Inheritance of acrocentric association patterns.

The individual association frequencies of acrocentric chromosomes identified by fluorescent markers were analyzed in 17 individuals from 3 families. The frequency of association appears to be a characteristic property of an individual chromosome, since certain marker chromosomes showed an increase in frequency of association in each family member in which they appeared. Most of the marker chromosomes with increased frequency of association had a longer nucleolar constriction than their homologs.     

Behavior of the nucleolus organizer regions of the chromosomes in polykaryocytes consisting of micronuclei

The nucleolar organizer regions (NORs) of Chinese hamster chromosomes (clone 237, cell line BIId-ii-FAF28) were studied in mononuclear cells and polykaryocytes induced with colcemid. The chromosomes with NORs were marked as 1, 2, 3, 4. The activity of NORs in mononuclear cells was higher in chromosomes 1, 2, 3. The associations of NORs were observed between chromosomes I and 2 (3% of all metaphases). In polykaryocytes the chromosomal pairs 1, 2, 3 showed different NOR activity in different metaphases. The associations of NORs in pairs of chromosome I were found in 51.3% of cases. The associations of NORs in pairs of chromosome 2 were observed in 7.5% of cases. This method may be used for the estimation of association potency of NORs in chromosomes.     

Note on the karyotype and NOR phenotype of leuciscine fish Acanthobrama marmid (Osteichthyes, Cyprinidae)

The karyotype and major ribosomal sites as revealed using silver staining of Anatolian leuciscine cyprinid fish Acanthobrama marmid were studied. The diploid chromosome number was invariably 2n = 50. Karyotype consisted of eight pairs of metacentric, 13 pairs of submetacentric and four pairs of subtelocentric to acrocentric chromosomes. The largest chromosome pair of the complement was subtelo-to acrocentric characteristically, which is a characteristic cytotaxonomic marker for representatives of the cyprinid lineage Leuciscinae. The nucleolar organizer regions (NORs) were detected in the telomeres of two pairs of medium sized submeta-to subtelocentric chromosomes. No heteromorphic sex chromosomes were found. The karyotype pattern of A. marmid is nearly identical to that found in most other representatives of the Eurasian leuciscine cyprinids, while the multiple NOR phenotype appears to be more derived as opposed to a uniform one, ubiquitous in this group.     

Identification of C-banded chromosomes in meiosis and the analysis of nucleolar activity in Avena byzantina C. Koch cv ‘Kanota’

Summary The Giemsa C-banding technique was used to identify individual meiotic and somatic chromosomes in 21 monosomic lines of Avena byzantina C. Koch cv Kanota (genome designation AACCDD). The hexaploid complement is composed of three sets of seven chromosome pairs. The heterochromatin in the putative diploid progenitors is located at the telomeres (genome A), at the centromeric and interstitial regions (genome C), or more evenly spread throughout the set (genome D). Comparisons based on C-banding between A. byzantina and its diploid progenitor species allowed us to allocate individual chromosomes into specific genomes. The C-banding technique may be useful for interspecific chromosome pairing analyses. Nucleolar activity and competition were studied using a silver-staining procedure. Only three chromosome pairs showed nucleolar organizer regions, thus indicating that nucleolar competition occurs naturally in hexaploid oats.     

Effect of increase in ploidy on the activation of nucleolar organizer regions in Chinese hamster ovary (CHO) cells

The effect of increased ploidy on the activation of specific nucleolar organizer regions (NORs) was examined by comparing the distribution and frequency of active NORs in pseudodiploid Chinese hamster ovary (CHO) cells with a quasi-tetraploid hybrid line. Active NORs were identified on both unrearranged chromosomes and isochromosomes of the Z group by silver staining. The increase in cell ploidy in the hybrid did not result in the complete inactivation of specific NORs or the activation of a previously silent NOR. However, for several chromosome pairs identified as carrying NORs, apparent translocations and deletions which produced the karyotype of the pseudodiploid cells deleted or inactivated the NOR of one member of a homologous pair. When two copies of such chromosomes were present in the quasi-tetraploid hybrid line, the activity of their NORs showed apparent coordination. Furthermore, the frequency of activity of individual NORs in two CHO lines and in a quasi-tetraploid hybrid line suggests that active NORs are not inherited directly.     

