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  • 1
    Electronic Resource
    Electronic Resource
    A sequential analysis of meiosis in the male mouse using a restricted spermatocyte population obtained by a hydroxyurea/triaziquone treatment (1979)
    Springer
    Chromosoma 71 (1979), S. 237-248 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A method is described to restrict the spermatocyte population in mice and other rodents using hydroxyurea (HU) and triaziquone (T). HU affects cells in S-phase, whereas T is an agent especially active on spermatogonia and not on spermatocytes. An application of three i.p. HU injections with 12 h intervals, followed about nine days later by one i.p. T injection creates two large gaps in the spermatogenic line. The two gaps enclose a small, well-defined group of primary spermatocytes in meiotic interphase. — The development of the restricted spermatocyte population is followed day by day. The analysis of meiosis in male mice has revealed the correct sequence of meiotic, and especially prophase I stages. On account of clearly visible differences in chromosome morphology the diplotene stage could be divided into three periods. It is suggested to use the following nomenclature: pre-diffuse diplotene, diffuse diplotene and post-diffuse diplotene. The experiment was also informative about the timing of the stages in spermatocyte development by correlating the days at which the successive stages were observed with the corresponding stage of the epithelial cycle. The calculation of the position and duration of the diffuse diplotene, enables us to put forward a proposal about the significance of the diffuse diplotene. — A combination of the HU/T method with cell separation techniques provides good perspectives for detailed biochemical studies on processes taking place during meiosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292826
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  • 2
    Electronic Resource
    Electronic Resource
    Synaptonemal complex pairing and metaphase I association in a telo-substituted telotrisomic of rye (Secale cereale L.) (1988)
    Springer
    Chromosoma 97 (1988), S. 88-95 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The synaptonemal complexes in pollen mother cells (PMCs) of rye in which one chromosome 1R was replaced by the two corresponding telocentrics, and where one additional telocentric 1RS was present, showed approximately the expected 2∶1 ratio of 1R-1RL-1RS trivalent with 1RS univalent versus heteromorphic 1R-1RL bivalent with 1RS bivalent. In addition, however, many cells with a partner exchange were found, several even including bivalents other than 1R. At metaphase I1R-1RL-1RS trivalents predominated, cells with two univalent telocentrics were relatively frequent but partner exchange configurations were extremely rare. It is concluded that the almost consistent failure to form chiasmata in the interstitial region of 1RS after partner exchange, combined with much more frequent chiasma formation in the terminal segment, is the main reason for the unexpected metaphase I configuration frequencies. Possible causes are discussed. The shift observed does not yet explain the erratic variation in relative frequencies of metaphase I configurations reported earlier in similar material. Frequent pairing partner exchange may play a role there also.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331798
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  • 3
    Electronic Resource
    Electronic Resource
    Computerized analysis of chromosomal parameters in karyotype studies (1987)
    Springer
    Theoretical and applied genetics 73 (1987), S. 630-634 
    Details
    ISSN: 1432-2242
    Keywords: Karyotype ; Automated analysis ; Chromosome measurement ; Computer ; Cytogenetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A study is presented of the possibilities and limitations of semi-automated karyotype analysis on the basis of chromosome length and centromere index. A number of computer programs have been developed for 1) quick and precise measurements of chromosome arm length with the help of a graphics tablet, 2) computing (relative) length and centromere index and statistical analyses of the data, and 3) representation of these chromosomal parameters in two-dimensional scattergrams. An ellipse representing 95% of the probability mass is drawn around the bivariate mean of each chromosome. The size and orientation of the axes are calculated from repeated measurements of the chromosomes of one metaphase plate. If there is a correlation between length and centromere index, which is often the case, the axes of the ellipse are tilted. Incorporation of such a covariance analysis proved to be of great importance for an accurate karyotype analysis. The “Computer Aided Karyotyping” package does not contain routines for an automated classification of the chromosomes. The main reason is that the variation in length and centromere index of a given chromosome in different cells is often much larger than the variation between nonhomologous chromosomes. In addition, it was our aim to develop universal karyotyping aids which can be used regardless of the species studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260769
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  • 4
    Electronic Resource
    Electronic Resource
