Chiasma redistribution in the presence of different sized supernumerary segments in a grasshopper: dependence on nonhomologous synapsis

Genome ◽  
1997 ◽  
Vol 40 (5) ◽  
pp. 682-688 ◽  
Author(s):  
A. L. del Cerro ◽  
J. L. Santos
Keyword(s):  
Synaptonemal Complex ◽  
Synaptonemal Complexes ◽  
Chiasma Distribution ◽  
Length Measurements ◽  
Extra Segment ◽  
Synaptic Process ◽  
Nonhomologous Synapsis

Eight different sized supernumerary segments located at distal ends of the long arms of chromosomes M4, M5, M6, and S8 of the grasshopper Stenobothrus festivus were studied in males with regard to the synaptic process and chiasma distribution in the bivalents that carry them. The M4, M5, and M6 bivalents heterozygous for extra segments were always monochiasmate, in contrast to their bichiasmate condition observed in basic homozygotes. Furthermore, the presence of any of these extra segments led to chiasma redistribution in the carrier bivalents, so that such chiasmata were formed preferentially further away from the extra segment. The intensity of this effect is dependent on the size of the segment. Not all heteromorphic bivalents exhibited synaptonemal complexes with equalized axes at pachytene, but there was always a variable proportion of heterosynapsis around the distal ends of the long arms that was dependent on both the size of the segment and the size of the carrier chromosome. It is proposed that the absence of chiasmata in nonhomologous synapsed regions is responsible for the results obtained. Length measurements of the different extra segments and their carrier chromosomes between pachytene and diplotene indicated that synaptonemal complex is underrepresented in supernumerary heterochromatin.Key words: chiasma distribution, grasshopper, heterosynapsis, supernumerary segment, synaptonemal complex.

Recombination nodule mapping and chiasma distribution in spermatocytes of the pigeon, Columba livia

Genome ◽  
1999 ◽  
Vol 42 (2) ◽  
pp. 308-314 ◽  
Author(s):  
M I Pigozzi ◽  
A J Solari
Keyword(s):  
Synaptonemal Complex ◽  
Random Distribution ◽  
Phosphotungstic Acid ◽  
Columba Livia ◽  
Complex Karyotype ◽  
Synaptonemal Complexes ◽  
Recombination Nodules ◽  
Chiasma Distribution ◽  
The Mean ◽  
Good Agreement

Pigeon spermatocytes were processed with a drying-down technique and their synaptonemal complex (SC) complements were analyzed by electron microscopy. The synaptonemal complex karyotype of the macrobivalents shows an excellent correspondence with the mitotic karyotype. The number and distribution of recombination nodules (RNs) were scored in complete nuclei stained with phosphotungstic acid. The average number of RNs per nucleus is 64.7. The number of nodules per bivalent shows a clear linear relationship with SC length in the 10 longest synaptonemal complexes, while the microbivalents usually bear a single RN. The location of RNs has a non-random distribution along the largest synaptonemal complexes, with lower frequencies near kinetochores and higher frequencies toward the telomeres. The ZZ bivalent is the fourth in size and shows free recombination, having on average 3.8 RNs. The mean number of nodules per cell and the mean number of nodules in the largest bivalents show very good agreement with the corresponding number of chiasmata scored in metaphase-I spermatocytes. It is concluded that the recombination nodules provide a good check for reciprocal exchanges in this and other species of birds. Additionally, a new morphology for the recombination nodules is presented, consisting of groups of electron-dense particles measuring 43 nm in diameter.Key words: meiosis, chiasmata, recombination nodules, pigeon spermatogenesis.

