Metacentric Chromosomes Research Articles

Karyotype analysis and visualization of 45S rRNA genes using fluorescence in situ hybridization in aroids (Araceae).

Karyotype analysis and FISH mapping using 45S rDNA sequences on 6 economically important plant species Anthurium andraeanum Linden ex André, 1877, Monstera deliciosa Liebmann, 1849, Philodendron scandens Koch & Sello, 1853, Spathiphyllum wallisii Regel, 1877, Syngonium auritum (Linnaeus, 1759) Schott, 1829 and Zantedeschia elliottiana (Knight, 1890) Engler, 1915 within the monocotyledonous family Araceae (aroids) were performed. Chromosome numbers varied between 2n=2x=24 and 2n=2x=60 and the chromosome length varied between 15.77 µm and 1.87 µm. No correlation between chromosome numbers and genome sizes was observed for the studied genera. The chromosome formulas contained only metacentric and submetacentric chromosomes, except for Philodendron scandens in which also telocentric and subtelocentric chromosomes were observed. The highest degree of compaction was calculated for Spathiphyllum wallisii (66.49Mbp/µm). B-chromosome-like structures were observed in Anthurium andraeanum. Their measured size was 1.87 times smaller than the length of the shortest chromosome. After FISH experiments, two 45S rDNA sites were observed in 5 genera. Only in Zantedeschia elliottiana, 4 sites were seen. Our results showed clear cytogenetic differences among genera within Araceae, and are the first molecular cytogenetics report for these genera. These chromosome data and molecular cytogenetic information are useful in aroid breeding programmes, systematics and evolutionary studies.

<b>Karyotypic characterization of <i>Capsicum</i> sp. accessions

This study aimed to determine the chromosome number and the karyotype of Capsicum annuum, Capsicum chinense, Capsicum frutencens and Capsicum baccatum accessions in the active Capsicum sp. genebank at the Federal University of Piaui (BGC-UFPI). These species have great economic importance throughout the world, and their cytogenetic characterization can inform taxonomy and lead to improvement in the genus. Karyotypes were obtained from the rootlet meristems of the studied accessions using the squash method and Giemsa staining. The chromosome number 2n=2x=24 was verified for each of the four species. Chromosomal polymorphisms were observed for the C. frutencens accession BGC 37, which presented 12 pairs of metacentric chromosomes instead of 11 pairs of metacentric chromosomes and 1 submetacentric chromosome pair present in other accessions. In the accessions BGC 01 and BGC 37, secondary constrictions were observed in the 1 and 12 as well as in the 6 and 11 homologs, respectively. The karyotypes of the studied species were asymmetrical among themselves. The results obtained in this study confirm the high genetic diversity previously described in the literature for this genus.

Fagopyrum luojishanense, a New Species of Polygonaceae from Sichuan, China

Fagopyrum luojishanense J. R. Shao, a new species of Fagopyrum Mill. (Polygonaceae), is described and illustrated from Liangshan in Sichuan Province, China. This species is distinguished by its leaf blades that are ovate, narrowly ovate or triangular, winged seeds, and inflorescences that are either axillary or terminal, and we further distinguish the new species based on karyotype analysis. Fruit surface ornamentation of F. luojishanense is densely and irregularly warty, while fruit ornamentation is sparser in F. gracilipes (Hemsl.) Dammer ex Diels. Fagopyrum luojishanense is a diploid taxon, with 2n = 2x = 16 and a karyotype of 16 metacentric chromosomes, while F. gracilipes is tetraploid, 4n = 4x = 32, with a karyotype of 30 metacentric and two submetacentric chromosomes.

Integration of genetic and physical maps of the Primula vulgaris S locus and localization by chromosome in situ hybridization.

Summary Heteromorphic flower development in Primula is controlled by the S locus. The S locus genes, which control anther position, pistil length and pollen size in pin and thrum flowers, have not yet been characterized. We have integrated S‐linked genes, marker sequences and mutant phenotypes to create a map of the P. vulgaris S locus region that will facilitate the identification of key S locus genes. We have generated, sequenced and annotated BAC sequences spanning the S locus, and identified its chromosomal location.We have employed a combination of classical genetics and three‐point crosses with molecular genetic analysis of recombinants to generate the map. We have characterized this region by Illumina sequencing and bioinformatic analysis, together with chromosome in situ hybridization.We present an integrated genetic and physical map across the P. vulgaris S locus flanked by phenotypic and DNA sequence markers. BAC contigs encompass a 1.5‐Mb genomic region with 1 Mb of sequence containing 82 S‐linked genes anchored to overlapping BACs. The S locus is located close to the centromere of the largest metacentric chromosome pair.These data will facilitate the identification of the genes that orchestrate heterostyly in Primula and enable evolutionary analyses of the S locus.

