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  • 1
    Electronic Resource
    Electronic Resource
    Synaptonemal Complex and Chromosome Structure (1975)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Genetics 9 (1975), S. 91-109 
    Details
    ISSN: 0066-4197
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.ge.09.120175.000515
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  • 2
    Electronic Resource
    Electronic Resource
    Reconstruction of the Neurospora crassa pachytene karyotype from serial sections of synaptonemal complexes (1972)
    Springer
    Chromosoma 36 (1972), S. 119-130 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Serial sections from isolated asci were used to reconstruct the seven pachytene bivalents of Neurospora crassa. The synaptonemal complex could be traced for its whole length in each bivalent, being attached to the nuclear envelope at both ends in six. The satellite end of the nucleolar chromosome did not appear to be attached to the nuclear envelope. The estimated lengths of the bivalents ranged from 10.7 to 5.1 microns in one nucleus, from 11.5 to 4.2 microns in another, and from 8.5 to 4.4 microns in a third, with total haploid complement lengths of 45.5 microns, 47.3 microns, and 43.9 microns respectively. These values are considerably smaller than published light microscopical measurements.—The synaptonemal complex in N. crassa, as in other ascomycetes, has two banded ca. 400 Å wide lateral components held about 1200 Å apart by a central region containing the ca. 200 Å wide central component. With normal glutaraldehyde/OsO4-phosphate buffered fixation the chromatin of the pachytene bivalents is poorly contrasted. Occasional local thickenings of the central component into electron dense nodes ca. 1000 × 500 Å in longitudinal section are characteristic of the complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00285207
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrastructural analysis of maize pachytene karyotypes by three dimensional reconstruction of the synaptonemal complexes (1973)
    Springer
    Chromosoma 43 (1973), S. 145-176 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Aldehyde fixation followed by staining with phosphotungstic acid produces differential contrast between the synaptonemal complex and the chromatin of maize pachytene bivalents. Centromeres, heterochromatic knobs and large chromomeres are easily recognised. With this and other staining techniques the nucleolus organizer region can be differentiated into two components. — Microsporocyte nuclei at pachytene were serially sectioned and all ten bivalents reconstructed in five nuclei. An idiogram was derived from the mean chromosome (= synaptonemal complex) lengths, the arm ratios, positions of knobs and the nucleolus organizer region. The idiogram agrees well with that published from light microscopic analyses. However, bivalent lengths are only two thirds of those observed by light microscopy of squash preparations. Many telomeres of the bivalents are connected via chromatin to the nuclear envelope, but a varying number of free bivalent ends are observed in all five reconstructed nuclei. — Bivalents heterozygous for inversion 3b were reconstructed. In the presence of abnormal chromosome 10 (K10) the lateral components of the synaptonemal complex of chromosome 3 formed a typical inversion loop, while in one of the nuclei having no K10 the two lateral components of the long arms of chromosome 3 remained unpaired in the region of inversion heterozygosity. The presence of K10, which increases crossing-over frequencies and promotes intimate pairing at the light microscopic level, was thus found to permit formation of complete synaptonemal complexes in the inverted region. The extra terminal portion of the K10 chromosome folded back on itself and formed a morphologically normal synaptonemal complex in this — possibly non-homologously paired — region. The chromatin of centromeres and knobs from different bivalents were sometimes found to fuse, but the synaptonemal complexes transversing the fused centromeres or knobs retained their individuality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00483376
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  • 4
    Electronic Resource
    Electronic Resource
    Electron microscopy of spread maize pachytene synaptonemal complexes (1981)
    Springer
    Chromosoma 83 (1981), S. 575-591 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The Counce-Meyer microspreading technique for animal synaptonemal complexes (SCs) has been adapted to allow spreading of the SCs of maize pachytene microsporocytes for examination in the electron microscope (EM). The spread nuclei were well dispersed and flattened, and unstained SCs could be seen with light microscope (LM) phase optics. After PTA or ammoniacal silver staining, the SCs and kinetochores were readily recognized in the EM. Variable degrees of asynapsis, stretching of the SCs, and nonhomologous synapsis of lateral elements were noted, and cases of interlocking of lateral elements or SCs were not uncommon. Distinct lens-shaped thickenings of one or both lateral elements were observed at numerous sites along the SC in most nuclei. — The yield of well spread, complete nuclei, although not high, was sufficient to allow karyotypes to be prepared, based on relative SC lengths and arm ratios. The karyotypes agreed well with published EM and LM determinations, establishing the accuracy of the spreading technique for maize. However, considerable variation in absolute lengths of the SCs was noted. To evaluate the utility of the technique for cytogenetic investigations, two paracentric inversions, and two reciprocal translocations were spread and examined in the EM. The breakpoints estimated from measurements of spread SCs were in agreement with LM determinations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328521
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  • 5
    Electronic Resource
    Electronic Resource
    Medicago murex with 2n=16 and 2n=14 chromosome complements (1970)
    Springer
    Chromosoma 30 (1970), S. 109-122 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Contrary to the generally held view, M. murex Willd. was found to be of 2n=14 constitution in the great majority of accessions. The 2n= 16 type, though distributed sparsely over a wide area, is most likely a relic. Chromosome studies at pachytene indicate that the 2n=14 type probably arose from the 2n=16 type by translocation of the chromosomal material of the smallest chromosome in the 2n=16 complement to one of the longer chromosomes, with loss of the centromere of the small chromosome. The total chromosome lengths of the two types thus remained not significantly different, which is in line with the few small morphological differences which were detectable between the two types. Of considerably phylogenetic interest was the finding of complete inter-sterility of the two M. murex types. Neither M. aculeata 2n= 16 nor M. constricta 2n=14 could be crossed with M. murex of the same chromosome number. Inviable hybrids were obtained on crossing M. murex 2n= 16 with M. turbinata 2n=16. The spiny vs. spineless pod character was investigated in the 2n=16 type and found to be inherited on a monofactorial basis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293912
