraploid (2n = 28) and octaploid (2n = 56) ploidy levels that have been difficult to characterize cytogenetically because of similar chromosome morphology. Objectives of this study were to identify individual chromosomes of tetraploid and octaploid B inermis with C‐banding procedures along with chromosome length and arm length ratios, develop more detailed karyotypes than those previously available, and use the karyotypes to examine the genomic relationship of tetraploid and octaploid B inermis Root tips of the plants from four tetraploid and three octaploid accessions were used to produce chromosome squash preparations for cytogenetic analysis. The tetraploid B inermis genome consisted of 12 chromosomes with a telomeric band on each arm and sixteen chromosomes with only one telomeric band on one arm. All of the chromosomes of the tetraploid form, except for four chromosomes, were identified by C‐banding patterns, chromosome length, and arm length ratio. The octaploid B inermis genome consisted of four chromosomes with no C‐bands, ≈14 chromosomes with two telomeric bands, and ≈38 chromosomes with only one telomeric band on either the short or long arm. The combined use of C‐banding, chromosome size, and arm length ratio only enabled groups of 2, 4, 6, or 8 similar chromosomes to be identified because of similarities in chromosome morphology of the octaploids. Results indicate that tetraploid B inermis is an allotetraploid since all chromosomes except four could be separated into identifiable pairs. Because of differences between expected and actual numbers of satellite chromosomes and chromosomes with specific C‐banding patterns, octaploid B inermis is probably not a doubled form of the tetraploid B inermis

C-Banding Analyses of Genomes

Smooth bromegrass (Bromus inermis Leyss.) has both tetraploid (2n = 28) and octaploid (2n = 56) ploidy levels that have been difficult to characterize cytogenetically because of similar chromosome morphology. Objectives of this study were to identify individual chromosomes of tetraploid and octaploid B inermis with C-banding procedures along with chromosome length and arm length ratios, develop more detailed karyotypes than those previously available, and use the karyotypes to examine the genomic relationship of tetraploid and octaploid B inermis Root tips of the plants from four tetraploid and three octaploid accessions were used to produce chromosome squash preparations for cytogenetic analysis. The tetraploid B inermis genome consisted of 12 chromosomes with a telomeric band on each arm and sixteen chromosomes with only one telomeric band on one arm. All of the chromosomes of the tetraploid form, except for four chromosomes, were identified by C-banding patterns, chromosome length, and arm length ratio. The octaploid B inermis genome consisted of four chromosomes with no C-bands, ≈14 chromosomes with two telomeric bands, and ≈38 chromosomes with only one telomeric band on either the short or long arm. The combined use of C-banding, chromosome size, and arm length ratio only enabled groups of 2, 4, 6, or 8 similar chromosomes to be identified because of similarities in chromosome morphology of the octaploids. Results indicate that tetraploid B inermis is an allotetraploid since all chromosomes except four could be separated into identifiable pairs. Because of differences between expected and actual numbers of satellite chromosomes and chromosomes with specific C-banding patterns, octaploid B inermis is probably not a doubled form of the tetraploid B inermis

Chromosome numbers of the Australian Zosteraceae

Somatic chromosome numbers of 2n = 24 are reported for all three species of Australian Zostera: Z. capricorni Aschers., Z. muelleri Irmisch ex Aschers. and Z. mucronata den Hartog and 2n = 36 for Heterozostera tasmanica (Martens ex Aschers.) den Hartog. All Australian zosteroidean species apparently have similar chromosome morphology: dot-like or rod shaped. It is suggested that the chromosome number and its morphology can be used to distinguish genera and subgenera in the Zosteraceae but not for species identification, and that speciation is not accompanied by changes of chromosome numbers.

