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1.
Intrachromosomal asymmetry, one of the two aspects of karyotype asymmetry, increases because of shifts of the centromere position from the median/submedian to terminal or subterminal. Conventional measures of asymmetry use comparisons with the most symmetrical karyotype and thus are an absolute measure of variation in the centromeric index. Conversely, the CVCI index, the coefficient of variation for the centromeric index, only evaluates the relative variation in the centromeric index. We performed a detailed analysis of the capability of the CVCI index and conventional measures of karyotype asymmetry to accurately characterize differences in intrachromosomal asymmetry. Our results show that the CVCI index is unable to accurately evaluate intrachromosomal asymmetry. In fact, the CVCI index evaluates a different measure than other conventional measures of karyotype asymmetry. Therefore, to avoid confusion, we propose that the variation evaluated by the CVCI index should be named heterogeneity of the centromeric index. 相似文献
2.
Kuniaki Watanabe Tetsukazu Yahara Tetsuo Denda Keiko Kosuge 《Journal of plant research》1999,112(2):145-161
Brachyscome and 8 taxa of its allied genera, Australian Astereae. Statistical tests regarding correlations between changes in chromosome
number, total chromosome length, mean chromosome length, karyotypic asymmetry and chromosome length heterogeneity and changes
in habit were performed based on the matK molecular phylogenetic tree. The reductions in chromosome number and total chromosome length, and the increases in mean chromosome
length, chromosome length heterogeneity and karyotypic asymmetry were found to be correlated with the change in habit from
perennial to annual. A reduction in total chromosome length is favored to shorten the mitotic cell cycle and to produce smaller
cells conducive to more rapid development of smaller annuals under the time-limited environment. Stepwise dysploidal reductions
in chromosome number were achieved through the translocation of large chromosome segments onto other chromosomes, followed
by the loss of a centromere, resulting in one fewer linkage group and one fewer haploid chromosome. The correlations between
the dysploidal reduction in chromosome number and the increases in mean chromosome length, length heterogeneity and asymmetry
in karyotype can be attributed to this mode of chromosomal change. These changes occurred independently in several different
lineages in Brachyscome.
Received 27 May 1998/ Accepted in revised form 18 January 1999 相似文献
3.
B. Paszko 《Plant Systematics and Evolution》2006,258(1-2):39-48
In literature seven different methods of evaluating karyotype asymmetry – the TF%, the As K%, Stebbins' classification, the
Rec and the Syi, the A1 and the A2, the DI, and the A – are used for the elucidation of phylogenetic relationships and taxonomic treatments within a particular
group or taxon. The investigation of these seven methods reveals that the intervals used by Stebbins to separate the different
types of karyotype asymmetry are very broad and only one quantitative parameter, the A2 index, correctly describes the variation in chromosome length in a complement. A new asymmetry index (AI) is proposed to
measure karyotype asymmetry and a new parameter, the CVCI, is offered, that precisely assesses the relative variation in centromere position in a complement. The AI index, the CVCI and the CVCL (=A2 × 100) have the potential to display even minor karyotypic variations. Thus, these three indices together increase the precision
of results in comparison with other existing methods. All this has important consequences as regards the interpretation of
the results of karyological studies. 相似文献
4.
This study focuses on karyological investigation of four taxa of Dianthus (Caryophyllaceae) including D. crossopetalus, D. orientalis subsp. stenocalyx, D. orientalis subsp. gorganicus, and Dianthus sp. distributed in Northeast of Iran. The karyotype asymmetry/symmetry was evaluated using two methods: 1) CVCL (coefficient of variation of chromosome length) and CVCI (heterogeneity of the centromeric index); and 2) MCA (mean centromeric asymmetry). The karyotype asymmetry was also used to investigate the relationships among the taxa. Results obtained from the current study revealed that there are two different ploidy levels (2n = 2x = 30 and 2n = 4x = 60) among the investigated taxa. The indices CVCL and MCA described karyotype asymmetry correctly based on variation in chromosome length. Diagram of CVCL vs. MCA seems to be appropriate for karyological delimitation and taxonomic relationships among the Dianthus taxa under study. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
6.