Dynamics of structural and functional association of nucleolar chromosomes in cells of the hexaploid wheat Triticum aestivum L. at different stages of the cell cycle and during genome polyploidization

Quantitative analysis of interphase association of the nucleolar chromosomes at different stages of the cell cycle and during genome polyploidization was carried out. Cells of various tissues of hexaploid wheat Triticum aestivum L. (Moskovskaya-35) were used, including diploid root meristematic cells, endopolyploid root cells, triploid endosperm cells and antipodal cells with polytene chromosomes. Interphase nucleoli impregnated with silver or stained with autoimmune antibodies to 53 kDa nucleolar protein served as markers of the nucleolar chromosome association. The following data were obtained: (1) silver-staining revealed two pairs of homologous chromosomes 1B and 6B with active nucleolus-organizing regions in the root meristematic cells; (2) maximal number of nucleoli in diploid meristematic cells reaches four, which corresponds to the number of chromosomes with active organizers; (3) analysis of cells at different stages of the cell cycle has shown that the tendency to the nucleoli association is observed as soon as cells pass individual stages of the cycle; (4) after DNA and chromosome reduplication, the nucleolus-organizing regions in sister chromatids function as a common structure-functional complex; (5) in endopolyploid root cells and antipodal cells with polytene chromosomes, the number of nucleoli does not correlate with ploidy level, and an additional nucleolus revealed in some cells is the result of activation of the latent organizer in one of the nucleolar chromosomes; (6) in the triploid endosperm nucleologenesis, the stage of prenucleolar bodies is missing. Our data suggest that "fusion" of nucleoli and reduction of their number due to the "satellite" association of the nucleolar chromosomes are two independent processes regulated by different mechanisms.     

Occurrence of natural triploidy in Rhamdia quelen (Siluriformes, Heptapteridae)

Five specimens of Rhamdia quelen collected from the Lindóia Stream, PR, Brazil, were cytogenetically analyzed. The diploid chromosome number found was 58, including 30 metacentric, 16 submetacentric, 10 subtelocentric, and 2 acrocentric chromosomes. Supernumerary or B chromosomes, frequently observed in this fish group, were not detected. One of the individuals was triploid, with 3n = 87. A silver-stained nucleolar organizer region was found on a pair of submetacentric chromosomes of the diploid specimens, and on three chromosomes of the triploid individual, confirming triploidy. Treatment with fluorochrome chromomycin A(3) revealed fluorescent bands coincident with those of the silver-stained nucleolar organizer region, in both diploid and triploid individuals, showing that this is a GC-rich region. Heterochromatin distribution was visualized by the C-banding technique, mainly in the terminal chromosome regions of the individuals and was also observed in the pericentromeric regions of some chromosomes and at both telomeres.     

Mitotic association patterns of nucleolar organizing chromosomes in the mouse.

Following the report of localization of nucleolar organizer regions to chromosome pairs 15, 18, and 19 of the mouse, a study was undertaken to test these chromosomes for association during mitotic metaphase. Cells from sevel strains of mice were analyzed, and no strong evidence was found for any significant association patterns.     

The Basic Karyotype of Lotus tenuis C-banding and Feulgen Studies

The basic karyotype of L. tenuis is illustrated. The study ofFeulgen stained metaphases has shown that the chromosome complementconsists of four pairs of median chromosomes and two pairs ofsubmedian chromosomes. Two nucleolar constrictions characterizethe first homologous pair. The C-banding pattern includes largepericentric bands in each chromosome pair and a terminal bandin the short arm of chromosome 3 Lotus tenuis, chromosome morphology, C-banding     

Differentiation of interphase nucleolus organizers in embryonic pig kidney cells (PK cell line)