The synaptonemal complexes of Achlya recurva (Oomycetes): karyotype analysis and three-dimensional reconstruction of pachytene nuclei in antheridia and oogonia

1991 ◽  
Vol 69 (6) ◽  
pp. 1384-1395 ◽  
Author(s):  
Hobart R. Williamson ◽  
Pesach Ben Yitzchak
Keyword(s):  
Synaptonemal Complex ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolus Organizer Region ◽  
Three Dimensional ◽  
Central Element ◽  
Three Dimensional Reconstruction ◽  
Synaptonemal Complexes ◽  
Sequence Of Events ◽  
Dimensional Reconstruction

Fifteen synaptonemal complexes, as determined by three-dimensional reconstruction of serial, ultrathin sections, were present within both antheridial and oogonial zygotene and pachytene nuclei of the oomyceteous fungus Achlya recurva, thus n = 15. The present study represents the first complete reconstruction of synaptonemal complexes in the genus Achlya. The occurrence of both zygonema and pachynema was simultaneous in antheridia and oogonia. Pachytene nuclei of antheridia and oogonia are small, 13 μm3 in volume, and the average length of the synaptonemal complexes ranged from 1.9 to 4.4 μm. Lateral elements at zygotene ranged from 1.2 to 4.7 μm. Both ends of each synaptonemal complex were attached randomly to the nuclear envelope, so a bouquet formation was not observed at pachytene. In A. recurva, the dimensions of the synaptonemal complex were as follows: overall width = 270 nm; the lateral elements = 75 nm each in width and the central region = 120 nm. There was no central element and associated transverse filaments, which may be associated with development of alternative reproductive strategies other than amphimixis, as in nematodes. Of the 15 synaptonemal complexes present, only the one carrying the nucleolus organizer region could be clearly identified from one nucleus to the next. The nucleolar organizer region was on the average 0.75 μm from the telomere in both zygotene and pachytene nuclei. There were an average of three recombination nodules in each nucleus. Synaptonemal complexes have been reported in over 80 different species of fungi and related protista. Karyotypic evolution in the oomycetes and fungi may be the result of poly-ploidization, followed by cytogenetic diversification involving aneuploidy and differing degrees of polyploidy. Such a sequence of events could explain the apparent polyphyletic formation of this group. Key words: karyotype, Oomycetes, pachytene, synaptonemal complexes, three-dimensional reconstruction.

Synapsis in grasshopper bivalents heterozygous for centric shifts

Genome ◽  
1995 ◽  
Vol 38 (3) ◽  
pp. 616-622 ◽  
Author(s):  
A. L. del Cerro ◽  
J. L. Santos
Keyword(s):  
Chiasma Formation ◽  
The Other ◽  
Homologous Chromosomes ◽  
Synaptonemal Complexes ◽  
Chiasma Distribution ◽  
Centric Shift ◽  
Heterochromatin Polymorphism ◽  
Pachytene Spermatocytes ◽  
Surface Spread ◽  
Surface Spreading

Analysis of surface-spread synaptonemal complexes of zygotene and pachytene spermatocytes was carried out on centric-shift heterozygotes of grasshoppers. These rearrangements affected the M7 chromosome in Chorthippus vagans and the M6 and S8 chromosomes in Chorthippus apricarius. The shifts in the latter two chromosomes were also associated with C-heterochromatin variations between homologous chromosomes. Rearranged chromosomes proceeded directly to heterosynapsis without an apparent intervening homosynaptic phase in M7 bivalents of Ch. vagans and M6 bivalents of Ch. apricarius. In the latter case, axial equalization of the heterochromatin polymorphism was also achieved. On the other hand, asynapsis of the intercentromeric regions throughout pachytene was the rule in the centric shift involving the S8 chromosome of Ch. apricarius. In the three cases analysed, the production of unbalanced gametes in the heterozygotes is precluded either by the lack of chiasma formation in heterosynapsed rearranged segments or by the lack of pairing between such segments. Chiasmata were limited to the homologous regions of the heteromorphic bivalents.Key words: synapsis, surface spreading, centric shift, chiasma distribution, meiosis.

scholarly journals Meiotic cohesin REC8 marks the axial elements of rat synaptonemal complexes before cohesins SMC1β and SMC3

