C-banding Technique Research Articles

Initial Steps of XY Sex Chromosome Differentiation in the Armored Catfish Hypostomus albopunctatus (Siluriformes: Loricariidae) Revealed by Heterochromatin Accumulation.

In fish species, heterochromatinization is one process that could trigger sex chromosome differentiation. The present article describes a nascent XX/XY sex chromosome system evidenced by heterochromatin accumulation and microsatellite (GATA)8 in Hypostomus albopunctatus from two populations of the Paraná River basin. The specimens of H. albopunctatus from the Campo and Bossi Rivers share the same karyotype. The species exhibits 74 chromosomes (8m+14sm +16st +36a, fundamental number = 112). The C-banding technique suggests male heterogamety in H. albopunctatus, where the Y-chromosome is morphologically like the X-chromosome but differs from it for having long arms that are entirely heterochromatic. Double fluorescence in situ hybridization (FISH) with 18S and 5S rDNA probes confirmed the Ag-nucleolus organizer region sites in a single pair for both populations, and minor rDNA clusters showed interpopulational variation. FISH with the microsatellite (GATA)8 probe showed a dispersed pattern in the karyotype, accumulating these sequences of sex chromosomes of both populations. FISH with microsatellite (CGC)10 probe showed interpopulational variation. The absence of differentiated sex chromosomes in H. albopunctatus is described previously, and a new variant is documented herein where XY chromosomes can be seen in an early stage of differentiation.

Advances in the Study of Orchidinae Subtribe (Orchidaceae) Species with 40,42-Chromosomes in the Mediterranean Region

This study presents an updated analysis of cytogenetic data for several species within the 40,42-chromosome genera of the subtribe Orchidinae. The research includes insights into the distribution of heterochromatin obtained using C-banding and fluorochrome techniques. Our investigation confirmed variation in the distribution of heterochromatin and repetitive DNA sequences among species pertaining to Neotinea s.l. and Orchis s.str. These variations also potentially contribute to the diversification of these species. Cytogenetic analyses of the Neotinea group demonstrated that both H33258 and DAPI staining result in blocks of fluorescent regions on numerous chromosomes. Particular attention was paid to the cytological composition of the polyploid Neotinea commutata, focusing on its potential origin. Based on the karyological results acquired, a hypothesis concerning the origin of N. commutata is proposed. The most noteworthy revelations regard the O. mascula complex. In these species, the telomeric areas of all chromosome sets display extensive heterochromatin. Fluorochrome staining revealed telomeric blocks on many chromosomes that were not seen with Giemsa staining. This highlighted a distinct feature of O. mascula, where particularly large C-bands surrounding the centromeric regions of multiple chromosomes were found. However, in O. mascula, O. provincialis, O. pauciflora, and O. patens, C+ chromatin may not show a significant response to fluorochrome Hoechst or DAPI+ staining. The unique cytomorphological arrangement observed in the O. mascula species, unlike other members of the O. mascula complex, suggest epigenetic phenomena. Additional data are presented for the genera Dactylorhiza and Gymnadenia. A deeper understanding of the diversity of chromosomal structures among these orchids promises to shed light on the mechanisms underlying speciation, adaptation, and the remarkable diversity characteristic of the Orchidaceae family.

Molecular cytological analysis of alien introgressions in common wheat lines created by crossing of Triticum aestivum with T. dicoccoides and T. dicoccum.

Wild and domesticated emmer (ВВАА, 2n = 28) are of significant interest for expanding the genetic diversity of common wheat as sources of a high protein and microelement grain content, resistance to many biotic and abiotic factors. Particular interest in these species is also determined by their close relationship with Triticum aestivum L., which facilitates interspecific hybridization. The objective of this work was to analyze the nature of alien introgressions in hybrid lines from crossing common wheat varieties with T. dicoccoides and T. dicoccum, and to assess the effect of their genome fragments on the cytological stability of introgression lines. A C-banding technique and genotyping with SNP and SSR markers were used to determine localization and length of introgression fragments. Assessment of cytological stability was carried out on the basis of chromosome behavior in microsporogenesis. A molecular cytogenetic analysis of introgression wheat lines indicated that the inclusion of the genetic material of wild and domesticated emmer was carried out mainly in the form of whole arms or large fragments in the chromosomes of the B genome and less extended inserts in the A genome. At the same time, the highest frequency of introgressions of the emmer genome was observed in chromosomes 1A, 1B, 2B, and 3B. The analysis of the final stage of meiosis showed a high level of cytological stability in the vast majority of introgression wheat lines (meiotic index was 83.0-99.0 %), which ensures the formation of functional gametes in an amount sufficient for successful reproduction. These lines are of interest for the selection of promising material with agronomically valuable traits and their subsequent inclusion in the breeding process.

