Secondary Constriction Of Chromosome Research Articles

Karyological Study of Siberian Larch Species Larix sibirica and Larix gmelinii in Taimyr

A comparative study of karyotypes of two Siberian species of larch—L. sibirica and L. gmelinii—growing in the zone of forest-tundra on the Taimyr Peninsula was carried out. The number of chromosomes has been analyzed and the increase in chromosomal instability in larches in forest-tundra conditions has been shown. The size and morphology of chromosomes and the localization and frequency of secondary constrictions in chromosomes of L. sibirica and L. gmelinii were estimated. The parameters of chromosomes in polyploid cells of L. gmelinii were studied. The asymmetry of karyotypes of L. sibirica and L. gmelinii was analyzed. The spectrum and frequency of chromosome rearrangements in L. sibirica and L. gmelinii were studied. Using the data of the karyological analysis, the issues of differentiation and adaptation of the investigated larch species in Taimyr are discussed.

Development of caryological and molecular-genetic investigations of wetland and dryland populations of conifers

Aim. On the basis of studies which carried out by various authors, regularities of karyotypic and genetic divergence of populations of conifers growing in wetlands and dry lands are analyzed. Methods. The karyological and molecular-genetic methods of analysis are used. Results. Data are obtained on possible ways of evolution of karyotypes, consisting in changes in the number of chromosomes, the size and morphology of chromosomes, the number of secondary constrictions in chromosomes, the spectrum of chromosome rearrangements, and the frequency of their occurrence, distinguishing wetland populations of conifers species from dry land ones. With the help of isozyme markers and markers of nuclear and cytoplasmic genomes differences in the genetic structure of conifers populations from wetlands and dry lands are revealed. Conclusions. The genotypic structure of conifers species in wetlands and dry lands, caused by different vector of natural selection in contrasting ecological conditions of growth, differs significantly, and their karyotypic and genetic differentiation corresponds to the level of populations and groups of populations.
 Keywords: populations of conifers, wetlands, dry lands, karyological and molecular-genetic markers.

Ecotopic differentiation of yellow-anthered and red-anthered forms of scots pine by karyological traits and nuclear DNA content

A comparative study of yellow-anthered and red-anthered forms of Scots pine, growing in hydrothermally contrasting bog and upland ecotopes, was performed by karyological traits and nuclear DNA content. Some differences were revealed between yellow-anthered and red-anthered forms of pine as components of intraspecific diversity in'the frequency of occurrence of violations in the number of chromosomes, chromosome sizes (total length of diploid set, absolute and relative lengths), the centromeric index, the localization of secondary constrictions in chromosomes, and the amount of DNA.

Chromosomal localization of the 18S-28S and 5S rRNA genes and (TTAGGG)n sequences of butterfly lizards (Leiolepis belliana belliana and Leiolepis boehmei, Agamidae, Squamata)

Chromosomal mapping of the butterfly lizards Leiolepis belliana belliana and L. boehmei was done using the 18S-28S and 5S rRNA genes and telomeric (TTAGGG)n sequences. The karyotype of L. b. belliana was 2n = 36, whereas that of L. boehmei was 2n = 34. The 18S-28S rRNA genes were located at the secondary constriction of the long arm of chromosome 1, while the 5S rRNA genes were found in the pericentromeric region of chromosome 6 in both species. Hybridization signals for the (TTAGGG)n sequence were observed at the telomeric ends of all chromosomes, as well as interstitially at the same position as the 18S-28S rRNA genes in L. boehmei. This finding suggests that in L. boehmei telomere-to-telomere fusion probably occurred between chromosome 1 and a microchromosome where the 18S-28S rRNA genes were located or, alternatively, at the secondary constriction of chromosome 1. The absence of telomeric sequence signals in chromosome 1 of L. b. belliana suggested that its chromosomes may have only a few copies of the (TTAGGG)n sequence or that there may have been a gradual loss of the repeat sequences during chromosomal evolution.

Different patterns of chromosome exchange induced by methyl-metanesulphonate and mitomycin C in human cells.

A comparison between 72 chromosome exchanges in human lymphocytes induced by methyl-metanesulphonate (MMS) and 84 exchanges induced by mitomycin C (MC) revealed a different pattern. The prevalence of attenuations, lateral extensions and exchanges in the secondary constrictions of chromosomes 1, 9, and 16 in the MC-treated material is not found with MMS. This may be due to a specific gathering effect of MC upon this particular chromatin. Both materials show a prevalence of C-band exchange, which may be due to repetitious DNA.