    FISH to meiotic pachytene chromosomes of tomato locates the root-knot nematode resistance gene Mi-1 and the acid phosphatase gene Aps-1 near the junction of euchromatin and pericentromeric heterochromatin of chromosome arms 6S and 6L, respectively (1999)
    Springer
    Theoretical and applied genetics 98 (1999), S. 365-370 
    Details
    ISSN: 1432-2242
    Keywords: Key words Fluorescence in situ hybridisation FISH ; Pachytene chromosomes ; Nematode resistance gene ; Mi ; Tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The root-knot nematode resistance gene Mi-1 in tomato has long been thought to be located in the pericentromeric heterochromatin region of the long arm of chromosome 6 because of its very tight genetic linkage (approx. 1 cM) to the markers Aps-1 (Acid phosphatase 1) and yv (yellow virescent). Using Mi-BAC clones and an Aps-1 YAC clone in fluorescence in situ hybridisation (FISH) to pachytene chromosomes we now provide direct physical evidence showing that Mi-1 is located at the border of the euchromatin and heterochromatin regions in the short arm (6S) and Aps-1 in the pericentromeric heterochromatin of the long arm (6L) close to the euchromatin. Taking into account both the estimated DNA content of hetero- and euchromatin regions and the compactness of the tomato chromosomes at pachytene (2 Mb/μm), our data suggest that Mi-1 and Aps-1 are at least 40 Mb apart, a base pair-to-centiMorgan relationship that is more than 50-fold higher than the average value of 750 kb/cM of the tomato genome. An integrated cytogenetic-molecular map of chromosome 6 is presented that provides a framework for physical mapping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220051081
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  • 5
    Electronic Resource
    Electronic Resource
    Variation and geographical distribution of ploidy levels inPennisetum sectionBrevivalvula (Poaceae) in Burkina Faso, Benin and southern Niger (1995)
    Springer
    Plant systematics and evolution 198 (1995), S. 89-100 
    Details
    ISSN: 1615-6110
    Keywords: Poaceae ; Pennisetum sect.Brevivalvula ; Polyploidy ; apomixis ; flow cytometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pennisetum sect.Brevivalvula is a species complex characterized by polyploidy and apomixis. Ploidy level was assessed by DAPI-flow cytometry for 304 plants of the section, originating from Burkina Faso, Benin and southern Niger. The results were confirmed for 54 plants based on chromosome counts. The samples show four euploidy levels (with x = 9) distributed among five species:P. hordeoides (2n = 36, 54),P. pedicellatum (2n = 36, 45, 54),P. polystachion (2n = 18, 36, 45, 54),P. setosum (2n = 54), andP. subangustum (2n = 18, 36, 54). The geographical distribution of these ploidy levels seems related to major vegetation zones present in Africa. Diploid populations ofP. polystachion andP. subangustum were found in the Banfora area, in Burkina Faso.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00985108
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  • 6
    Electronic Resource
    Electronic Resource
    Chromosome banding patterns in Lettuce species (Lactuca sect.Lactuca, Compositae) (1993)
    Springer
    Plant systematics and evolution 185 (1993), S. 249-257 
    Details
    ISSN: 1615-6110
    Keywords: Compositae ; Lactuca sect.Lactuca ; Lactuca sativa ; L. serriola ; L. saligna ; L. virosa ; Chromosome banding ; karyotype evolution ; C-banding ; N-banding ; Ag-NOR staining
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chromosome banding patterns obtained with C- and N- banding, and AgNO3 staining were studied in somatic metaphase complements of fourLactuca species.L. sativa andL. serriola have almost identical chromosome morphology, andL. saligna differs only slightly from them, butL. virosa is quite distinct from the other species. A gross comparison of the banded karyotypes suggests a closer relationship ofL. saligna toL. sativa/serriola than toL. virosa. Our data agree with the results of previous crossing experiments in these species but conflict partly with recent RFLP data which indicate a closer phenetic relationship ofL. saligna toL. virosa than toL. sativa/serriola. Such a discrepancy may be explained assuming that domestication ofL. sativa/serriola resulted in an increased selection pressure on unique DNA sequences as demonstrated by the RFLP data. Differential evolution of specific heterochromatin classes (and presumably of highly repetitive DNA classes), as revealed by chromosome banding techniques was not linked to domestication. Thus the disparity in conclusions about relationship (in terms of genetic similarity) as based on the different experimental approaches reflects a non-parallel evolution of highly repetitive vs. unique DNA classes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00937661
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  • 7
    Electronic Resource
    Electronic Resource
    Quantification of total genomic DNA and selected repetitive sequences reveals concurrent changes in different DNA families in indica and japonica rice (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 388-394 
    Details
    ISSN: 1617-4623
    Keywords: Key words Repetitive sequences ; Oryza sativa L. ; indica rice ; japonica rice ; Genome size