Karyological, morphological, and phylogenetic diversification in Leucocoryne Lindl (Allioideae, Amaryllidaceae)

The genus Leucocoryne (Amaryllidaceae) comprises approximately 15 species and is the only genus of the tribe Ipheieae endemic to the western region of Chile in sclerophyll and arid winter-rainfall biomes in the Andes. To better understand the karyotype diversification of this genus, nine species of Leucocoryne were analyzed in terms of their chromosome number and morphology, CMA and DAPI heterochromatic bands, distribution of rDNA sites, and their molecular phylogenetic relationships. Based on phylogenetic analyses Leucocoryne was divided in four clades: I (L. alliacea and L. conferta); II (L. dimorphopetala and L. narcisoides); III (L. coquimbensis, L. macropetala, L. appendiculata, L. talinensis, L. angustipetala, L. purpurea, and L. violacescens); and IV (L. vittata, L. ixioides, L. foetida, and L. pauciflora). The species were diploids with 2n = 10 (6M + 4A) or tetraploids with 2n = 18 (14M + 4A)/2n = 19 (13M + 6A). 45S rDNA sites were co-localized with CMA+/DAPI− bands on the short arms of acrocentric chromosomes in all species. 5S rDNA sites were observed on one, two, or four pairs of metacentric chromosomes per species. Estimations of the ancestral karyotype suggest that 2n = 10 (6M + 2A) with one 5S rDNA site per monoploid complement was the plesiomorphic condition of the genus Leucocoryne. Increases in number of 5S rDNA sites in the same species associated with biome shifts from sclerophyll to arid winter-rainfall region occurred independently in clade II and clade III. The two species of clade II retained the six fertile stamens (plesiomorphic condition) in contrast to the other Leucocoryne species that reduced to only three functional stamens. Based on these findings, we discuss the role of environmental change on the diversification of this group.

Comparative cytogenetics of North Island tree wētā in sympatry

In North Island New Zealand three species of tree wētā (Hemideina) have narrow regions of overlap. Using detailed measurements of chromosomes we compared the karyotypes of Hemideina thoracica with those of Hemideina crassidens and Hemideina trewicki. Although H. thoracica and H. trewicki have the same diploid number (2n = 17 [XO], 18 [XX]), distinct from H. crassidens (2n = 15 [XO] 16 [XX]); the karyotypes of H. trewicki and H. crassidens are more similar to each other than either is to H. thoracica. Elements within each karyotype were identified that are species specific and will aid identification of putative hybrids. Quantitative cytogenetics was used to identify the sex chromosome for H. crassidens and H. trewicki, which in contrast to previous inferences, is most likely the fifth-longest metacentric chromosome in H. crassidens, and the third-longest metacentric chromosome in H. trewicki.

Karyomorphology of three species ofAristolochia– rare and endemic medicinal plants of Assam, India

Karyomorphological analyses were conducted of three species of Aristolochia from Assam, India: Aristolochia indica Linn., Aristolochia saccata Wall., and Aristolochia cathcartii Hook. f. The study included determination of somatic chromosome number, total chromosome length, volume, arm ratio and centromeric position. Chromosome classification was done on the basis of the position of the centromere. Their karyotypes were as follows: 2n = 12 for Aristolochia indica Linn. and Aristolochia saccata Wall., and 2n = 20 for Aristolochia cathcartii Hook. f. A. indica consists of six median chromosomes and six metacentric chromosomes. The chromosome length varied from 1.36 μm to 3.06 μm while their volumes ranged from 0.004 μm3 to 0.176 μm3. The relative length of the chromosomes varied from 5.71 μm to 12.85 μm. A. saccata possesses six median, two metacentric and two submetacentric chromosomes. One pair of metacentric chromosome possesses secondary constriction at subterminal region. The chromosome length varied f...

Establishment and characterization of fin cell lines from diploid, triploid, and tetraploid oriental weatherfish (Misgurnus anguillicaudatus).