Mitotic chromosomes of 450 individuals, representing 59 accessions of 18 of the 22 species of Solanum sect. Basarthrum were studied. Statistical analyses of chromosome length, genome length, and centromere position yielded estimates of karyotype composition and asymmetry. A generalized karyotype of the section shows that most of the chromosomes are metacentric (44%) or submetacentric (53%). A general trend emerged: the greater the total genome length, the more asymmetric the karyotype. However, karyotype asymmetry does not seem to be based on major chromosomal rearrangements. There is variation in species groups in the karyotype formula, and chromosome length differences were useful in distinguishing series. Patterns of cytological variation reinforce the systematic arrangement of the taxa based on morphological, chemical, and molecular studies. Chromosomal differences characterize most of the species. Five species bear subtelocentric chromosomes, two have telocentrics, and two have satellites. The genomes of the staminate and pistillate plants of the dioecious S. appendiculatum are identical. Of the species proposed as progenitors of the domesticated cultigen S. muricatum, S. caripense is the most similar karyotypically. 相似文献
7.
以2份角堇与4份大花三色堇自交系为试验材料,采用染色体常规压片方法,观察和分析了它们的细胞染色体数目、相对长度、平均臂比等核型指标,以明确两种植物细胞学特点,为分类以及育种提供理论依据。结果表明:(1)2份角堇自交系染色体数目均为2n=2x=26,染色体基数为x=13,染色体核型公式分别为2n=2x=26=8m+12sm+6st、2n=2x=26=4m+16sm+6st,核型不对称系数为67.20%~70.10%,核型分类均属于3B。(2)4份大花三色堇自交系均为四倍体,其中2份(EYO-1-2-1-4、DSRFY-1-1-2)染色体数目为44,核型公式为2n=4x=44=4m+16sm+6st、2n=4x=44=16m+24sm+4st;2份(G10-1-3-1-4、XXL-YB-1-1-1-1)染色体数目为48,核型公式分别为2n=4x=48=8m+20sm+20st、2n=4x=48=4m+36sm+8st,核型不对称系数为66.74%~71.77%,核型分类属于2B、3B。 相似文献
8.
9.
In this study karyotypic features of the five species of the family Bufonidae from the central area of Argentina are described.
The species are Rhinella achalensis, Rhinella arenarum, Rhinella fernandezae, Rhinella schneideri and Melanophryniscus stelzneri. The metaphases were obtained from intestinal and testis cells, using conventional techniques. Twenty metaphasic figures
per individual were analyzed and the total length of each chromosome and the length of the four arms were measured. The obtained
measurements were processed using Excel 2000 to obtain the average length of the arms p and q, the arm ratio, the centromeric index, the relative chromosome length and the relative arm length. All species showed karyotype
2n = 22, and karyotype formula of 6: 5. Pairs one to six were large, with a relative chromosome length between 18.64–7.59%;
pairs seven to eleven were small, with a relative chromosome length between 7.18–2.42%. In all species the chromosome morphology
was metacentric or submetacentric. Karyotype and ideograms were made for all species, based on morphometric parameters of
the chromosome complement. Finally, discriminant analysis was used to separate the five species analyzed, with a highly significant
classification rate of 80% and P < 0.0001. These results agree, in general, with those presented by other authors, however, in M. stelzneri detailed karyological
studied have not been made so far, thus this work represents a significant contribution to the karyotypic decryption features
of this species and the Rhinellla species from central area of Argentina. 相似文献
10.