Karyotype of Sabanejewiabulgarica (Drensky, 1928) (Teleostei, Cobitidae) from the Danube Delta, Romania.

The karyotype of the freshwater fish Sabanejewiabulgarica (Drensky, 1928), from the Danube Delta, was studied by conventional Giemsa staining and the C-banding technique. The diploid chromosome number was 2n = 50. The karyotype contained 2 pairs of metacentric (the first one was much larger than the second one), 6 pairs of submetacentric and 17 pairs of subtelocentric to acrocentric chromosomes. Pericentromeric blocks of heterochromatin were revealed in most of the chromosome pairs. The karyotype phenotype of S.bulgarica was the same as found for S.balcanica from Northern Carpathian Mountains.

Türkiye'ye endemik Squalius cappadocicus Özuluğ and Freyhof, 2011'un sitogenetik özellikleri

In this study, a detailed chromosome analysis of the endemic Cappadocian Chub, Squalius cappadocicus in Melendiz Stream (Aksaray) was performed. The standard Giemsa staining, C-banding (CBG and CB-DAPI), and Ag-NOR technique were applied. The diploid chromosome number was 50; its karyotype formula was 14M + 16Sm + 10St + 10A. Heteromorphic sex chromosomes weren’t detected in the karyotype of the studied specimens. The number of all chromosomal arms (NF) was 90. In the standard C-banded and CB-DAPI karyotype of the species, dark C-bands were observed in the centromeric region of some bi-armed and acrocentric chromosomes, while slightly centromeric or pericentromeric C-bands were detected in some chromosomes. Three different active Ag-NORs, which were hemizygous, were detected in all samples examined. Two of these active NORs were detected in the bi-armed and the other in the acrocentric chromosome short arm. The Ag-NOR number of this species was evaluated as a feature that distinguishes it from other Squalius species in Türkiye.

Karyotypic variation of two populations of the small freshwater stingray Potamotrygon wallacei Carvalho, Rosa & Araújo 2016: A classical and molecular approach.

Potamotrygoninae comprises a group of Neotropical fishes with an ancient relationship with marine environments. In the last few years, 11 new Potamotrygon species were described, including Potamotrygon wallacei Carvalho, Araújo e Rosa 2016. Cytogenetic data about this species are limited to classical markers (Giemsa, C-Banding and Ag-NOR techniques), these studies highlighted a rare sexual chromosome system XX/X0 with males presenting 67 chromosomes and females 68 chromosomes. The classical analyses performed here reveled populational variation in the karyotype formula, as well as, in the heterochromatin regions. Besides the classical markers, our molecular experiments showed multiple sites for 18S rDNA sequence (including in the X chromosomes) and single sites for 5S rDNA sequence, we did not find interstitial telomeric sequences. In addition, (AC)15, (AG)15, and (CAC)15 microsatellites showed association with the several autosome pair, and the (GT)15 clutters were found in only one population. On the other hand, (GATA)4 sequence showed association with the sexual chromosomes X in all males and females analyzed. Our results showed that pericentric inversions, in addition to fusions, shaped the karyotype of P. wallacei once we found two populations with distinct karyotype formula and this could be a result of the past events recovered by our modeling experiments. Besides, here we described the association of 18S and (GATA)4 motifs with sexual chromosomes, which indicated that these sequences had a novel in the differentiation of sexual chromosomes in P. wallacei.