The prometaphase karyotype of cell line PK contains two heteromorphous pairs of nucleolus organizers that belong to chromosomes 8a and 8, and to 10L and 10s. It was proposed that such heteromorphism may promote chromosome differentiating of interphase nucleolus organizers (INOs) with linear configuration. To test this assumption, we used two-dimensional (2D) preparations of methanol fixed PK cells surface stretched without hypotonic treatment. It was shown that in these preparations the large bulk of interphase PK cells contained 3-4 necklace-like linear structures arranged in nucleolar domains. The observed structures were positive in phase contrast and after DAPI-staining. Complimentary rDNA-FISH revealed that these structures were INOs, the largest iNO in individual cells containing prominent terminal rDNA FISH/DAPI signal. In accordance with the data on prometaphase analysis, the latter INOs belong to chromosomes 8a. As reported by Smetana and coworkers (1999), proteins of the nucleolar fibrillar center reacted preferentially with silver in methanol fixed unwashed smears of human peripheral lymphocytes. It was established that the same specific silver reaction is characteristic most probably of 2D preparations of methanol fixed PK cells. Both silver stained and rDNA-FISH linearized INOs had necklace-like or banded structure with different degrees of resolution. Banded INOs consisted of transverse argyrophilic structures: dense bands and loose interbands. High resolved banded INOs revealed a longitudinal splitting (binemic structure) of interband zone. Necklace-like INOs consisted of argyrophilic beads nearly two-fold more narrow than argyrophilic bands, and uninemic or silver-negative interbead zones. Our findings evidence that necklace-like INOs are typical for G1 and S phase cells, whereas banded INOs are characteristic of G2 cells. Among high resolved linear INOs, we found four reproducible patterns of silver staining, which could be combined it two homologous groups. Because each given pattern is unique for individual PK cells, we concluded that the patterns under study were chromosome specific. Using prometaphase analysis data, we determined chromosome affiliation for each of the four tested patterns of INO silver staining. High resolved INOs, belonging to different chromosomes, were further compared with regard to their average length and the mean of argyrophilic bead number per individual INO, in addition to the length and argyrophilic bead number ratios calculated for different INO pairs of individual cells. Surprisingly, we found that both the ratios, detected for most heteromorphous pair of homologous chromosomes 8a and 8, made only 1.26 +/- 0.02. In comparison, the similar length ratio for nucleolus organizers in chromosomes 8a and 8, calculated for individual prometaphase cells, reached 2.92 +/- 0.30.     

Giemsa C-banded karyotypes and taxonomic relationships of some North AmericanAllium species and their relationship to Old World species (Liliaceae)

The somatic karyotypes of six North AmericanAllium species and the EuropeanA. scorzonerifolium have been investigated using a Giemsa C-banding technique. All species have a chromosome number of 2n = 14. InA. scorzonerifolium and the three North American speciesA. dichlamydeum, A. fibrillum andA. unifolium C-bands are restricted to two pairs of nucleolar chromosomes. Each chromosome has a band proximal to the nucleolar constriction and a positively banded satellite. InA. acuminatum, in addition to the bands associated with the nucleolar constrictions, all chromosomes also have pericentromeric bands.A. cernuum exhibits a distinctive banding style: two chromosome pairs with bands adjacent to the nucleolar constrictions and four pairs with telomeric bands on their short arms. In the karyotype ofA. geyeri neither C-bands nor nucleolar chromosomes were found.—A comparison of the banding styles together with other cytological and morphological characters of these species with old world members ofAllium reveals:A. cernuum closely resembles species within subgenusRhizirideum, whereas the other species studies exhibit many similarities with subgenusMolium. Their sectional grouping and their relationships with Old World species are discussed.     

Revision of SAT chromosome number in Triticum monococcum with respect to nucleolar organizers activity

Summary Six varieties of Triticum monococcum were analysed by means of the nucleolar test; i.e., estimation of the maximum number of primary nucleoli per nucleus. All of the varieties exhibited 4 primary nucleoli in telophase and early interphase. Following detailed karyological analysis four SAT chromosomes in all six karyotypes were found in accordance with the maximum nucleolar number. Secondary constrictions and microsatellites were localised on the short arms of chromosome pairs 3 and 5. A new order of the chromosomes in the idiogram of Tr. monococcum is proposed.     

The origin of mitotic sex-chromosome association in the brush-tailed possum, Trichosurus vulpecula (marsupalia:phalangeridae)

Nonrandom associations between the sex chromosomes of the brush-tailed possum, Trichosurus vulpecula, were found to be due to association of nucleolar organizer regions (NOR's) on the X and Y chromosomes. NOR association was also observed between an autosome and the X chromosome. These findings, based on silver staining, are in contrast to the report of MURRAY (1977), who observed sex-chromosome association in this animal and indicated that these nonrandom associations may reflect an association between heterochromatic regions during interphase. We observed only two pairs of NOR's per cell in this animal, one autosomal and one on the sex chromosomes, rather than the several such regions observed by MURRAY, who used an N-banding technique. We discuss the problem of nonhomologous chromosome association in mammalian cells as influenced by heterochromatin and NOR's and find little support for nonhomologous chromosome associations at mitotic metaphase due to heterochromatin association.     