2003 ◽  
Vol 160 (5) ◽  
pp. 657-670 ◽  
Author(s):  
Maureen Eijpe ◽  
Hildo Offenberg ◽  
Rolf Jessberger ◽  
Ekaterina Revenkova ◽  
Christa Heyting
Keyword(s):  
Synaptonemal Complex ◽  
Sister Chromatid ◽  
Meiotic Prophase ◽  
S Phase ◽  
Synaptonemal Complexes ◽  
Sister Chromatids ◽  
Chromatid Cohesion ◽  
Axial Element ◽  
Striking Contrast ◽  
Metaphase I

In meiotic prophase, the sister chromatids of each chromosome develop a common axial element (AE) that is integrated into the synaptonemal complex (SC). We analyzed the incorporation of sister chromatid cohesion proteins (cohesins) and other AE components into AEs. Meiotic cohesin REC8 appeared shortly before premeiotic S phase in the nucleus and formed AE-like structures (REC8-AEs) from premeiotic S phase on. Subsequently, meiotic cohesin SMC1β, cohesin SMC3, and AE proteins SCP2 and SCP3 formed dots along REC8-AEs, which extended and fused until they lined REC8-AEs along their length. In metaphase I, SMC1β, SMC3, SCP2, and SCP3 disappeared from the chromosome arms and accumulated around the centromeres, where they stayed until anaphase II. In striking contrast, REC8 persisted along the chromosome arms until anaphase I and near the centromeres until anaphase II. We propose that REC8 provides a basis for AE formation and that the first steps in AE assembly do not require SMC1β, SMC3, SCP2, and SCP3. Furthermore, SMC1β, SMC3, SCP2, and SCP3 cannot provide arm cohesion during metaphase I. We propose that REC8 then provides cohesion. RAD51 and/or DMC1 coimmunoprecipitates with REC8, suggesting that REC8 may also provide a basis for assembly of recombination complexes.

G-band position effects on meiotic synapsis and crossing over.

Genetics ◽  
1988 ◽  
Vol 118 (2) ◽  
pp. 307-317
Author(s):  
T Ashley
Keyword(s):  
Complex Formation ◽  
Synaptonemal Complex ◽  
Chromosomal Rearrangement ◽  
Chromosomal Rearrangements ◽  
Crossing Over ◽  
Position Effects ◽  
Band Position ◽  
Synaptonemal Complex Formation ◽  
Meiotic Synapsis ◽  
Nonhomologous Synapsis

Abstract An examination of synaptic data from a series of X-autosome translocations and crossover data from an extensive series of autosome-autosome translocations and autosomal inversions in mice has lead to the development of a hypothesis which predicts synaptic and recombinational behavior of chromosomal aberrations during meiosis. This hypothesis predicts that in heterozygotes for chromosomal rearrangements that meiotically align G-light chromatin with G-light chromatin lack of homology will be recognized. If homologous synapsis cannot proceed, synaptonemal complex formation will cease and there will be no physical suppression of crossing over in such rearrangements. However, if a chromosomal rearrangement aligns G-light chromatin with G-dark chromatin at the time of synapsis, lack of homology will not be recognized and synaptonemal complex formation will proceed nonhomologously through the G-dark chromatin. Crossing over will be physically suppressed in this region and this suppression of crossing over will be confined to the chromosome in which the G-light chromatin is nonhomologously synapsed with G-dark chromatin. When G-light chromatin is once again aligned with G-light chromatin, lack of homology again will be recognized and either homologous synapsis will be reinitiated (as in an inversion loop), or will cease altogether (as in some translocations). Unlike the previously described "synaptic adjustment", this nonhomologous synapsis of G-light with G-dark chromatin appears to compete with homologous synapsis during early pachynema.

