Comparison of the Giemsa C-banded and N-banded karyotypes of twoElymus species,E. dentatus andE. glaucescens (Poaceae: Triticeae)

The karyotypes ofElymus dentatus from Kashmir andE. glaucescens from Tierra del Fuego, both carrying genomesS andH, were investigated by C- and N-banding. Both taxa had 2n = 4x = 28. The karyotype ofE. dentatus was symmetrical with large chromosomes. It had 18 metacentric, four submetacentric and six satellited chromosomes. The karyotype ofE. glaucescens resembled that ofE. dentatus, but a satellited chromosome pair was replaced by a morphologically similar, non-satellited pair. The C-banding patterns of both species had from one to five conspicuous and a few inconspicuous bands per chromosome. N-banding differentiated the chromosomes of the constituent genomes by producing bands in theH genome only. TheS genomes of both species were similar with five metacentric and two satellited chromosomes having most conspicuous C-bands at telomeric and distal positions. They resembled theS genome of the genusPseudoroegneria. TheH genomes had four similar metacentric and two submetacentric chromosomes. The seventhH genome chromosome ofE. dentatus was satellited, that ofE. glaucescens nonsatellited, but otherwise morphologically similar. The C-bands were distributed at no preferential positions. TheH genome ofE. dentatus resembles theH genomes of some diploidHordeum taxa.     

Electrophoretic karyotypes of some related Mucor species

Contour clamped homogeneous electric field (CHEF) gel electrophoresis was used to obtain electrophoretic karyotypes from nine Mucorstrains representing five different species (M. bainieri, M. circinelloides, M. mucedo, M. plumbeus and M. racemosus). The chromosomal banding patterns revealed high variability among the isolates. The sizes of the DNA in the Mucor chromosomes were estimated to be between 2.5 and 8.7 Mb. The total genome sizes were calculated to be between 30.0 and 44.7 Mb. The applicability of these electrophoretic karyotypes for the investigation of genome structure, for strain identification and for species delimitation is considered.     

Giemsa C-banded karyotypes of some diploidArtemisia species

Detailed C-banded karyotypes of eight diploidArtemisia species from three different sections are reported together with preliminary observations on three additional related diploid species. In the majority, the overall amount of banding is relatively low. Bands are mostly confined to distal chromosome regions; intercalary banding is virtually absent and centromeric heterochromatin is also scarce. With the exception ofA. judaica there is in general great uniformity in karyotype structure but considerable interspecific variation in total karyotype length (and hence DNA content) ranging from 44 µm inA. capillaris (2n = 18) to 99 µm inA. atrata (2n = 18).A. judaica (2n = 16; total karyotype length 97 µm) was distinguished by its karyomorphology, with one large non-banded metacentric chromosome pair and 7 pairs of smaller terminally banded meta- or submetacentric chromosomes.     

车前属两种植物的核型研究

本文对我国两种车前属Ｐｌａｎｔａｇｏ植物的核型进行了分析。２个种的染色体数目均为２ｎ＝２ｘ＝１２。它们的核型是：海滨车前Ｐ．ｃａｍｔｓｃｈａｔｉｃａＬｉｎｋ,Ｅｎｕｍ．２ｎ＝２ｘ＝１２＝８ｍ＋４ｓｍ;毛车前Ｐ．ｊｅｈｏｈｌｅｎｓｉｓＫｏｉｄｚ．２ｎ＝２ｘ＝１２＝６ｍ＋４ｓｍ＋２ｓｔ。它们的核型均属“２Ａ”型。由１２条染色体组成。     

五种棺头蟋核型的比较研究

报道了中国5种棺头蟋的核型：石首棺头蟋Loxoblemmus equestris, 2n=17, XO(♂);小棺头蟋L. aomoriensis, 2n=11, XO(♂); 哈尼棺头蟋L. haani, 2n=11, XO(♂);多伊棺头蟋L. doenitzi, 2n=11, XO(♂)和窃棺头蟋L. detectus, 2n=11,XO(♂)。并应用核型似近系数及进化距离对这5种蟋蟀作了聚类分析,得出5种蟋蟀的演化方向为石首棺头蟋→小棺头蟋→哈尼棺头蟋→多伊棺头蟋→窃棺头蟋。     

Localization of NORs in karyotypes of four Rana species

NORs were localized by Ag-AS-staining in karyotypes of Rana nigromaculata, R. macrocnemis, R. latastei (2n=26) and R. chensinensis, 2n=24. As in the majority of other Rana species, the NORs are located in the long arms of the 10th (or 11th in R. chensinensis) chromosome pair. The presence of a second secondary constriction in R. latastei, as reported earlier, was not confirmed.     