Continuous fin cell lines from diploid, triploid, and tetraploid oriental weatherfish, Misgurnus anguillicaudatus, were established and characterized. The cell lines, designated DIMF, TRMF, and TEMF, respectively, were subcultured more than 80 times since initiation in October 2012 and were preserved at the China Center for Type Culture Collection as sample numbers C2013109, C2013110, C2013111, respectively. The cell lines consist predominantly of fibroblast-like cells. At the 50th passage, the population doubling times were 48.43h (DIMF), 36.01h (TRMF), and 41.45h (TEMF). Cell survival rate of these three kinds of cells was 80.88±1.38, 84.48±1.13, and 81.57±1.28%, respectively, when recovered after storage in liquid nitrogen for 60days at the 40th passage. The chromosome numbers measured from 100 metaphase plates at the 50th passage were 2n=50 (68%), 3n=75 (59%), and 4n=100 (54%) for DIMF, TRMF, and TEMF cells, respectively. At the 60th passage, the chromosome numbers for DIMF and TRMF cells were still 50 (52%) and 75 (70%), but the chromosome number for TEMF cells ranged from 88 to 100; a chromosome number of 96 accounted for 26% of the cells, and the karyotype analysis showed 4n=96, 16m+8sm+72t, NF=120; thus, compared with cells at the 50th passage, a group of metacentric chromosomes was missing. Microsatellite marker analysis was conducted using DIMF, TRMF, and TEMF cells and muscle tissue of oriental weatherfish, which confirmed that the three cell lines established in this study were from oriental weatherfish. The cell lines were exposed to two fish viruses to determine their susceptibility to infection; they were susceptible to spring viremia of carp virus but not to piscine nodavirus. Establishment of fin cell lines from different ploidy oriental weatherfish increases the existing number of fish cell lines available for research, and it provides a model for investigating the mechanisms of growth and genetics in polyploid fish.

Specific features in linear and spatial organizations of pericentromeric heterochromatin regions in polytene chromosomes of the closely related species Drosophila virilis and D. kanekoi (Diptera: Drosophilidae).

Heterochromatin plays an important role in the spatial arrangement and evolution of the eukaryotic genetic apparatus. The closely related species Drosophila virilis (phyla virilis) and D. kanekoi (phyla montana) differ in the amount of heterochromatin along the chromosomes as well as by the presence of the metacentric chromosome 2, which emerged as a result of a pericentric inversion during speciation, in the D. kanekoi karyotype. The purpose of this study was to establish if chromosome rearrangements have any influence on the linear redistribution of centromeric heterochromatin in polytene chromosomes and the spatial organization of chromosomes in the nuclei of nurse cell. We have microdissected the chromocenter of D. virilis salivary gland polytene chromosomes; obtained a DNA library of this region (DvirIII); and hybridized (FISH) DvirIII to the salivary gland and nurse cell polytene chromosomes of D. virilis and D. kanekoi. We demonstrated that DvirIII localizes to the pericentromeric heterochromatin regions of all chromosomes and peritelomeric region of chromosome 5 in both species. Unlike D. virilis, the DvirIII signal in D. kanekoi chromosomes is detectable in the telomeric region of chromosome 2. We have also conducted a 3D FISH of DvirIII probe to the D. virilis and D. kanekoi nurse cell chromosomes. In particular, the DvirIII signal in D. virilis was observed in the local chromocenter at one pole of the nucleus, while the signal belonging to the telomeric region of chromosome 5 was detectable at the other pole. In contrast, in D. kanekoi there exist two separate DvirIII-positive regions. One of these regions belongs to the pericentromeric region of chromosome 2 and the other, to pericentromeric regions of the remaining chromosomes. These results suggest that chromosome rearrangements play an important role in the redistribution of heterochromatin DNA sequences in the genome, representing a speciation mechanism, which, in general, could also affect the chromosome orientation in the 3D nuclear space.

Cytogenetic analysis and chromosomal characteristics of the polymorphic 18S rDNA of Haliotis discus hannai from Fujian, China.