兴义维蚋多线染色体研究（英文）

首次在国内对兴义维蚋Simulium (Wilhelmia) xingyiense的多线染色体进行研究, 并提供其多线染色体标准图。选取兴义维蚋的成熟幼虫, 用改良苯酚品红染色法进行唾腺多线染色体制备, 并进行测量、 描述及分析。结果表明： 兴义维蚋多线染色体数目为3对（2n=6）。Ⅰ号染色体具中央着丝粒, Ⅱ和Ⅲ号染色体均为亚中央着丝粒染色体。核仁组织者区位于Ⅰ号染色体短臂近着丝粒端。巴尔比尼氏环和双泡位于Ⅱ号染色体短臂近中央位置。3对染色体的着丝粒区可形成明显的染色中心。兴义维蚋多线染色体具有多态性的倒位, 倒位频率为0.64。兴义维蚋多线染色体的着丝粒、 核仁组织区、 巴氏环、 双泡等主要特征性结构的位置及形态恒定一致,可作为该种的重要鉴别特征。其多态性的倒位可为该蚋种在细胞水平上进行蚋类分类鉴别和系统发育等研究提供基础资料。     

Novel repeated DNA sequences in safflower (Carthamus tinctorius L.) (Asteraceae): cloning, sequencing, and physical mapping by fluorescence in situ hybridization

Two novel repetitive DNA sequences, pCtKpnI-1 and pCtKpnI-2, were isolated from Carthamus tinctorius (2n = 2x = 24) and cloned. Both represent tandemly repeated sequences. The pCtKpnI-1 and pCtKpnI-2 clones constitute repeat units of 343-345 bp and 367 bp, respectively, with 63% sequence heterogeneity between the two. Fluorescence in situ hybridization (FISH) was employed on metaphase chromosomes of C. tinctorius using, simultaneously, pCtKpnI-1 and pCtKpnI-2 repeated sequences. The pCtKpnI-1 sequence was found to be exclusively localized at subtelomeric regions on most of the chromosomes. On the other hand, sequence of the pCtKpnI-2 clone was distributed on two nucleolar and one nonnucleolar chromosome pairs. The satellite, and the intervening chromosome segment between the primary and secondary constrictions, in the two nucleolar chromosome pairs were wholly constituted by pCtKpnI-2 repeated sequence. The pCtKpnI-2 repeated sequence, showing partial homology to intergenic spacer (IGS) of 18S-25S ribosomal RNA genes of an Asteraceae taxon (Centaurea stoebe), and the 18S-25S rRNA gene clusters were located at independent, but juxtaposed sites in the nucleolar chromosomes. Variability in the number, size, and location of the two repeated sequences provided identification of most of the chromosomes in the otherwise not too distinctive homologues within the complement. This article reports the start of a molecular cytogenetics program targeting the genome of safflower, a major world oil crop about whose genetics very little is known.     

Nucleolar organizing chromosomes ofRicinus

Summary Pachytene chromosome morphology was compared in nine races ofRicinus communis L. (2n = 20), using pollen mother cells (PMCs) and light microscopy. Of the ten bivalents, only the two possessing nucleolar organizing regions (NORs), chromosomes 2 and 7, exhibit structural variations among the races. The NORs are located in the short arms of these two chromosomes. Most of the observed structural variations affect these short arms, which are similar morphologically and consist largely of heterochromatic segments. The PMCs contain a single nucleolus and this is associated with the NOR of each of the two chromosomes at a particular frequency in each race. In eight races, a nucleolar constriction (NC) is present in either chromosome 2 or chromosome 7. In these races, the nucleolus is associated with the chromosome possessing an NC at a frequency of 100% and with the chromosome lacking an NC at a frequency ranging between 5.6 and 100%, depending upon the race. No microscopically visible NC is present in the ninth race. In this race, the nucleolus is associated with both chromosomes 2 and 7 at a frequency of 100%. The association of the nucleolus with a chromosome possessing an NC is at the NC and with a chromosome lacking an NC is at the terminal heterochromatic segment of the short arm. Several interpretations are offered to account for the variations in frequency of association between the nucleolus and each of the nucleolar organizing chromosomes. It is suggested that the two non-linked NORs have evolved through some intragenomic changes rather than polyploidy, that this species is highly intolerant to structural variations other than those occurring in or near the NORs, and that structural variations in the nucleolar organizing chromosomes are not associated with racial variations in plant phenotype.Paper of the Journal Series, New Jersey Agricultural Experiment Station     