对青藏高原高山冰缘地区毛茛科3种特有植物的核型进行了分析。它们的核型公式(K)、染色体相对长度组成(C.R.L.)和核型不对称系数(As.K%)分别为:青藏金莲花Troliuspumilusvar.tanguticus:K(2n)=6m+8sm(2SAT)+2st,C.R.L.=4L+4M2+4M1+4S,As.K%=63.57,核型属2B型;甘青乌头Aconitumtanguticum为K(2n)=6m+10sm,C.R.L.=4L+8M1+4S,As.K%=62.54,2B型;单花翠雀花Delphiniumcandelabrumvar.monanthum为K(2n)=6m+8sm+2st,C.R.L.=4L+4M2+4M1+6S,As.K%=64.34,属3B型。经同相关近缘种核型资料比较,青藏金莲花核型不对称性和进化程度比金莲花T.chinensis低;甘青乌头的核型不对称性和进化程度在其近缘类群(乌头组Sect.Aconitum)已报道的种之内最低;单花翠雀花核型不对称性和进化水平比翠雀组(Sect.Delphinastrum)已报道的展毛翠雀花D.kamaoensevar.glabrescens、 相似文献
11.
With the help of Computer Aided Karyotyping procedures, Ag-NOR staining and C-banding techniques, the karyotype of Pyrrhopappus carolinianus (Asteraceae, Lactuceae) has been studied. The species has 2n=12 chromosomes. Silver staining reveals that the two shortest pairs of chromosomes possess NOR's. On the basis of chromosome length and centromere position, only the longest chromosome pair and the satellite chromosomes can be identified. Two types of C-banding can be obtained, dependent on the temperature of the hydrochloric acid hydrolysis of the root tips. Hydrolysis at 60°C results exclusively in centromeric bands, whereas a treatment at room temperature reveals a pattern of intercalary bands. A computer assisted analysis of the intercalary banding pattern resulted in the construction of schematic representation of the average C-banding pattern. This banding pattern allows an easy identification of each of the chromosome pairs. 相似文献
12.
S. E. Schlarbaum R. J. Rose E. Small Lowell B. Johnson 《Plant Systematics and Evolution》1989,166(1-2):69-78
Studies were made on the chromosome complements and chloroplast genomes ofMedicago lupulina andM. secundiflora, which comprise sectionLupularia ofMedicago. Both types of analyses indicated more substantial differences between these species than suggested by external morphology.Medicago lupulina has a relatively asymmetrical karyotype in terms of centromeric position and relative length. The karyotype ofM. secundiflora is comparatively more asymmetrical in centromeric position and reduced in absolute size but exhibits greater symmetry in relative length. The restriction endonuclease fragmentation patterns of the chloropiast DNA of these two species (with Bam HI, Eco RI, Bgl II, and Xho I) show little similarity, with only 17% of the fragments matching in size. The lack of interspecific congruence among data of morphology, karyology and cpDNA inLupularia is contrary to consistency exhibited among these data inMedicago subsect.Intertextae. 相似文献
13.
Karyological analysis of the genus Canna (Cannaceae) 总被引:1,自引:0,他引:1
Nobuyuki Tanaka H. Uchiyama H. Matoba T. Koyama 《Plant Systematics and Evolution》2009,280(1-2):45-51
Somatic chromosome numbers and karyological features in 22 taxa of the genus Canna (Cannaceae) were investigated and are presented here for the first time. The chromosome numbers were primarily reported for C. bangii, C. indica var. sanctae-rosae and C. tulianensis. A triploid somatic chromosome number of 2n = 27 was found only in C. discolor, while the remaining taxa were diploids with 2n = 18. Chromosome numbers are considered to be remarkably stable within the Cannaceae. Canna shows a symmetric karyotype that consists mostly of median chromosomes, but with some subterminal or submedian chromosomes, and a karyotype homogenous in variation in chromosome length. The karyotype of some taxa of Canna, furthermore, is characterized by median chromosomes with a secondary constriction in the centromeric region. Cytotaxonomical characteristics of the family Cannaceae and the related groups in the Zingiberales are discussed. 相似文献
14.
A new karyotypic procedure is described for tick chromosomes along with modifications of accepted techniques for C-banding and silver-staining. The staining procedures produce patterns with staining limited to the centromeric regions and the nucleolar organizer regions (NORs). The possible reasons for the concordant patterns are discussed based on the staining characteristics of the 2 techniques. The karyotype of Rhipicephalus sanguineus possesses 20 acrocentric autosomes with a single pair of NORs located proximal to the centromere on the largest autosomal pair. The sex-determining system is XX:XO with the X chromosome being the largest chromosome in the complement and subtelocentric. 相似文献
15.