We report on novel chromosomal characteristics of Haliotis discus hannai from a breeding population at Fujian, China. The karyotypes of H. discus hannai we obtained from an abalone farm include a common type 2n = 36 = 10M + 8SM (82%) and two rare types 2n = 36 = 11M + 7SM (14%) and 2n = 36 = 10M + 7SM + 1ST (4%). The results of silver staining showed that the NORs of H. discus hannai were usually located terminally on the long arms of chromosome pairs 14 and 17, NORs were also sometimes located terminally on the short arms of other chromosomes, either metacentric or submetacentric pairs. The number of Ag-nucleoli ranged from 2 to 8, and the mean number was 3.61 ± 0.93. Among the scored interphase cells, 41% had 3 detectable nucleoli and 37% had 4 nucleoli. The 18S rDNA FISH result is the first report of the location of 18S rDNA genes in H. discus hannai. The 18S rDNA locations were highly polymorphic in this species. Copies of the gene were observed in the terminal of long or/and short arms of submetacentric or/and metacentric chromosomes. Using FISH with probe for vertebrate-like telomeric sequences (CCCTAA)3 displayed positive green FITC signals at telomere regions of all analyzed chromosome types. We found about 7% of chromosomes had breaks in prophase. A special form of nucleolus not previously described from H. discus hannai was observed in some interphase cells. It consists of many small silver-stained nucleoli gathered together to form a larger nucleolus and may correspond to prenucleolar bodies.

Co-occurrence of mosaic supernumerary isochromosome 18p and intermittent 2q13 deletions in a child with multiple congenital anomalies

The present study deals with karyotpye–phenotype correlations in a six month old child with multiple congenital abnormalities. Cytogenetic analysis revealed mosaicism of a small metacentric supernumerary marker chromosome with a karyotype mos 47,XY+mar[34]/46,XY[31]. Cytogenetic microarray result showed three copies of chromosome 18p (15,400kb in size). Moreover, 255kbp intermittent deletion of chromosome 2q13 involving RGPD5, RGPD6, LIMS3, and LIMS3-LOC440895 was also observed. Correlating microarray data with the mosaic karyotype, the marker chromosome was identified as mosaic isochromosome 18p and was found to be 32,600kbp in size. Baby resembled clinical characteristics of trisomy chromosome 18p, isochromosome 18p and trisomy chromosome 18. The present study suggested that deletion of evolutionarily conserved developmental genes (RGPD5, RGPD and LIMS3) in the 2q13 region might have contributed to more severity in phenotype as compared to so far such reported cases of 18p trisomy's, as these are involved in nuclear-cytoplasm trafficking, signaling for tissue patterning and differentiation.

Impact of the number of Robertsonian chromosomes on germ cell death in wild male house mice.

Previous studies in the house mouse have shown that the presence of Robertsonian (Rb) metacentric chromosomes in heterozygous condition affects the process of spermatogenesis. This detrimental effect mainly depends on the number of metacentrics involved and the complexity of the resulting meiotic figures. In this study, we aimed at elucidating the relationship between the chromosomal composition and spermatogenesis impairment in mice present in an area of chromosomal polymorphism (the so-called Barcelona system BRbS) in which Rb mice are surrounded by all acrocentric animals, no established metacentric races are present and the level of structural heterozygosity is relatively low. Using the terminal deoxinucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assay, we report higher frequency of apoptotic spermatogenetic cells in mice carrying six pairs of metacentrics at the homozygous state than in those carrying two or three fusions at the heterozygous state. Specifically, we detected a higher frequency of TUNEL-positive (T+) tubules and of T+ cells per tubule cross section and also a lower spermatid/spermatocyte ratio. These results indicate that the number of metacentrics at the homozygous state is more influential in determining apoptotic germ cell death than that of moderate chromosome heterozygosity. The percentage of germ cell death lower than 50% found in our samples and the geographic distribution of the set of metacentrics within the BRbS indicate that although the spermatogenic alterations detected in this area could act as a partial barrier to gene flow, they are not sufficient to prevent Rb chromosomes from spreading in nature.