Electrophoretic karyotypes and chromosome numbers in Candida species

The electrophoretic karyotypes of five Candida albicans isolates and of five other Candida species have been determined, using orthogonal field alternating gel electrophoresis (OFAGE). None of the C. albicans isolates had the same electrophoretic karyotype. By comparing all five strains, we arrived at a chromosome number of nine to ten, but since the organism is diploid, we cannot distinguish genetically different chromosomes from homologues which resolve. We determined minimal chromosome numbers of 9 for Candida stellatoidea, 10 for C. glabrata and 6 for C. guilliermondii.     

Heterochromatins and band karyotypes in three species of salmonids

Summary The heterochromatins of rainbow trout (Salmo gairdneri R.), brown trout (Salmo trutta fario L.) and brook trout (Salvelinus fontinalis M.) were characterized by sequential chromomycin A₃/distamycin A/DAPI (CDD) and DAPI/actinomycin D (DAPI/AmD) fluorescence. On most biarmed chromosomes, an equilocal localization of prominent DAPI/AmD positive, chromomycin A₃ negative, AT-rich blocks at the centromeres were observed in all three species. Band karyotypes of the three species were established. In rainbow trout, several DAPI/AmD positive heterochromatin blocks behaved positive in a silver-staining method. Mitotic and interphase studies proved the presence of inter-individual NOR variation in brown trout. The NORs of brook trout were localized on chromosomes 5, 10, 14, 15 and 29.     

甘草属2种植物的核型研究

用光学显微镜观察了豆科(Leguminosae)甘草属(Glycyrrhiza)2种荒漠植物的染色体,研究结果表明,黄甘草(G.eurycarpa P.C.Li)、腺荚甘草(G．korshinskii G．Grig)的体细胞染色体数目均为2n＝16,核型公式2n＝2x＝16＝16m,属于Stebbins核型的“lA”型。     

4种国产兰属植物的核型比较研究

首次报道了4种国产兰属植物建兰（C.ensifolium(L.)Sw.)。墨兰（C.sinense(Jacksn ex Andr.)Willd.),珍珠矮（C.nanulum Y.S.Wu et S.C.Chen),兔耳兰（C.lancifolium Hook)的核型比较研究结果。具体如下：兔耳兰为2n=2x=38=28m 8sm 2st(2SAT),核不对称系数为61．22％,2A型;建兰的核型公式为2n=2x=40=30m 10sm(2SAT),核不对称系数为59．15％,2B型,墨兰的核型公式为2n=2x=40=28m 10sm 2st,核不对称系数为59．83％,2B型,珍珠矮为2n=2x=40=26m 10sm 4st,核不对称系数为62．24％,2B型。结合兰属植物若干稳定特化的形态学特征,讨论了兰属植物的核型进化。     

Chromosome numbers and karyotypes of Catasetum species (Orchidaceae)

Mitotic chromosomes of 12 species of Catasetum were assessed to contribute with the karyotypic study of the subtribe Catasetinae (Orchidaceae), expanding the knowledge of this group in terms of chromosomes and supporting its taxonomic and evolutionary analysis. The species are maintained in cultivation in the greenhouse of the Department of Plant Biology/IB/UNICAMP and in the “Orquidário Frederico Carlos Hoehne” of the Botanical Garden of São Paulo. Chromosome counts ranged from 2n = 54 to 2n = 108. Karyotypes were prepared for all species studied, in which there was a predominance of metacentric chromosomes and some submetacentric ones. The chromosome size ranged from 0.5 to 4.9 μm, the total chromosome length ranged from 34.7 to 78.7 μm and the asymmetry index TF% ranged from 21.2 to 42.3. The results obtained so far favor the taxonomy of the genus, allowing to distinguish species with very similar external morphology.     

C-banded karyotypes of two Silene species with heteromorphic sex chromosomes.

Mitotic metaphase chromosomes of Silene latifolia (white campion) and Silene dioica (red campion) were studied and no substantial differences between the conventional karyotypes of these two species were detected. The classification of chromosomes into three distinct groups proposed for S. latifolia by Ciupercescu and colleagues was considered and discussed. Additionally, a new small satellite on the shorter arm of homobrachial chromosome 5 was found. Giemsa C-banded chromosomes of the two analysed species show many fixed and polymorphic heterochromatic bands, mainly distally and centromerically located. Our C-banding studies provided an opportunity to better characterize the sex chromosomes and some autosome types, and to detect differences between the two Silene karyotypes. It was shown that S. latifolia possesses a larger amount of polymorphic heterochromatin, especially of the centromeric type. The two Silene sex chromosomes are easily distinguishable not only by length or DNA amount differences but also by their Giemsa C-banding patterns. All Y chromosomes invariably show only one distally located band, and no other fixed or polymorphic bands on this chromosome were observed in either species. The X chromosomes possess two terminally located fixed bands, and some S. latifolia X chromosomes also have an extra-centric segment of variable length. The heterochromatin amount and distribution revealed by our Giemsa C-banding studies provide a clue to the problem of sex chromosome and karyotype evolution in these two closely related dioecious Silene species.     