CLINICAL AND MOLECULAR RESULTS OF SIX CASES WITH ROBERTS SYNDROME: REVIEW OF CASES FROM TURKIYE

Objective: Roberts syndrome is a rare autosomal recessive disease characterized by limb defects, prenatal onset growth retardation, and craniofacial anomalies. We aimed to compare the clinical and molecular findings of six cases with Roberts syndrome with the previously reported patients from Turkiye and to emphasize that a definitive diagnosis can be made in the intrauterine period with cytogenetic tests in the early period without the need to wait for molecular test results. Materials and Methods: Six cases, diagnosed with Roberts syndrome, in our outpatient clinic of Istanbul University, Istanbul Faculty of Medicine, Medical Genetics Department between 2015-2021, were included in the study. The family history, clinical information, and cytogenetic and molecular findings of the patients were retrospectively reviewed and compared with the cases reported from Turkiye in the literature. G and C-banding techniques and Sanger sequencing of the ESCO2 gene were performed. Results: Pathogenic variants in homozygous in four and compound heterozygous in two patients in the ESCO2 gene were identified. Compound heterozygous c.[417dup];[1131+1G>A] (p.[(Pro140Thrfs*8)];[(?)]) in case 1, and c.[1111dup];[760del] (p. [(Thr371Asnfs*32)];[(Thr254Leufs*13)]) in case 6, homozygous c.1131+1G>A (p.(?)) in case 2, case 3 and case 5, and homozygous c.1111dup (p.(Thr371Asnfs*32)) in case 4 were detected. The variants reported in our case series were previously associated with the disease. The first demonstration of the c.760del in a Turkish case contributed to the genetic association of this pathogenic variants with Roberts syndrome Although all the previously reported patients were homozygous, we have detected two patients with compound heterozygous pathogenic alterations from Turkiye indicating that the disease should also be considered in families with no consanguinity.

Karyotypes and ZZ/ZW Sex Chromosome System of Endemic Squalius recurvirostris (Leuciscinae, Cyprinidae) in Turkey

In this study, detailed cytogenetic properties of the endemic Akşehir chub, Squalius recurvirostris, distributed in the basin of the Ilgın (Çavuşçu) Lake basin was investigated by applying the standard Giemsa staining, C-banding and Ag-NOR technique. Diploid chromosome number is (2n) 50. A pair of heteromorphic chromosomes was detected in the karyotype in females. However, this difference was not observed in males. Therefore, it was determined that the heteromorphic chromosome pair in females were ZZ/ZW sex chromosomes. The Z chromosome in females is large acrocentric, and the W chromosome is medium-sized submeta/subtelocentric. The number of all chromosomal arms (NF) is 90, and the fundamental number of autosomal arms (NFa) is 88 in the karyotyped of the individuals studied. Some bi-armed and acrocentric chromosomes have centromeric C-bands in the chromosome set. The slightly centromeric or pericentromeric C-bands are observed in some chromosomes, while other chromosome pairs are C-negative. In the individuals studied two active NORs were detected. Both of these NORs were hemizygous and associated with a large C-heterochromatin region. One of the NORs was detected on the entire long arm of the submetacentric chromosome pair and the other on the entire short arm of another submetacentric chromosome pair.

A Perspective of Molecular Cytogenomics, Toxicology, and Epigenetics for the Increase of Heterochromatic Regions and Retrotransposable Elements in Tambaqui (Colossoma macropomum) Exposed to the Parasiticide Trichlorfon.