Indiscriminate synapsis in achiasmate Allium fistulosum L. (Liliaceae)

1992 ◽  
Vol 103 (2) ◽  
pp. 415-422
Author(s):  
G. Jenkins ◽  
A. Okumus
Keyword(s):  
Synaptonemal Complex ◽  
Allium Fistulosum ◽  
Cell Nuclei ◽  
Male Sterile ◽  
Allium Species ◽  
Lateral Element ◽  
Synaptonemal Complexes ◽  
Independent Process ◽  
Surface Spread ◽  
Metaphase I

Seedlings of Allium fistulosum (2n=2x=16) were treated with aqueous colchicine with the intention of inducing tetraploidy. One treated, but undoubled, diploid mutant is described which consistently fails to form any chiasmata at diakinesis and metaphase I of meiosis. Electron microscopy of whole-mount surface-spread synaptonemal complex complements of pollen mother cell nuclei revealed that the achiasmate condition is probably due not only to the failure to complete synapsis, but also to the indiscriminate way in which the chromosomes form synaptonemal complexes during meiotic prophase. Synapsis begins and progresses with complete disregard to homology, with frequent exchanges of pairing partners resulting in the formation of multiple associations comprising heterologous chromosomes. Intrachromosomal synapsis is also evident as fold-back loops. Up to 78% of lateral element length is incorporated into synaptonemal complex, the morphology of which is not unlike that of normal A. fistulosum and other Allium species described previously. However, all the synaptonemal complexes are ineffective in terms of supporting chiasmata, since 16 univalents enter metaphase I and disjoin irregularly at anaphase I. The mutant is as a consequence completely male sterile. The synaptic behaviour observed confirms that the recognition of homology is an independent process and not a prerequisite for synaptonemal complex formation. It is hoped this mutant will be a valuable tool for probing the molecular basis of homology.

Meiosis in triploid Lolium. I. Synaptonemal complex formation and chromosome configurations at metaphase I in aneuploid autotriploid L. multiflorum

Genome ◽  
1994 ◽  
Vol 37 (2) ◽  
pp. 181-189 ◽  
Author(s):  
Huw M. Thomas ◽  
Barry J. Thomas
Keyword(s):  
Complex Formation ◽  
Synaptonemal Complex ◽  
Lolium Multiflorum ◽  
Synaptonemal Complexes ◽  
Pollen Mother Cells ◽  
Partner Exchange ◽  
Synaptonemal Complex Formation ◽  
Mother Cells ◽  
Axial Element ◽  
Metaphase I

A spreading technique for synaptonemal complexes (SCs) was applied to pollen mother cells of two aneuploid genotypes of autotriploid Lolium multiflorum (2n = 3x + 1 = 22). In the earliest nuclei analyzed the axial elements are in six groups of 3 and one group of 4. Most groups have formed multivalents with from one to five pairing partner exchanges, but there are also groups that have formed bivalents and univalents. Some axial elements have formed triple associations, in one case for the length of the trivalent. Unsynapsed axial elements remain aligned with their homologous SCs into pachytene, but this alignment is abolished as these axes pair heterologously among themselves until the entire axial element complement is synapsed. At metaphase I most chromosomes are associated as trivalents and quadrivalents.Key words: Lolium, triploid, pairing partner exchange, chiasma, multivalent.

A TECHNIQUE FOR LIGHT AND ELECTRON MICROSCOPY OF THE SYNAPTONEMAL COMPLEX OF THE MOUSE OOCYTE

1982 ◽  
Vol 24 (6) ◽  
pp. 675-680 ◽  
Author(s):  
Weng Kong Sung ◽  
Georgiana Jagiello
Keyword(s):  
Electron Microscopy ◽  
Synaptonemal Complex ◽  
Microscopic Examination ◽  
Light And Electron Microscopy ◽  
Electron Microscopic Examination ◽  
Mouse Oocyte ◽  
Electron Microscopic ◽  
Synaptonemal Complexes

A method is described for obtaining synaptonemal complex preparations from mouse pachytene oocytes for light and electron microscopic examination. A karyotype based on the whole complement of synaptonemal complexes of a pachytene oocyte as visualized by electron microscopy is presented.