The characterization of somatic chromosomes of Gymnothorax unicolor (Delaroche, 1809) by C-banding and NOR staining (Osteichthyes,Anguilliformes)

The diploid chromosome number of Gymnothorax unicolor (Delaroche, 1809) is 2n=42, the karyotype comprising six pairs of meta-submetacentric and fifteen pairs of acrocentric chromosomes. C-positive chromatin is present in the centromeres of all chromosomes as well as in the paracentromeric regions of some chromosomes. A nucleolar organizer region was identified on the long arm of chromosome 9, near the centromere. This region is also positive to C-banding.Cytotaxonomical relationships are evidenced between the described karyotype and that of the related species Muraena helena.     

Cytogenetic analysis of some Brazilian marsupials (Didelphidae: Marsupialia)

Three species of marsupials from the Amazon region (Marmosa cinerea, Caluromys lanatus, and Didelphis marsupialis) and two from the region of S?o Paulo (Didelphis marsupialis and Didelphis albiventris) were studied. The G-banding pattern of the species with 2n = 14 (M. cinerea and C. lanatus) was very similar, as well as the pattern of G-bands in the species with 22 chromosomes (Didelphis). All of the autosomes of M. cinerea and D. albiventris have centromeric C-bands and the Y chromosome is totally C-band positive. The long arm of the M. cinerea X chromosome is completely C-band positive except for a negative band close to the centromeric region. In D. albiventris the long arm of the X chromosome is C-band positive except for a negative band close to the telomeric region. In M. cinerea the silver-stained nucleolar organizer regions (Ag-NORs) are found in the acrocentric chromosomes, being located in the telomeric region of one pair and in the centromeric region of the other pair. Caluromys lanatus has centromeric Ag-NORs in one acrocentric and in one submetacentric chromosome pairs. Didelphis marsupialis has three chromosome pairs with telomeric Ag-NORs. In D. albiventris the Ag-NORs are terminal and located in both arms of one pair and in the long arm of two pairs of chromosomes.     

A cytogenetic analysis in Psophus stridulus (L.) (Orthoptera: Acrididae): B-chromosomes and abnormal spermatid nuclei

The male chromosome complement of Psophus stridulus (L.) (Orthoptera: Acrididae) has been analyzed by using orcein staining, C-banding and silver impregnation. During spermatogenesis only one pair of autosomes (M₉) shows an active nucleolar organizer region located in a C-banded constriction. There are other chromosome pairs with constrictions but these do not show nucleolar activity. The relationship between these constrictions and the C-banding pattern exhibited by this species is analyzed.In a sample of 83 males from five populations, two different supernumerary chromosomes were observed. Four males had a metacentric B-chromosome (B^m) similar in size to the sex chromosome and mitotically stable. Its meiotic behaviour indicates that it is an isochromosome. An additional small B-chromosome (B⁸) was also found in a single follicle of one individual carrying the B^m.A high rate of abnormal spermatids (macrospermatids) was scored in the individuals carrying B's. This proportion is notably higher in the follicle containing both the B^m and the B⁸.     

Relative position of trypsin banded homologous chromosomes in human (female) metaphase figures.

"Generalized distances" between centromeres were statistically analyzed (chi2 test) on 50 normal female trypsin-banded metaphase figures. This study revealed that the homologous chromosomes of the pairs 13, 17, 14, and 21 lie closer together than would be expected by a reference distribution, and this in a statistically significant way. The same relative position was demonstrated for the chromosome groups 13-14, 13-21, 14-21, 15-22, and 14-22. Evidences were collected that also showed that homologous chromosomes of the pairs 1, 19, and 20 and the chromosome groups 15-21, 13-15, and 18-20 tend to lie closer together. Giving a functional interpretation to the phenomenon of non-random distribution of chromosomes in metaphase figures, it may be suggested that the chromosomes 13, 14, and 21 are involved in the organization of the human nucleolar organizers, more frequently than the other D- and G-group chromosomes.