Simple SummaryThe aim of the present study was to evaluate the Trichlorfon effects on the retrotransposable elements in tambaqui (Colossoma macropomum) genome, which is a highly popular and well-known fish in the Amazon with a large reproduction number mediated by pisciculture. Thereby, tambaqui specimens were submitted to two different Trichlorfon concentrations (30% and 50% of LC50–96 h) under experimental conditions. The retrotransposons were analyzed using the FISH technique and the heterochromatin standard with the C-band technique. The retrotransposons studied presented a dispersed distribution profile in the tambaqui karyotype with Rex3 being more prominent than the others, showing the greatest increase in markings. Furthermore, the heterochromatin profile showed that these retrotransposons can be found in the heterochromatic portions of the chromosomes. Thus, it was observed that Trichlorfon has an activation mechanism for these retroelements, especially Rex3.Rex retroelements are the best-known transposable elements class and are broadly distributed through fish and also individual genomes, playing an important role in their evolutionary dynamics. Several agents can stress these elements; among them, there are some parasitic compounds such as the organochlorophosphate Trichlorfon. Consequently, knowing that the organochlorophosphate Trichlorfon is indiscriminately used as an antiparasitic in aquaculture, the current study aimed to analyze the effects of this compound on the activation of the Transposable Elements (TEs) Rex1, Rex3, and Rex6 and the structure of heterochromatin in the mitotic chromosomes of the tambaqui (Colossoma macropomum). For this, two concentrations of the pesticide were used: 30% (0.261 mg/L) and 50% (0.435 mg/L) of the recommended LC50–96 h concentration (0.87 mg/L) for this fish species. The results revealed a dispersed distribution for Rex1 and Rex6 retroelements. Rex3 showed an increase in both marking intensity and distribution, as well as enhanced chromosomal heterochromatinization. This probably happened by the mediation of epigenetic adaptive mechanisms, causing the retroelement mobilization to be repressed. However, this behavior was most evident when Trichlorfon concentrations and exposure times were the greatest, reflecting the genetic flexibility necessary for this species to successfully adapt to environmental changes.

Cytogenetic Analysis of Alburnus escherichii (Teleostei: Leuciscidae) in Turkey

In this study, cytogenetic properties of A. escherichii were investigated using standard Giemsa staining, C-banding, and Ag-NOR staining techniques. The karyotype of Sakarya bleak, the diploid chromosome number was 2n = 50, consists of six pairs of metacentric, 12 pairs of submetacentric, and seven pairs of acrocentric autosomes (NF=86). No morphologically distinguishable heteromorphic sex chromosomes were detected in the karyotype. While most autosomes had centromeric and pericentromeric C-heterochromatin (some chromosomes slightly) blocks, the other autosomal pairs were C-negative. Also, the short arm of the eleventh submetacentric chromosome pair was entirely C-positive. The nucleolar organizer regions were localized in medium-sized submetacentric autosomal pairs. Active NORs associated with the C-heterochromatin were observed in the whole of the short arm of the eleventh chromosome pair, and their active NORs were homomorphic. The banded karyotypes of A. escherichii were reported in this study for the first time. Significant findings obtained in this research may contribute to cytotaxonomy of Alburnus species in Anatolian and Europe.

A DAPI-Based Modified C-banding Technique for a Rapid Achieving High Photographic Contrast of Centromeres on Chromosomes.

Many chromosome assays rely on the quantification of chromosome abnormalities in cells, and one important abnormality is the existence of more than one centromere for each chromosome. The quantification of such abnormalities has been studied before. However, this process is labor-intensive and time consuming. Thus, this assay is challenging for ex-laboratory applications, where speed is required. We present a visualization method that uses a cheap stain-DAPI, long (e.g., high-resolution) chromosomes and our modified C-banding method for labeling chromosomes. The labeled chromosomes can then be easily seen with a conventional and readily available fluorescence microscopy system. This method achieves an acceleration of the detection of the presence of constitutive heterochromatin in chromosomal centromeres by more than 10 times, to ~2 h, in Human lymphocyte cells and in cells of the human Jurkat line. This new procedure will ultimately provide an easier and cheaper alternative to FISH/PNA probes, or the classic Giemsa staining method. Simplification and reduction in time of the overall procedure will enable the utilization of centromere-counting assays in laboratory and ex-laboratory applications, including in emergency response.

Sex chromosomes in the Vizcacheras' White-lipped frog, Leptodactylus bufonius (Anura, Leptodactylidae).

Cytogenetic analyses were performed on specimens of Leptodactylus bufonius from different localities in Argentina. Mitotic chromosomes were studied with Giemsa and differential staining techniques (Ag-NOR, C-banding, and CMA3/DAPI) and fluorescence in situ hybridization with the 18S DNAr probe. All specimens showed karyotypes with 2n = 2x = 22 and FN = 44. Secondary constrictions were present in the long arm of chromosome pair 8, coincident with Ag-NOR and hybridization signals of the 18S DNAr probe. The C-banding technique evidenced an important amount of heterochromatin with a sex-linked pericentromeric band in the short arm of chromosome pair 4. This heterochromatic band was heteromorphic in males but present in both homologues of females, and it was CMA3 positive (DAPI negative) at fluorescence staining. The occurrence of heteromorphic XY sex chromosomes in L. bufonius is the second known case in Leptodactylus and the fifth within the speciose family Leptodactylidae.