Carbone L Nergadze SG Magnani E Misceo D Francesca Cardone M Roberto R Bertoni L Attolini C Francesca Piras M de Jong P Raudsepp T Chowdhary BP Guérin G Archidiacono N Rocchi M Giulotto E 《Genomics》2006,87(6):777-782
Centromere repositioning (CR) is a recently discovered biological phenomenon consisting of the emergence of a new centromere along a chromosome and the inactivation of the old one. After a CR, the primary constriction and the centromeric function are localized in a new position while the order of physical markers on the chromosome remains unchanged. These events profoundly affect chromosomal architecture. Since horses, asses, and zebras, whose evolutionary divergence is relatively recent, show remarkable morphological similarity and capacity to interbreed despite their chromosomes differing considerably, we investigated the role of CR in the karyotype evolution of the genus Equus. Using appropriate panels of BAC clones in FISH experiments, we compared the centromere position and marker order arrangement among orthologous chromosomes of Burchelli's zebra (Equus burchelli), donkey (Equus asinus), and horse (Equus caballus). Surprisingly, at least eight CRs took place during the evolution of this genus. Even more surprisingly, five cases of CR have occurred in the donkey after its divergence from zebra, that is, in a very short evolutionary time (approximately 1 million years).These findings suggest that in some species the CR phenomenon could have played an important role in karyotype shaping, with potential consequences on population dynamics and speciation. 相似文献
16.
为了探讨苦豆子(Sophora alopecuroides)不同居群的染色体核型特征及进化关系,采用染色体常规压片技术分析了分布于内蒙古、甘肃、宁夏等6个自然地理居群的核型特征和进化趋势。结果显示:苦豆子6个居群的染色体数目恒定,均为2n=2x=36;染色体类型有中部着丝粒(m)和近中部着丝粒(sm)2种,除甘肃武威的居群3含有sm型染色体外,其余居群的染色体均为m型;染色体平均臂比为1.19~1.37,长度比介于1.72~2.19,核型不对称系数处于54.30%~57.17%;核型类型有1A、3A和2B三种;苦豆子居群3的核型不对称系数最大,进化程度较高,居群19(内蒙古鄂尔多斯)的核型不对称系数最小,进化程度较低。聚类分析显示,苦豆子6个参试居群聚集成A和B两大分支,分支A又可分为C和D两亚支,其中居群5(甘肃武威)和居群13(内蒙古阿拉善盟)聚为C亚支,亲缘关系较近,居群3单独聚为D亚支,与C亚支两居群的亲缘关系相对较远;分支B又可分为E和F两亚支,居群19和居群43(内蒙古鄂尔多斯)聚为E亚支,亲缘关系较近,居群17(宁夏银川)单独聚为F亚支,与E亚支两居群的亲缘关系相对较远。本研究从居群水平上探讨了苦豆子的染色体数目、核型特征和进化趋势,为今后苦豆子系统进化和种质资源遗传多样性研究提供了细胞学证据。 相似文献
17.
The pachytene chromosomes of maize as revealed by fluorescence in situ hybridization with repetitive DNA sequences 总被引:13,自引:0,他引:13
C. C. Chen C. M. Chen F. C. Hsu C. J. Wang J. T. Yang Y. Y. Kao 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,101(1-2):30-36
A repetitive DNA sequence, ZmCR2.6c, was isolated from maize based on centromeric sequence CCS1 of the wild grass Brachypodium sylvaticum. ZmCR2.6c is 309 bp in length and shares 65% homology to bases 421–721 of the sorghum centromeric sequence pSau3A9. Fluorescence
in situ hybridization (FISH) localized ZmCR2.6c to the primary constrictions of pachytene bivalents and to the stretched regions
of MI/AI chromosomes, indicating that ZmCR2.6c is an important part of the centromere. Based on measurements of chromosome
lengths and the positions of FISH signals of several cells, a pachytene karyotype was constructed for maize inbred line KYS.