Distribution of mitomycin C induced breaks on human chromosomes.

Mitomycin C induced chromosome aberrations were analysed in cultured human lymphocytes by the quinacrine mustard chromosome banding technique. There was an overrepresentation of interchange aberrations involving the C-bands of homologous chromosomes, and especially the secondary constrictions of chromosomes 1, 9 and 16. Interchanges involving other bands rarely occurred between homologous chromosomes. These findings indicate that the C-bands are aggregated in the cell and/or that such an aggregation is induced by mitomycin C. The chromatid and chromosome breaks appeared to be located preferentially in the R-bands.

Karyological analysis of larch species from Siberia and the far east of Russia

Data on karyological studies of five larch species ‐ Larix sibirica Ledeb., L. gmelinii (Rupr.) Rupr., L. cajanderi Mayr, L. ochotensis Kolesn., L. × amurensis Kolesn. in different parts of area are presented. Karyotype of Larix (2n = 24) consists of 24 chromosomes (2n = 24) and includes 6 pairs of symmetric (metacentric) and 6 pairs of asymmetric (submeta‐ and intercentric) chromosomes. Except A‐chromo‐somes some populations have B‐chromosome (2n = 24+1B). The number of genome and chromosome mutations including polyploid and aneuploid cells, ring and dicentric chromosomes, fragments was higher in extreme conditions. Based on the number of secondary constrictions in chromosomes the genus Larix was subdivided into some karyotypic groups. Species with one pair of nucleolar chromosomes consist of the first group. Larix taxa with two pairs of nucleolar chromosomes consist of the second group. Many species have three or more pairs of chromosomes with secondary constrictions and form the third group.

Molecular Cytogenetic Analysis of Four Larix Species by Bicolor Fluorescence In Situ Hybridization and DAPI Banding

Mitotic metaphase complements of four Eurasian Larix species, L. gmelinii, L. principis‐rupprechtii, L. kaempfeeri, and L. olgensis, were analyzed by bicolor fluorescence in situ hybridization (FISH) with 25S and 5S rDNA probes as well as DAPI banding. The four species were all diploids with the common chromosome number of 2n=24. All of the 25S rDNA clusters were located in the secondary constrictions of chromosomes, but the number of their sites varied among species. In L. kaempfeeri and L. olgensis, a pair of 25S rDNA loci were found on each of two large metacentric chromosome pairs, while in L. gmelinii and L. principis‐rupprechtii, another two loci were present on the long arms of one pair of submetacentric chromosomes. The 5S rDNA FISH pattern was less variable, with only one site commonly observed in each species. These loci occurred on a pair of large metacentrics that also harbored 25S rDNA on different arms. Bright, fluorescent DAPI bands were positioned adjacent to the centromeres of all but one chromosome pair of L. kaempfeeri and L. olgensis and adjacent to the centromeres of all but two chromosome pairs of L. gmelinii and L. principis‐rupprechtii. However, these bands showed obvious differences in intensity between the species, and together with the interspecific variation of 25S rDNA FISH patterns, they provide preliminary molecular cytogenetic evidence for phylogenetic study of these Larix species.

Comparative Karyotype Analysis of Grasshoppers in the Genus Oxya (Orthoptera, Catantopidae) by Differential Staining Techniques

The chromosomes of 4 species of grasshopper in the genus Oxya were analyzed by conventional and five differential-staining methods. All 4 species had a chromosome complement of 2n=22+XX(female)/XO(male), with very similar karyotypes. Both O. hyla intricata and O. japonica japonica had acrocentric chromosomes with minute short arms, while the chromosomes of O. chinensis formosana and O. yezoensis were almost all telocentric. In all 4 species, a secondary constriction (SC) was detected at a proximal site in chromosome 8, which had the same staining properties (positive for C- and CMA-banding; negative for G- and QM-banding) in all 4 species. Our C-banding analysis revealed that the short arms of O. hyla intricata and O. japonica japonica consisted of C-heterochromatin. The 4 species yielded species-specific patterns of C-bands, and there appeared to be a close relationship between O. chinensis formosana and O. yezoensis, as suggested by the polymorphism of the distal C-bands of chromosome 2. In all 4 species of Oxya, Ag-NORs were detected on the centromeric regions of all the chromosomes, but not detected on the SC of chromosome 8. The karyosystematic relationships among the 4 species are discussed on the basis of the results of differential staining.