Cytogenetic characterization of Ameivula ocellifera (Spix, 1825) (Squamata, Teiidae) from the brazilian northeast

Ameivula is as a new genus of Teiidae family that emerged after extensive revision of species that comprised the former complex of species called Cnemidophorus group. Its species has a wide distribution from the northeast of Brazil to northern Argentina. Cytogenetic studies in the Teiidae family have shown that karyotypical data are important tools in phylogenetic and systematic studies within this group allowing to determine the position of species in the family. Thus, this study aimed to describe the karyotype of Ameivula ocellifera (Spix, 1825) from Picos, Piauí state in the Brazilian Northeast. Specimens were collected from August 2014 to October 2015 using interception traps and pitfalls, mounted randomly along the Caatinga area. The animals were collected and transported to Federal Institute of Piauí, campus Picos, where was carried out all laboratory procedures. Individuals analyzed showed a diploid number of 2n = 50 for both sexes, with karyotype composed by 30 macrochromosomes and 20 microchromosomes of telocentric and subtelocentric types. There were no heteromorphic sex chromosomes in the studied specimens. C-band technique evidenced the heterochromatic blocks in pericentromeric and telomeric regions of chromosomes. The nucleolar organizing regions appeared as a simple unit located at the terminal portion of the long arm of chromosomal pair number 5. The chromosomal characteristics of A. ocellifera analyzed do not show divergences regarding individuals from other regions. However, the nucleolar organizing regions seems to be a good chromosomal marker that permits to distinguish the species already studied.

Overview on Karyotype Stasis in Atlantic Grunts (Eupercaria, Haemulidae) and the Evolutionary Extensions for Other Marine Fish Groups

Karyotype stasis, characterized by the absence of changes in chromosome number, genomic structure, and ploidy, is a recurrent condition in many biological groups, such as plants, amphibians, birds, and fishes. In fishes, the Percomorpha clade (>17,000 species), especially, its largest series, Eupercaria (>6,000 species and 161 families), shows an extensively shared karyotype with 2n=48 acrocentrics; the phylogenetic extension in this series is still unknown. Haemulidae (grunts) .a bounds the zoogeographic marine provinces of the Caribbean and Brazil, has a variable effect on the gene flow in diverse fish groups. Geographically, this barrier is located inside the distribution area of several fish species of Atlantic, allowing the examination of its role on the eventual karyotype differentiations in the populations of grunts. In this sense, cytogenomic analyses were carried out in eight haemulid species by conventional cytogenetic approaches (Giemsa staining, C-banding, and Ag-NORs technique), staining with base-specific fluorochromes, and two-color fluorescent in situ hybridization (FISH) with 5S and 18S rDNA probes. Additionally, we performed an exhaustive survey on the cytogenetic data of species from the Eupercaria series to assess the general context of karyotype divergences. Haemulid species and populations showed a pronounced sharing of karyotypes with 2n=48a, simple NORs, and reduced centromeric heterochromatin, apart from recurrent patterns of ribosomal 5S and 18S rDNA sites. Karyotype similarities persisted at intra- and congeneric levels in the Haemulidae family, indicating accentuated syntenic conservatism through large divergence periods. Stable karyotype patterns were extensively present in the majority of members from Eupercaria (88% of the clades in this series). These results indicate that karyotype stasis, which is found in a large spectrum of marine fishes, is a multifactorial process in terms of phylogenetic, biological, and biogeographic contexts.