The karyotype agrees well with those derived from traditional analyses. Four classes of tandemly repeated sequences were mapped
to the karyotype by FISH. Repeats 180 bp long are present in cytologically detectable knobs on 5L, 6S, 6L, 7L, and 9S, as
well as at the termini and in the interstitial regions of many chromosomes not reported previously. A most interesting finding
is the presence of 180-bp repeats in the NOR-secondary constriction. TR-1 elements co-exist with 180-bp repeats in the knob
on 6S and form alone a small cluster in 4L. 26S and 5S rRNA genes are located in the NOR and at 2L.88, respectively. The combination
of chromosome length, centromere position, and distribution of the tandem repeats allows all chromosomes to be identified
unambiguously. The results presented form an important basis for using FISH for physical mapping and for investigating genome
organization in maize.
Received: 29 June 1999 / Accepted: 10 November 1999 相似文献
18.
The karyotypes of four gerreids of the western Atlantic Ocean are documented. A diploid chromosome complement of 48 telocentric chromosomes was found in the four species (2N=48t, fundamental number FN=48). No differences were detected either in the number of chromosomes of the standard karyotype, in their karyotype size, or between the karyotypes derived from male or female specimens of any of the species. Chromosome length decreased progressively and slightly from pair 1 to pair 24. The Ag–NOR karyotypes of E. argenteus and E. harengulus were characterized by the position of the nucleolar organizer regions next to the centromere in chromosome pair 1, whereas in E. gula and E. plumieri Ag–NORs were detected in pair 4. The other 46 chromosomes showed a light staining of the centromere with no terminal or intermediate heterochromatic blocks. All Eucinostomus species showed Ag–NORs of similar size, while Eugerres plumieri showed Ag–NORs 10–20% larger than Eucinostomus species. A combination of size and position of the Ag–NORs identified E. gula, while size alone identified E. plumieri. However, the ancestral state for size and position of Ag–NORs could not be established. There was no differential staining of the chromosomes by G-banding. The karyotype of the gerreids appears similar to the hypothetical ancestral karyotype of fish. The phylogenetic relationships among these species could not be established because of the lack of chromosome G-bands. Most likely this indicates a homogeneous distribution of GC nucleotides in the chromosomes. 相似文献
19.
为了解扇脉杓兰(Cypripedium japonicum Thunb.)和无距虾脊兰(Calanthe tsoongiana T. Tang et F. T. Wang)的核型,采用根尖压片法对扇脉杓兰和无距虾脊兰的染色体数目和核型进行了研究。结果表明,扇脉杓兰体细胞的染色体数为22,核型公式为2n=2x=22=16m+2sm+2st+2t,染色体相对长度组成为2n=22=2L+6M2+12M1+2S,核不对称系数为60.01%,核型分类为2B型;而无距虾脊兰体细胞的染色体数为40,核型公式为2n=2x=40=28m+10sm+2st,染色体相对长度组成为2n=40=8L+10M2+16M1+6S,核不对称系数为59.84%,核型分类为2B型;两者核型都较为对称。其中,无距虾脊兰的核型为首次报道。这为扇脉杓兰和无距虾脊兰的进化地位和种质保护提供了细胞学证据。 相似文献
20.
Teodora Mutafova 《Systematic parasitology》1994,28(3):229-238
The morphometric characteristics of the chromosomes and the variability of the C-heterochromatin blocks in the trematodes Echinoparyphium aconiatum, E. recurvatum, Echinostoma revolutum, E. echinatum, Hypoderaeum conoideum, Isthmiophora melis, Paryphostomum radiatum, Neoacanthoparyphium echinatoides, Plagiorchis maculosus and Opisthioglyphe ranae are determined. The terminal and subterminal localisation of the centromere is a characteristic of the taxa examined. Typical two-arm chromosomes are rare. The karyotype of the examined trematodes is asymmetrical, and this asymmetry is a result of differences in the lengths of the chromosome arms. It is proved that the regression of the lengths of the chromosome arms has a linear character with a similar angle of slope in the different species. Centric fusion and unreciprocal translocations are accepted as contributing significantly to chromosome changes. A hypothesis on the possible mechanism of chromosome changes in the trematode karyotype is proposed. 相似文献