国产毛茛属三种植物的核型研究

对国产三种毛茛属 (Ranunclus)植物进行了核型研究 ,其中昆明毛茛 (RanunculuskunmingensisW .T .Wang)染色体数目 2n=1 4及核型 2n =1 4 =6m +4sm +4st为首次报道 ;匍枝毛茛 (R .repenceL .)核型公式为 2n =4x =3 2 =8m +1 2sm +1 0st+2t,它是由两个不同的染色体组组成 ;刺果毛茛 (R .muricatusL .)核型公式为 2n=8x=64=1 0m +2 2sm +2 8st+4t,它也是由两个不同的染色体组组成     

Elimination of altered karyotypes by sexual reproduction preserves species identity.

Resolving the persistence of sexual reproduction despite its overwhelming costs (known as the paradox of sex) is one of the most persistent challenges of evolutionary biology. In thinking about this paradox, the focus has traditionally been on the evolutionary benefits of genetic recombination in generating offspring diversity and purging deleterious mutations. The similarity of pattern between evolution of organisms and evolution among cancer cells suggests that the asexual process generates more diverse genomes owing to less controlled reproduction systems, while sexual reproduction generates more stable genomes because the sexual process can serve as a mechanism to "filter out" aberrations at the chromosome level. Our reinterpretation of data from the literature strongly supports this hypothesis. Thus, the principal consequence of sexual reproduction is the reduction of drastic genetic diversity at the genome or chromosome level, resulting in the preservation of species identity rather than the provision of evolutionary diversity for future environmental challenges. Genetic recombination does contribute to genetic diversity, but it does so secondarily and within the framework of the chromosomally defined genome.     

On the karyotypes of the Neorhabdocoela species and karyological evolution of Turbellaria

The karyotypes of 10 species belonging to the Neorhabdocoela order (Turbellaria) are described: Proxenetes flabelliger, 2n=6 (Trigonostomidae), Promesostoma rostratum, 2n=12 (Promesostomatidae), Castrada sp., 2n=6, Rhynchomesostoma rostratum, 2n=6, Bothromesostoma esseni, 2n=10, Mesostoma lingua, 2n=8 (Typhloplanidae), Provortex karlingi, 2n=8 (Provorticidae), Halamovortex macropharynx, 2n=16 (Dalyellidae), Macrorhynchus crocea, 2n=16, and Gyratrix hermaphroditus, 2n=4 (Polycystidae). It is proposed that the karyotypes of the ancestral marine neorhabdocoel forms, as well as those of the other groups of turbellarians, must have consisted of 16–20 biarmed chromosomes. The processes of adaptation and speciation in each group seem to be accompanied by a gradual decrease in chromosome number to 2n=8–4, this being due to Robertsonian fusions and translocations. In some freshwater turbellarians the diploid number increased by polyploidisation. The same processes evidently took place in different groups of parasitic worms.     

The karyotypes of Dugesia species from Spain (Turbellaria,Tricladida)

Some species of Planarians, new to Spain, are recorded. Dugesia polychroa, D. sicula, D. iberica and D. gonocephala s. 1. have been investigated karyologically. The former possesses a diploid complement characteristic of the biotype A (2n = 8); the second is diploid with 2n = 18; diploidy and triploidy were found in sexual populations of D. iberica with n = 8. Triploidy occurred in all the asexual strains of the D. gonocephala group with a basic number of either 8 or 9. In this latter case B-chromosomes were occasionally found.     

Banded karyotypes of 20 Papionini species reveal no necessary correlation with speciation

The G-banded karyotypes of 20 species of the tribe Papionini are remarkably similar, and the amount of phylogenetic interpretation permitted is limited. The genera Mandrillus and Cercocebus may be linked by a derived chromosome 10. T. gelada may be linked to the macaques by chromosome 2. Chromosome 5, which differs in M. fascicularis, makes this species an unlikely ancestor of the Sulawesi (Celebes) macaques. An alternate hypothesis, which takes into consideration the possibility that ancestral populations may be polymorphic for these chromosome variants, suggests that different chromosome variants have become fixed in different lines. These chromosomes would therefore not reflect phylogenetic relations. In the Papionini the karyotype has not played a major role in diversification and speciation.     

Constitutive heterochromatin variation in two species of rattus with apparently similar karyotypes

Rattus blanfordi and R. cutchicus medius both have a chromosome complement of 2n=36 and all chromosomes except the submetacentric Y of R. blanfordi are acrocentric. The apparently similar karyotypes of the two species, however, show variations in the nature and quantity of C-band-positive constitutive heterochromatin (C-heterochromatin) as revealed by C- and G-banding and Hoechst 33258 fluorescence. R. blanfordi with large-sized X and Y chromosomes and conspicuously larger centromeric heterochromatin in all the autosomes as compared to that of R. cutchicus medius has much more C-heterochromatin in its genome than the latter. The variation in the quantity of C-heterochromatin has been accomplished without altering the morphology of the acrocentric chromosomes unlike other mammals in which variations have been reported to result generally in the addition or deletion of a totally heterochromatic second arm.