Dependence on genie balance for synaptonemal complex formation in Drosophila melanogaster

Genome ◽  
1988 ◽  
Vol 30 (2) ◽  
pp. 258-264 ◽  
Author(s):  
T. M. Grishayeva ◽  
Y. F. Bogdanov
Keyword(s):  
Drosophila Melanogaster ◽  
Synaptonemal Complex ◽  
X Chromosome ◽  
Central Element ◽  
Sharp Decrease ◽  
Electron Microscopic Examination ◽  
Electron Microscopic ◽  
X Chromosomes ◽  
Ovary Cells ◽  
Synaptonemal Complexes

Electron microscopic examination of gonads of Drosophila melanogaster with different genotypes, including a metafemale 3X;2A and an intersex XXY;3A, have revealed that the formation of synaptonemal complexes is controlled by the genie balance, i.e., the ratio of X chromosomes to autosomes. The Y chromosome is not involved in the genetic control of the formation of precursors of the central element of synaptonemal complexes in males, nor does it disturb their formation in [Formula: see text] females. Hyperploidy for sections 1 – 3A and 18A – 20 of the X chromosome does not lead to the appearance of synaptonemal complexes in males and does not interfere with their formation in females. Females hyperploid for extensive regions of the X chromosome (sections 1 – 11A, 11A – 20, and 8C – 20) are fertile and show apparently normal formation of synaptonemal complexes. Hyperploidy for sections 8C – 11A of the X results in a sharp decrease in the viability of females, in abnormal differentiation of ovary cells, and in the lack of synaptonemal complexes. These data suggest a possible important role for the sections 8C – 11A in the genic balance controlling the formation of synaptonemal complexes in D. melanogaster. The lack of synaptonemal complexes in hypoploid females may be the result of abnormal cell differentiation in gonads.Key words: Drosophila melanogaster, synaptonemal complex, sex chromosomes, genic balance.

Presence of abnormal synaptonemal complexes in heterothallic species of Neurospora

Genome ◽  
1988 ◽  
Vol 30 (5) ◽  
pp. 697-709 ◽  
Author(s):  
Maja Bojko
Keyword(s):  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Low Frequency ◽  
Chiasma Formation ◽  
Lateral Component ◽  
Late Pachytene ◽  
Synaptonemal Complexes ◽  
Neurospora Intermedia ◽  
Heterothallic Species ◽  
Type Strains

Synaptonemal complex abnormalities are frequent in reconstructed meiotic prophase nuclei of Neurospora crassa and Neurospora intermedia. Three kinds of synaptonemal complex anomalies were seen: lateral component splits, lateral component junctions, and multiple complexes. The anomalies apparently are formed during or after the pairing process, as they were not seen in the largely unpaired early zygotene chromosomes. Their presence at all the other substages from mid-zygotene to late pachytene indicates that they are not eliminated before the synaptonemal complex decomposes at diplotene. Abnormal synaptonemal complexes were seen in all 19 crosses of N. crassa and N. intermedia that were examined, including matings between standard laboratory strains, inversions, Spore killers, and strains collected from nature. The frequency of affected nuclei and degree of abnormality within a nucleus varied in different matings. No abnormalities were present in the homothallic species Neurospora africana and Neurospora terricola. Structural chromosome aberrations, introgression, and heterozygosity have been eliminated as causes for pairing disorder. The abnormal synaptonemal complexes seemingly do not interfere with normal ascus development and ascospore formation. The affected nuclei are not aborted during meiotic prophase, nor are they eliminated by abortion of mature asci. The abnormal meiocytes do not lead to aneuploidy, as judged by the low frequency of white ascospores in crosses between wild type strains that have many abnormalities. Thus, the abnormal synatonemal complexes do not appear to prevent chiasma formation between homologues.Key words: Neurospora, meiosis, synaptonemal complex.

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