NOR-associated heterochromatin of pepper chromosomes stained with acridine orange

Abstract Acridine orange is a non-specific fluorescent dye which binds to DNA mainly by intercalating between base pairs. In human and animal cytogenetics this dye has been extensively utilized to show reverse banding pattern (RFA). Considering the absence of G- and R-bands in plant chromosomes, the use of acridine orange after pretreatment in C- banding protocols has been applied for detecting heterochromatic segments associated with the nucleolus organizing regions (NORs). Therefore, the RFA technique, as applied to higher vertebrates, was used in this work for pepper (Capsicum annuum L.) chromosomes to detect NOR-associated heterochromatic segments. For the Capsicum genus, other methods described in the literature have led to conflicting NOR positions results. Bands emitting yellowish-green fluorescence were located in the secondary constriction of chromosome 5 and flanking the NOR of chromosome 11 of pepper. The maize chromosome 6, used as a known NOR position standard, showed similar results. Additio...

Chromosome mapping of Xenopus tropicalis using the G- and Ag-bands: tandem duplication and polyploidization of larvae heads.

Developmental cytogenetic analyses of Xenopus tropicalis larvae from two origins were performed on stage 27-34 heads treated with colchicine. Standard G-band karyotyping using trypsin and chromosome mapping of 184 bands were examined. Although the main karyotype was 2n = 20, polyploidy (3n = 30 or 4n = 40) and aneuploidy were detected in each individual treated with colchicine, even those treated for only 1 h. The percentage of polyploid karyotypes was 10-20% across the total of measured metaphases. The mean mitotic index was 0.10. Chromosomal breaks and exchanges were detected at the secondary constriction of chromosomes 5 or 6. Ag-band detection showed clearly positive staining at the secondary constriction of chromosome 5, which corresponds to the nucleolar organizer region. Tandem duplication of negative G-bands at the secondary constriction of chromosome 6 and the short arm of chromosome 10 was suggested by this study. X. tropicalis thus provides a good model to study the mechanism and effects of chromosomal abnormalities, gene mapping and tissue specific gene expression in the developmental process.

Karyotype analysis ofLilium longiflorumandLilium rubellumby chromosome banding and fluorescence in situ hybridisation

Detailed karyotypes of Lilium longiflorum and L. rubellum were constructed on the basis of chromosome arm lengths, C-banding, AgNO3 staining, and PI-DAPI banding, together with fluorescence in situ hybridisation (FISH) with the 5S and 45S rDNA sequences as probes. The C-banding patterns that were obtained with the standard BSG technique revealed only few minor bands on heterologous positions of the L. longiflorum and L. rubellum chromosomes. FISH of the 5S and 45S rDNA probes on L. longiflorum metaphase complements showed overlapping signals at proximal positions of the short arms of chromosomes 4 and 7, a single 5S rDNA signal on the secondary constriction of chromosome 3, and one 45S rDNA signal adjacent to the 5S rDNA signal on the subdistal part of the long arm of chromosome 3. In L. rubellum, we observed co-localisation of the 5S and 45S rDNA sequences on the short arm of chromosomes 2 and 4 and on the long arms of chromosomes 2 and 3, and two adjacent bands on chromosome 12. Silver staining (Ag-NOR) of the nucleoli and NORs in L. longiflorum and L. rubellum yielded a highly variable number of signals in interphase nuclei and only a few faint silver deposits on the NORs of mitotic metaphase chromosomes. In preparations stained with PI and DAPI, we observed both red- and blue-fluorescing bands at different positions on the L. longiflorum and L. rubellum chromosomes. The red-fluorescing or so-called reverse PI-DAPI bands always coincided with rDNA sites, whereas the blue-fluorescing DAPI bands corresponded to C-bands. Based on these techniques, we could identify most of chromosomes of the L. longiflorum and L. rubellum karyotypes.

Heterochromatic banding pattern in two Brazilian populations of Aedes aegypti.