Analysis of karyotypes and Giemsa C-banding patterns in eight species of Arachis

The karyotypes and Giemsa C-banding patterns of the chromosomes in eight species of Arachis L. have been studied. Six species are diploid with 20 chromosomes and two are tetraploid with 40 chromosomes. One diploid species (A. rigonii Krap. et Greg.) belongs to the sect. Erectoides and the rest belong to the sect. Arachis. Among the diploid species from the sect. Arachis, A. batizocoi Krap. et Greg, has a unique karyotype while others have similar karyotypes. Two tetraploid species, A. monticola Krap. et Greg, and A. hypogaea L., possess the most similar karyotypes. However, the diploid species, A. rigonii, from sect. Erectoides, has a karyotype distinguishable from those in sect. Arachis. The C-banding patterns of the chromosomes have been obtained for all the species. The centromeric bands have been found in all the chromosomes and the intercalary bands can be identified in a varied number of chromosomes among these complements. However, the telomeric bands only exist in one or two chromosomes. The comparison of banding patterns demonstrated that structural differences exist among the chromosomal complements of the species with similar chromosome morphology. The karyotype variation among the different species and interspecific relationship are discussed. It is suggested that all the diploid species with the A genome are closely related. There are close relationships between the tetraploid species and diploid species with the A or B genome within sect. Arachis. Key words: Arachis, cytology, karyotypes, Giemsa C-banding.

C-heterochromatin variation in the genus Eumigus (Orthoptera: Pamphagoidea)

Eumigus punctatus, E. monticulus and E. cucullatus all have 2n♂=19 and similar chromosome morphology, all the elements being telocentric. In E. cucullatus there are C-bands in all chromosomes, but not in E. monticulus. The possible origins of these differences and their cytotaxonomic significance are discussed.

Intrageneric divergence in DNA and heterochromatin content in ground squirrels of the genus Citellus

Until recently the comparative analysis of DNA in related eukaryotic taxa (Santiago & Rake, 1973; Straus, 1971; Vallejo-Roman et al., 1975) was carried out separately from comparative karyology by means of which the relationship between intraand interspecific karyotypic variation and heterochromatin regional variation has been shown using the chromosome C-banding techniques (Pathak et al., 1973; Prokofyeva-Belgovskaya, 1977; Lyapunova et al., 1978). Although for some species of higher organisms there are numerous data demonstrating the relationship between the repetitive DNA and constitutive heterochromatin (Yasmineh & Yunis, 1970; Pardue & Gall, 1970; Jones, 1970; Saunders et al., 1972), the comparison of chromosomal heterochromatin content variation with the variation in the number of different fractions of DNA nucleotide sequences was only made in a few studies with respect to some groups of closely related species (Yasmineh & Yunis, 1973; Mizuno & Macgregor, 1974; Narayan & Rees, 1976; Hatch et al., 1976; Ginatulina et al., 1979). Earlier we compared the data on DNA reassociation in karyologically far divergent species of the genus Ellobius widely differing in chromosome number (Ginatulin et al., 1977). In evolution, however, there are many cases of morphological divergence of species without apparent differences in chromosome number and morphology (Matthey, 1949; Vorontsov, 1958, 1966). Thus, within the ground squirrel genus (O'tellus = Spermophilus) there are species with different chromosome numbers (2n = 46, 42, 40, 38, 36, 34, 32 and 30) as well as well differentiated species with similar chromosome number (2n = 36) and morphology (Nadler, 19621966; Nadler & Sutton, 1962; Vorontsov & Lyapunova, 1969, 1970; Lyapunova, 1969; Lyapunova & Vorontsov, 1970; Matthey, 1973; Odor & Davaa, 1975). A remarkable characteristic of ground squirrels is their reproduction once a year and the onset of sexual maturity at the age of one year. This means that the geological age in years of divergence between species actually is equal to the number of generations. The genus Otellus is rather widely represented in USSR fauna. In this study Otellus species that diverged rather long ago and appear to have retained similar chromosome morphology have been used to measure the relative content and the type of C-band distribution in chromosomes, to analyse the kinetics of DNA reassociation and finally to compare the rate of intrageneric divergence in C-banded heterochromatin content and reassociation DNA characteristics.