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper describes a fluorescence in situ hybridization (FISH) analysis of three different repetitive sequence families, which were mapped to mitotic metaphase chromosomes and extended DNA fibers (EDFs) of the two subspecies of rice (Oryza sativa), indica and japonica (2n=2x=24). The repeat families studied were (1) the tandem repeat sequence A (TrsA), a functionally non-significant repeat; (2) the [TTTAGGG]n telomere sequence, a non-transcribed, tandemly repeated but functionally significant repeat; and (3) the 5S ribosomal RNA (5S rDNA). FISH of the TrsA repeat to metaphase chromosomes of indica and japonica cultivars revealed clear signals at the distal ends of twelve and four chromosomes, respectively. As shown in a previous report, the 17S ribosomal RNA genes (17S rDNA) are located at the nucleolus organizers (NORs) on chromosomes 9 and 10 of the indica cultivar. However, the japonica rice lacked the rDNA signals on chromosome 10. The size of the 5S rDNA repeat block, which was mapped on the chromosome 11 of both cultivars, was 1.22 times larger in the indica than in the japonica genome. The telomeric repeat arrays at the distal ends of all chromosome arms were on average three times longer in the indica genome than in the japonica genome. Flow cytometric measurements revealed that the nuclear DNA content of indica rice is 9.7% higher than that of japonica rice. Our data suggest that different repetitive sequence families contribute significantly to the variation in genome size between indica and japonica rice, though to different extents. The increase or decrease in the copy number of several repetitive sequences examined here may indicate the existence of a directed change in genome size in rice. Possible reasons for this phenomenon of concurrent evolution of various repeat families are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380051182
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  • 8
    Electronic Resource
    Electronic Resource
    Use of haploids of Beta vulgaris L. for the study of orcein and giemsa stained chromosomes (1978)
    Springer
    Euphytica 27 (1978), S. 41-47 
    Details
    ISSN: 1573-5060
    Keywords: Beta vulgaris ; sugar beet ; haploid ; C-banding ; idiogram ; chromosome identification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Some haploids isolated among the progeny from crosses involving several genotypically different motherplants of Beta vulgaris L., were used for an investigation on chromosome morphology of the genus Beta. The length of both the long and short arms proved to vary considerably for each chromosome, so that a representative idiogram of the 9 chromosomes could not be made. Staining the chromosomes according to the BSG-technique revealed only bands in the centromere regions. However, one chromosome with a narrow band in the short arm could be identified, which was supposed to be the nucleolar chromosome. The C-bands presumably correlate with the heterochromatic blocks as observed in mitotic and meiotic (pachytene) prophase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039118
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  • 9
    Electronic Resource
    Electronic Resource
    Transfer of resistance to beet cyst nematode from Beta patellaris to sugar beet (1983)
    Springer
    Euphytica 32 (1983), S. 287-298 
    Details
    ISSN: 1573-5060
    Keywords: Beta vulgaris ; sugar beet ; mangold ; Beta patellaris ; Beta maritima ; monosomic additiou ; meiosis ; Heterodera schachtii ; beet cyst nematode
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The chromosome bearing the gene(s) for resistance to the beet cyst nematode (Heterodera schachtii Schm.), could be transferred from Beta patellaris to B. vulgaris by interspecific hybridization and repeated backcrossing. A tetraploidized B. vulgaris originating from Anatolia (Turkey) was used as an intermediate. After several backcrosses with a number of different tetraploid and diploid beet cultivars, monosomic additions could be obtained which had the resistance bearing chromosome of B. patellaris. Cytological techniques were used for the study of this chromosome in resistant hybrids and monosomic additions. The analysis of pairing behaviour of the B. patellaris chromosome was hampered by the occurrence of non-specific stickiness of the chromosomes in meiocytes at pachytene and diakinesis. Moreover, the nature of resistance in monosomic additions was studied in growth cabinet experiments, revealing that the penetration rates of the larvae into the root system did not differ from the susceptible control plants. Among the F1B6 and F1B7 backcross derivatives, no plants with intermediate levels of resistance were found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00021437
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  • 10
    Electronic Resource
    Electronic Resource
    A standard karyogram of Petunia hybrida hort (1973)
    Springer
    Genetica 44 (1973), S. 474-484 
    Details
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An improved technique, viz., maceration with cellulase and pectinase, was applied in order to obtain chromosome preparations of botanical material suitable for fluorescence microscopy. The application of this method to Petunia hybrida allows the individual distinction of all chromosomes in mitosis. The following three criteria are required for this distinetion: the centromere index, the relative length, and the fluorescence intensity pattern after staining with Quinacrine. A standard karyogram is drawn up to render possible a comparison with other Petunia material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00161319
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