Genotypic variations of ten Indian cultivars ofColocasia esculentavar.antiquoromSchott. evident by chromosomal and RAPD markers

Detailed karyotype, genome size and RAPD marker analysis were employed to assess genetic diversity in Taro (Colocasia esculenta var antiquorom Schott.). Karyotype analysis revealed genotype specific chromosomal characteristics and structural alterations in chromosome with variations of ploidy from 2n = 2x = 28 (cv. Mothan, cv. Muktakeshi, cv. Sree Kiran, cv. Sree Pallavi, cv. Sunajhili) to 3n = 3x = 42 (cv. Banky, cv. DP-25, cv. Duradin, cv. H-3, cv. Telia) in the genome. Highly significant variations in the genomic length, volume and total form (TF) % were noted at variety level. Total genomic chromosome length varied from 46.96μm in cv. Sree Kiran to 100.49μm in cv. Duradin. Total genomic chromosome volume varied from 18.22μm3 in cv. Sunajhili to 38.22μm3 in cv. Duradin. Total form percentage was varied from 24.94% in cv. Sree Kiran to 39.04% in cv. H-3 confirming near metacentric to metacentric chromosomes in the karyotype. Significant variations in the 4C DNA content noted among the cultivars that ranged from 7.24 pg in cv. Sree Kiran to 18.24 pg in cv. Duradin; accordingly, genome size varied from ~7095 to 17875 Mbp. High genome size in all the triplod varieties with 3x = 42 chromosomes could be due to the presence of extra set of chromosomes in the genome or high amount of repetitive DNA. The variation in the genome size at the variety level might be attributed to loss or addition of highly repetitive sequences in the genome. Amplification of genomic DNA in 10 genotypes using Operon primers yielded 230 amplified DNA fragments, ranging in size from 200 to 2500bp out of which 79 bands were polymorphic. A total of 8 unique RAPD bands were observed among 10 taro genotypes that revealed primer wise polymorphism ranged from 16.66 to 47.36% with an average polymorphic percentage of 34.34%. Whereas, among the cultivars the polymorphic percentage varied from 3.70% between cv. DR-25 & cv. Duradin and cv. Telia & cv. H-3 to 41.94% between cv. Mothan & cv. Muktakeshi. Genetic similarity based on Jaccard’s coefficient varied from 0.54 to 0.96, indicating wide genetic variability among the varieties based on RAPD markers. Similarity measures and cluster analysis generally reflected the expected trends in relationships of diploid and triplod taro varieties. Dendrogram obtained from the genetic distances among the varieties could be useful for breeders to choose the diverse parents for breeding programme aimed at varietal improvement.

Cytogenetic Characterization of the Genome of Interspecies Hybrids (Alopex-Vulpes)

Abstract Creation of interspecific hybrids is widely common among plants and animals in order to improve economically important traits for humans. The studied material consisted of chromosomal preparations in the metaphase stage obtained from interspecies hybrids of arctic foxes (Alopex lagopus) and red foxes (Vulpes vulpes). The aim of the study was to analyze the karyotype of the interspecific hybrids taking into account the number of chromosomes of sets A and B. With the use of techniques of classical cytogenetics (C bands, AgNOR bands) and molecular cytogenetics (FISH, PRINS) we carried out a genome analysis of Alopex-Vulpes hybrids. The results of this study showed that chromosomal markers of the interspecies hybrids are inherited from the parent species and are a result of combination of their two genomes. However, intraindividual differences are also observed which may result from aberrations of chromosome segregation during embryonic development. This may lead to the formation of different cell lines with different karyotypes (mosaicism). Moreover, chromosomes of the interspecies hybrids showed telomeric signals at the ends, in the centromers, as well as short chromosome arm rich in heterochromatin. The use of PRINS method led to identification of nucleolus organizer regions on 12 chromosomes of the interspecies hybrids. The hybridization signals obtained were characterized by different size and intensity. In addition, single copies of rDNA in the centromeric regions of several metacentric chromosomes were identified.

Morpho-criteria and karyotype studies in three mulberry varieties

Morpho-criteria, karyotype analysis, chromosome number and ploidy levels were studied for three mulberry varieties. Mysore local and RFS-175 is diploid with 2n=28 and BC2-59 is triploid with 2n=42 somatic chromosomes numbers respectively. Somatic chromosome length ranges from 1.29 m to 3.29 m where as arm ratio ranges from 0.59 to 1.00 m. Karyotypes of these taxa are symmetric. Only metacentric and submetacentric chromosomes are found in the somatic complement. Stomatal frequency is lesser in triploid variety when compared to diploid varieties.