C-banding and AgNOR-staining were still effective complementary methods to indentify chromosomal heteromorphisms and some structural abnormalities in prenatal diagnosis

BackgroundIn prenatal diagnosis, CMA has begun to emerge as a favorable alternative to karyotype analysis, but it could not identify balanced translocations, triploidies, inversion and heteromorphisms. Therefore, conventional cytogenetic and specific staining methods still play an important role in the work-up of chromosome anomaly. This study investigated the application of C-banding and AgNOR-staining techniques in prenatal diagnosis of chromosomal heteromorphisms and some structure abnormalities.ResultsAmong the 2970 samples, the incidence of chromosomal heteromorphisms was 8.79% (261/2970). The most frequent was found to be chromosome Y (2.93%, 87/2970), followed by chromosome 1 (1.65 %, 49/2970), 9 (1.52 %, 45/2970), 22 (0.77 %, 23/2970) and 15 (0.64 %, 19/2970). We compared the incidence of chromosomal heteromorphisms between recurrent spontaneous abortion (RSA) group and control group. The frequency of autosomal hetermorphisms in RSA group was 7.63% higher than that in control group (5.78%), while the frequency of Y chromosomal heteromorphisms was 4.76% lower than that in control group (5.71%). Here we summarized 4 representative cases, inv (1) (p12q24), psu dic (4;17) (p16.3;p13.3), r(X)(p11; q21) and an isodicentric bisatellited chromosome to illustrate the application of C-banding or AgNOR-staining, CMA or NGS was performed to detect CNVs if necessary.ConclusionsThis study indicated that C-banding and AgNOR-staining were still effective complementary methods to identify chromosomal heteromorphisms and marker chromosomes or some structural rearrangements involving the centromere or acrocentric chromosomes. Our results suggested that there was no evidence for an association between chromosomal heteromorphisms and infertility or recurrent spontaneous abortions. Undoubtedly, sometimes we needed to combine the results of CMA or CNV-seq to comprehensively reflect the structure and aberration of chromosome segments. Thus, accurate karyotype reports and genetic counseling could be provided.

Karyotypic description of the stingless bee Meliponaquinquefasciata Lepeletier, 1836 (Hymenoptera, Meliponini) with emphasis on the presence of B chromosomes.

Stingless bees are distributed widely in the tropics, where they are major pollinators of several plant species. In this study, the karyotype of Meliponaquinquefasciata Lepeletier, 1836 was analysed, with emphasis on the presence of B chromosomes. Post-defecating larvae were analysed using Giemsa staining, the C-banding technique, sequential staining with fluorochromes, and FISH. The chromosome number ranged from 2n = 18 to 22 (females) and from n = 9 to 13 (males) due to the presence of 0–4 B chromosomes. This result demonstrates that M.quinquefasciata has the same chromosomal number as other Melipona Illiger, 1806 species. Considering the A complement, heterochromatin was located only in the pericentromeric region of pair 1. Staining with chromomycin A3 (CMA3) and labelling with rDNA probe, indicated that this region corresponded to the nucleolus organising region. The B chromosomes of M.quinquefasciata could be found in individuals from different localities, they were completely heterochromatic (C-banding) and uniformly stained by 4’,6-diamidino-2-phenylindole (DAPI). Variations in the number of B chromosomes were detected between cells of the same individual, between individuals of the same colony, and between colonies from different localities.

Distinct classical and molecular cytogenetics of Astyanax marionae and A. fasciatus (Characiformes: Characidae): a comparative study of the organization of heterochromatin and repetitive genes.

Genus Astyanax is well distributed in Neotropical freshwater environments and its taxonomic position is uncertain, as is the case with other Characidae genera allocated in the group incertae sedis. This study aimed to analyse the karyotype of different populations of Astyanax fasciatus (Corumbataí River basin) using Giemsa staining, C-band technique, and fluorescence in situ hybridization for the H3 histone and 5S rRNA genes, in addition we describe for the first time the chromosomal organization of H3 histone and 5S rRNAgenes in A. marionae (ParaguayRiver basin). Chromosomes of three A. fasciatus populations were analysed (two with 2n = 50 and one with 2n = 48) and the heterochromatin was organized in two forms (blocks with blurred boundaries and distinct blocks). H3 histone and 5S rRNA genes were observed in all the three populations of A. fasciatus on two chromosome pairs (one metacentric chromosome showing H3 histone and 5S rRNA gene clusters). In A. marionae (2n = 48), H3 histone and 5S rRNA genes were observed in one acrocentric chromosome pair (different pairs). Further, differences between karyotypes and heterochromatin, as well as the chromosomal organization of H3 histone and 5S rRNA genes in Astyanax species, focussing on chromosome evolution in the group are discussed.