We analysed samples of Aedes aegypti from São José do Rio Preto and Franca (Brazil) by C-banding and Ag-banding staining techniques. C-banding pattern of Ae. aegypti from São José do Rio Preto examined in metaphase cells differed from Franca. The chromosomes 2, 3 and X showed centromeric C-bands in both populations, but a slightly stained centromeric band in the Y chromosome was observed only in São José do Rio Preto. In addition, the X chromosome in both populations and the Y chromosome of all individuals from São José do Rio Preto showed an intercalary band on one of the arms that was absent in Franca. An intercalary, new band, lying on the secondary constriction of chromosome 3 was also present in mosquitoes of both populations. The comparison of the present data with data in the literature for Ae. aegypti from other regions of the world showed that they differ as to the banding pattern of sex chromosomes and the now described intercalary band in chromosome 3. The observations suggested that the heterochromatic regions of all chromosomes are associated to constitute a single C-banded body in interphase cells. Ag-banding technique stained the centromeric regions of all chromosomes (including the Y) and the intercalary C-band region of the X chromosome in both populations. As Ae. aegypti populations are widespread in a great part of the world, the banding pattern variations indicate environmental interactions and may reveal both the chromosome evolutionary patterns in this species and the variations that may interfere with its vector activity.

Analysis of active nucleolus organizing regions inCapsicum (Solanaceae) by silver staining

Nucleolar activity of 22 samples belonging to nine diploid species of Capsicum was analyzed in somatic metaphases and interphase nuclei. They are: C, chacoënse, C. parvifolium, C. frutescens, C. chinense, C. annuum var. annuum, C. baccatum var. pendulum, C. pubescens, all with 2n = 24, and C. mirabile var. mirabile and C. campylopodium with 2n = 26. Silver staining was applied for the first time in Capsicum, providing useful markers for chromosome identification in combination with other banding techniques already employed in the genus. From two to eight AgNORs (silver‐stained nucleolus organizing regions) were found in the diploid complement of the taxa studied. Nucleolar organizers are located at secondary constrictions of chromosomes which are conventionally stained or banded (C‐banding or fluorochrome banding). Polymorphism of AgNORs and attached satellites often occurs. Nucleoli are usually fused to a variable extent. Number and position of active rDNA loci are variable not only between but also within species and populations. Homologies in position of NORs between species were established. The data obtained are related to previous conclusions on phylogenetic relationships in Capsicum. Possible trends of karyotype evolution concerning nucleolar organizers are discussed, and four NORs in the diploid complement (on chromosome pairs #1 [m] and #12 [st]) are regarded as the plesiomorphic condition.

Analysis of Active Nucleolus Organizing Regions in Capsicum (Solanaceae) by Silver Staining

Nucleolar activity of 22 samples belonging to nine diploid species of Capsicum was analyzed in somatic metaphases and interphase nuclei. They are: C, chacoënse, C. parvifolium, C. frutescens, C. chinense, C. annuum var. annuum, C. baccatum var. pendulum, C. pubescens, all with 2n = 24, and C. mirabile var. mirabile and C. campylopodium with 2n = 26. Silver staining was applied for the first time in Capsicum, providing useful markers for chromosome identification in combination with other banding techniques already employed in the genus. From two to eight AgNORs (silver-stained nucleolus organizing regions) were found in the diploid complement of the taxa studied. Nucleolar organizers are located at secondary constrictions of chromosomes which are conventionally stained or banded (C-banding or fluorochrome banding). Polymorphism of AgNORs and attached satellites often occurs. Nucleoli are usually fused to a variable extent. Number and position of active rDNA loci are variable not only between but also within species and populations. Homologies in position of NORs between species were established. The data obtained are related to previous conclusions on phylogenetic relationships in Capsicum. Possible trends of karyotype evolution concerning nucleolar organizers are discussed, and four NORs in the diploid complement (on chromosome pairs #1 [m] and #12 [st]) are regarded as the plesiomorphic condition.

Human autoantibody to RNA polymerase I transcription factor hUBF. Molecular identity of nucleolus organizer region autoantigen NOR-90 and ribosomal RNA transcription upstream binding factor.

In dividing eukaryotic cells, nucleoli disperse before mitosis and reform in daughter cells at sites of ribosomal RNA (rRNA) gene clusters that are at the secondary constrictions of chromosomes, called nucleolus organizer regions (NORs). In this study, cDNA clones for a NOR autoantigen (NOR-90) were selected using a specific human autoantibody probe and were subsequently identified to encode an alternative form of the reported human upstream binding factor (hUBF). Results from immunoprecipitation showed that anti-NOR-90 antibodies recognized both forms of hUBF/NOR-90. Our data therefore showed that UBF, a critical factor in the regulation of rRNA transcription, was tightly bound to NOR during mitosis even when rRNA synthesis was thought to be minimal. Furthermore, we identified a nucleolar transcription factor as a novel target for human autoimmune response.