Karyotypic studies of the genus Cuscuta L. (Convolvulaceae) in Saudi Arabia and their taxonomic significance

Chromosome numbers and karyotype criteria of ninespecies of the genus Cuscuta L. (Convolvulaceae) in SaudiArabia were investigated. Chromosomes counts wererecorded in four species for the first time in this study.Chromosome number, based on x=7 has been found in themajority of the studied Cuscuta species. A diploid number(2n=14) was recorded in five species, while tetraploidnumber (2n=28) was recorded in two species whereas 2n=56was recorded in C. campestris. However, 2n=30 based onx=6 was recorded in C. monogyna. The chromosomes in thestudied species of Cuscuta are generally small with a meansize ranging between 0.74 and 1.10 μm. Short chromosomeswere particularly found in C. planiflora (MCL=0.74 μm) andC. chinesis (MCL=0.79), whereas longer chromosomes werescored in C. campestris (MCL=1.10). The karyotype in thestudied species is mostly comprised of metacentric tosubmetacentric chromosomes as indicated by their mean armratio that ranges between 1.31 in C. monogyna and 1.83 in C.planiflora. The degree of karyotype asymmetry is indicatedby high values of TF% ranges between 28.33 in C. planifloraand 40.54 in C. campestris. The A1 value ranged between0.22 in C. planiflora and 0.43 in C. palaestina. Among theexamined species, karyotype features were used to assess the classification of the Cuscuta species in Saudi Arabia in the light of the current systems of classification.

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

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

Karyotypes of some species of the genusLessingianthus(Vernonieae, Asteraceae) and taxonomic implications

We determined the karyotypes of nine species of Lessingianthus, eight of which are here analyzed for the first time. The results include the first chromosome count for L. plantaginoides, which is tetraploid with 2n = 64. All species showed a high proportion of metacentric chromosomes combined with a lower proportion of submetacentric pairs. Only L. coriaceus had a subtelocentric chromosome pair. B chromosomes were observed in L. coriaceus and L. varroniifolius, which were subtelocentric. Differences among the karyotypes of the studied species were small, suggesting that karyotype diversity in the genus evolved by small changes in the structure of chromosomes. Karyotype features appear useful to distinguish Lessingianthus from the closely related genera Chrysolaena and Lepidaploa.

Aneuploidy in spermatids of Robertsonian (Rb) chromosome heterozygous mice.

Rb translocations are chromosomal rearrangements frequently found in natural populations of the house mouse Mus musculus domesticus. The standard diploid karyotype of the house mouse consisting of 40 telocentric chromosomes may be reduced by the emergence of metacentric Rb chromosomes. Multiple simple Rb heterozygotes form trivalents exhibiting higher anaphase nondisjunction frequency and consequently higher number of unbalanced gametes than in normal males. This work will attempt to establish whether frequencies of aneuploidy observed in heterozygote spermatids of the house mouse M. musculus domesticus show differences in chromosomes derived from different trivalents. Towards this goal, the number and distribution frequency of aneuploidy was assessed via FISH staining of specific chromosomes of spermatids derived from 2n = 32 individuals. Our results showed that for a given set of target chromosomes, 90 % of the gametes were balanced, resulting from alternate segregation, and that there were no differences (approx. 10 %) in aneuploidy frequencies in chromosomes derived from different trivalents. These observations suggest that segregation effectiveness does not depend on the type of chromosomes involved in trivalents. As a consequence of the trivalent’s configuration, joint segregation of the telocentric chromosomes occurs thus favoring their appearance together in early spermatids. Our data suggest that Rb chromosomes and their telocentric homologs are subject to architectural constraints placing them close to each other. This proximity may ultimately facilitate fusion between them, hence contributing to a prevalence of Rb metacentric chromosomes.

Karyotype analysis on 11 species of the genus Clematis

In order to explore the karyotype and evolutionary trend of Clematis and provide taxonomically useful data, the chromosome number, the number and position of satellites, the karyotype formulae, the karyotype, arm ratio, relative length centromeric index, and the index of the karyotype asymmetry of 11 species of the genus Clematis were studied. All the analyzed species showed the same stable chromosome number (2n = 2x = 16) and basic chromosome number 8. Clematis karyotypes are composed by metacentric, submetacentric, and terminal centromeric chromosomes. Clematis lanuginosa, C. otophora, C. lasiandra, C. shenlungchiaensis, C. florida var. plena, C. fusca var. violacea, C. crispa, and C. viticella belong to Type 2A, a very symmetric and plesiomorphic type. Clematis henryi, C. integrifolia, and C. japonaca belong to Type 2B, which is apomorphic relative to the other group. The 11 species of Clematis are different in karyotype parameters providing data for the taxonomy of the genus.