Use of C-banding for identifying radiation induced micronuclei

Differentiation of micronuclei (MN) caused by ionizing radiation from those caused by chemicals is a crucial step for managing treatment of individuals exposed to radiation. MN in binucleated lymphocytes in peripheral blood are widely used as biomarkers for estimating dose of radiation, but they are not specific for ionizing radiation. MN induced by ionizing radiation originate predominantly as a result of chromosome breaks (clastogenic action), whereas MN caused by chemical agents are derived from the loss of entire chromosomes (aneugenic action). C-banding highlights centromeres, which might make it possible to distinguish radiation induced MN, i.e., as a byproduct of acentric fragments, from those caused by the loss of entire chromosomes. To test the use of C-banding for identifying radiation induced MN, a blood sample from a healthy donor was irradiated with 3 Gy of Co-60 gamma rays and cultured. Cells were harvested and dropped onto slides, divided into a group stained directly with Giemsa and another processed for C banding, then stained with Giemsa. The frequency of MN in 500 binucleated cells was scored for each method. In preparations stained with Giemsa directly, the MN appeared as uniformly stained structures, whereas after C banding, some MN exhibited darker regions corresponding to centromeres that indicated that they were not derived from acentric fragments. The C-banding technique enables differentiation of MN from acentric chromosomal material. This distinction is useful for improving the specificity of the MN assay as a biomarker for ionizing radiation.

Cranial and chromosomal geographic variation in manatees (Mammalia: Sirenia: Trichechidae) with the description of the Antillean manatee karyotype in Brazil

We employed landmark-based 3D geometric morphometrics to assess cranial size and shape diversification in Trichechus manatus and T. inunguis to compare it with patterns among all manatee taxa (T. manatus latirostris, T. m. manatus, T. inunguis and T. senegalensis), and to analyse geographic variation within American manatee populations, using a sample of 189 skulls. Chromosome G- and C-banding techniques were performed in T. m. manatus from Brazil. All taxa were statistically discriminated by skull shape. Trichechus m. manatus and T. m. latirostris have larger skulls than T. inunguis. A morphological discontinuity was noted within T. m. manatus, with the Brazilian population south of the Amazon discriminated from the T. m. manatus Caribbean and T. m. latirostris USA populations. Specimens from Suriname and Guyana had a skull shape more similar to the one from the Caribbean population. The Brazil Antillean manatee population exhibited morphological differences similar in magnitude to those found between the Amazonian and African species. Additionally, structural chromosome differences were detected between that population (chromosome pair 4 is metacentric and 10 is submetacentric) and manatees from Puerto Rico and Florida. Based on such morphological discontinuity and chromosomal divergence, we hypothesize that the Amazon River mouth may be acting as a reproductive barrier for the T. m. manatus population in Brazil, thus indicating that its taxonomic status and conservation strategies need an urgent reassessment.

A C-banded karyotype of mitotic chromosomes in diploid purple coneflower (Echinacea purpurea L.).

BackgroundAneuploid ermpglasm is an important resource for genetic studies and identification of individual chromosomes in the cells of the aneuploid is an important step. The karyotype has already been established for purple coneflower (Echinacea purpurea L.), but due to the high similarity in the morphology of several pairs of chromosomes in this species, it cannot be used to identify individual chromosomes in its own complement. The objectives of this study are to develop and evaluate the Giemsa C-banding technique for the purpose of identifying the individual chromosomes in Echinacea purpurea.ResultsThe established karyotype with C-bands showed that all the 11 pairs of chromosomes possessed centromeric bands. Telomeric bands appeared most frequently in almost all the chromosomes with only two exceptions, the short arm of the chromosome 9 and the long arm of the chromosome 10. Intercalary bands were found mainly in the long arm of some chromosomes with only two exceptions, the chromosomes 1 and 2 that had intercalary bands on both arms. The chromosome 4 was the only chromosome where intercalary bands were absent.ConclusionsChromosomes in E. purpurea could be stained with Giemsa to bear C-bands. By classifying the chromosomes into groups and judging the C-bands, each chromosome could be identified. The methods established in this study might be used for the identification of chromosome constitution in aneuploid E. purpurea created in a breeding program.