Translocation t(1;17)(q12;q25) with a clinical picture like of a proximal deletion of 1q: identification by in situ hybridization with chromosome 1-specific satellite DNA probes

The authors report a case of a balanced 1;17 translocation with breakpoints located in the secondary constriction of chromosome 1. This translocation is associated with pathological symptoms similar to those observed following a proximal deletion of 1q. We request contact with colleques who have observed similar, or related, cases of translocation with breakpoints in heterochromatic regions of human chromosomes.

Position-specific effects in the mutagenic action of mitomycin C on the chromosomes of Hordeum vulgare L.

The mutagenic action of mitomycin C (MMC) on the chromosomes of two reconstructed karyotypes of barley was studied. MMC-induced chromatid aberrations were found to be distributed non-randomly along the chromosomes. The regions situated next to the secondary constrictions of chromosomes 6 and 7 appeared to be clearly pronounced aberration "hot spots". In these segments, intercalary deletions and duplication-deletions were the most frequently induced aberration types. The comparative analysis of the frequency and localization of MMC-induced aberrations in the chromosomes of the two karyotype variants, which differ from each other by the position of the "hot spot" segments, provided new evidence about the influence of the segment transposition on the "hot spot" expressivity. The most remarkable finding obtained in the study is that the size of the segment involved in both intercalary deletions and duplication-deletions proved to be strongly affected by the structural peculiarity of the reconstructed chromosome. The possible reasons underlying this finding are discussed.

NOR activity, heterochromatin differentiation, and the Robertsonian polymorphism in Sus scrofa L.

The karyotype of the European wild pig (Sus scrofa scrofa L.) was analysed by means of silver-staining and the chromomycin A3/distamycin A/DAPI fluorescent banding technique to locate active NORs and to differentiate types of C-bands. The ribosomal RNA genes are localized at the secondary constrictions of chromosomes 8 and 10. All biarmed chromosomes, with the exception of chromosome 15/17 and the Y, had a chromomycin bright centromeric region that was moderately fluorescent with distamycin A/DAPI (DA/DAPI). Conversely, all acrocentric chromosomes and the Robertsonian fusion product (15/17) exhibited DA/DAPI bright centromeric heterochromatin. The results are compared with the chromosomal staining behavior of the domestic pig (Sus scrofa domestica L.) and discussed with respect to presumptive mechanisms of karyotypic evolution.

Partial inversion of the secondary constriction of chromosome 9: it exists.

The pericentric inversion of the heterochromatic region of chromosome 9 [inv(9)(qh)] is a chromosomal variant of particular interest, because of its relatively common occurrence (Madan and Bobrow 1974) and possible deleterious effects (Bou6 et al. 1975; Neri et al. 1981). It has been variously classified into partial and total inversion, according to the relative amount of heterochromatin transferred to the short arm. In a recent issue of Human Genetics, Mattei et al. (1981) raise the question whether the partial inversion of the secondary constriction of chromosome 9 really exists. The authors report cases of apparent partial inversion, based on CBG banding, that were subsequently shown to be normal by the Giemsal l (G-11) technique. They argue that in the majority of cases the false impression of a partial inversion is probably due to an increase in the centromeric heterochromatin without alteration of the secondary constriction, and conclude that true partial inversions must be exceedingly rare. We wish to confirm these results and also to report a case of true partial inversion. A total of 214 apparently healthy subjects were examined over a 10-month period as part of another investigation. Whole blood cultures were set up in RPMI medium, supplemented with 10% fetal calf serum and 10% human serum, and blocked at 70 h with colcemid (0.1 gg/ml). Hypotonic shock was performed with 0.075 M KC1 for 8 min at 37°C and the chromosomes were fixed and washed with methanol : acetic acid (3 : 1). A drop of sample was spread on a wet slide and air-dried. C(CBG) bands were obtained by the method of Sumner (1972), with the following minor modifications. The slides were directly immersed in 3% Ba(OH)2 at 65°C for 20-30 min without prior treatment with hydrochloric acid, followed by renaturation in 2 x SSC for 30min at 65°C, rinsing in tap water, and staining with 10% Giemsa in McIlvaine buffer for 8 min. Specific staining of the secondary constrictions of chromosome 9 was obtained by the G-11 technique, as described by Gagn6 and Laberge (1972). Of a total of 214 cases examined by CBG banding, 11 had a chromosome 9 with apparently partial pericentric inversion of the heterochromatic region. Two additional cases of particular interest were subsequently observed. In one, both chromosomes 9 had an apparent partial inversion, and in the other the inversion looked nearly total. Each of these 13 cases was re-