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  • 6
    Electronic Resource
    Electronic Resource
    The nature and extent of synaptonemal complex formation in haploid barley (1974)
    Springer
    Chromosoma 48 (1974), S. 441-453 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Normal synaptonemal complexes have been found in haploid barley meiotic prophase at stages equivalent to pachytene in diploids. Reconstructions of serially sectioned nuclei have shown that up to 60% of the haploid chromosomes may pair in either intra- or interchromosomal associations. The extent and nature of the synaptonemal complex formation suggest that the chromosome pairing is non-homologous. From the virtual absence of chiasmata in metaphase I stages of the haploids it is inferred that crossing over requires a more precise DNA alignment than is provided by synaptonemal complex formation alone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00290998
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  • 7
    Electronic Resource
    Electronic Resource
    An electron microscopic study of synaptonemal complex formation at zygotene in rye (1985)
    Springer
    Chromosoma 92 (1985), S. 165-175 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A spreading technique was used to allow ultrastructural analysis of seventeen zygotene nuclei of rye (Secale cereale). Twenty pachytene nuclei were also examined. Lateral element lengths of the haploid complements decreased from 742 μm at the beginning of zygotene to 451 μm at the end of zygotene. Variation in pachytene synaptonemal complex lengths was also noted. Zygotene synaptonemal complex formation in rye is characterised by: (1) existence of a bouquet, with telomeric pairing initiation earliest; (2) multiple sites of initiation in each bivalent (maximum of 76 synaptonemal complex segments seen in one nucleus); (3) the potential number of pairing initiation sites may be higher (the average spacing of 4.42 μm would allow approximately 160 sites per nucleus); (4) new pairing initiations occur almost until the end of zygotene; (5) initiation of new synaptonemal complexes and extension of existing synaptonemal complexes occur simultaneously. A simple zipping up of a few initiation sites is not the case in rye. Pairing in different bivalents of a nucleus is not completely synchronised, and the NOR in particular is often late to pair. Interlocking of lateral elements and synaptonemal complexes may lead to delayed completion of pairing in portions of bivalents, but interlocks are ultimately resolved. This resolution may involve breakage and rejoining of lateral elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348690
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  • 8
    Electronic Resource
    Electronic Resource
    The effect of Ph gene alleles on synaptonemal complex formation in Triticum aestivum × T. kotschyi hybrids (1987)
    Springer
    Theoretical and applied genetics 74 (1987), S. 430-438 
    Details
    ISSN: 1432-2242
    Keywords: Triticum hybrids ; Homoeologous pairing ; Ph gene ; ph mutant ; Synaptonemal complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Chromosome pairing at zygotene-pachytene was studied in Triticum aestivum × T. kotschyi hybrids (2n=5x=35, genomic constitution ABDCUSv) by electron microscopy of synaptonemal complexes in spread microsporocyte nuclei. Hybrids carrying either the Ph allele or the ph allele, which differ markedly in metaphase I pairing, are both capable of greater than 90% pachytene pairing, although pairing in the Ph hybrids appeared slower or less synchronised. In both genotypes branched synaptonemal complexes were formed by intra-and interchromosomal pairing. The Ph gene control on homoeologous pairing does not act on the ability to pair into synaptonemal complexes. It may act on the rate of pairing or the time of crossing over.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00289817
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  • 9
    Electronic Resource
    Electronic Resource
    Pachytene studies in 2n=14 species of Medicago (1971)
    Springer
    Genetica 42 (1971), S. 278-298 
    Details
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four annual species of Medicago (M. constricta Dur., M. polymorpha L., M. praccox D.C. and M. rigidula [L.] All.) were analysed at pachytene and idiograms prepared. Considerable differences in chromosome lengths and arm ratios occurred between species. In three of the species the longest chromosome of the complement was much longer than the second chromosome in the karyotype. In this respect they were similar to 2n=14 M. murex Willd., and similar types of origins by rranslocations from 2n=16 ancestors are probable. In M. constricta chromosome 1 was not exceptionally long, and different kinds of translocations may have been involved in its origin. The M. constricta idiogram was most like the M. rigidula idiogram, and the M. praecox idiogram was most like the M. polymorpha idiogram. These similarities support present taxonomic classification. However, the great similarity of the M. polymorpha idiogram to that previously deseribed for 2n=14 M. murex was unexpected, as these two species are usually classified in different subsections of the genus. A closer relationship is suggested. Evidence was found in M. polymorpha of variations in chromosome contraction and differences in karyotype between accessions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00123323
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  • 10
    Electronic Resource
    Electronic Resource
    The pachytene synaptonemal complex complement of the cat (1985)
    Springer
    Genetica 67 (1985), S. 99-107 
    Details
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Surface spreads of pachytene spermatocyte nuclei from two cats were used to construct a synaptonemal complex karyotype for the cat. It was possible to recognise the 18 autosomal synaptonemal complexes by reference to a published light microscopic banded somatic karyotype. Some variation from the somatic karyotype was noted, presumably as a result of differential contraction during prophase I. The X and Y chromosome axes were joined by a synaptonemal complex in many of the nuclei, but the structure of the unpaired portion of the X axis was quite variable. In some nuclei it was highly contracted, while in others it was extended and often was split into two or more axes. In most nuclei the autosomal synaptonemal complexes had numerous axial twists.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02424416
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