Unpaired sex chromosomes in metaphase I human spermatocytes locally modify autosomal bivalents positioning

Meiosis in males of the F5 cytotype of Sceloporus grammicus was examined through the analysis of synaptonemal complexes (SCs), diakinetic (metaphase I) nuclei, and secondary spermatocytes (metaphase II configurations). These data allowed the establishment of criteria for substaging of zygonema and pachynema, morphological characterization of the SC complement, and comparison of the orientation and segregation of the autosomes and sex chromosomes. The analysis of nuclei from all stages of meiotic prophase I (leptonema through diakinesis) provided a useful means of partitioning the temporal sequence of early meiotic events. Three substages of zygonema (Z1–Z3) were established, based on the extent of synapsis of the microchromosomal and macrochromosomal elements. Synaptic initiation of the autosomes and sex chromosomes was synchronous. Two patterns of macrochromosomal synapsis were observed. Whereas synapsis of the biarmed elements was biterminal (i.e., progressing from both ends of the homologs), synapsis of the acrocentric elements was uniterminal involving only the distal (noncentromeric) ends of the homologs. Unique sex-chromosomal characteristics were not observed in S. grammicus and, therefore, the substaging of pachynema was based on subjective criteria. Examination of diakinesis – metaphase I and metaphase II configurations indicated low levels of diakinetic irregularities with balanced segregation of the autosomal bivalents and the sex-chromosomal trivalent.Key words: Sceloporus grammicus, meiosis, synaptonemal complex, substaging.

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Sex chromosome configurations in pachytene spermatocytes of an XYY mouse

Genetics Research ◽

10.1017/s0016672300035205 ◽

1990 ◽

Vol 56 (2-3) ◽

pp. 129-133 ◽

Cited By ~ 2

Author(s):

Charles Tease

Keyword(s):

Sex Chromosomes ◽

Male Mouse ◽

Sex Chromosome ◽

Chromosome Constitution ◽

Sterile Male ◽

Xy Bivalent ◽

Pachytene Spermatocytes ◽

Metaphase I

SummaryKaryotypic investigation of a phenotypically normal but sterile male mouse showed the presence of an XYY sex chromosome constitution. The synaptic behaviour of the three sex chromosomes was examined in 65 pachytene cells. The sex chromosomes formed a variety of synaptic configurations: an XYY trivalent (40%); an XY bivalent and Y univalent (38·5%); an X univalent and YY bivalent (13·8%); or X, Y, Y univalence (7·7%). There was considerable variation in the extent of synapsis and some of the associations clearly involved nonhomologous pairing. These observations have been compared with previously published information on chromosome configurations at metaphase I from other XYY males.

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Undifferentiated sex chromosomes in Mastotermes darwiniensis Froggatt (Isoptera; Mastotermitidae) and the evolution of eusociality in termites

Genome ◽

10.1139/g87-013 ◽

1987 ◽

Vol 29 (1) ◽

pp. 76-79 ◽

Cited By ~ 7

Author(s):

D. G. Bedo

Keyword(s):

Key Words ◽

Sex Chromosomes ◽

Sex Chromosome ◽

Mitotic Metaphase ◽

Evolution Of Sex ◽

Termite Species ◽

Chromosome Differentiation ◽

Evolution Of Eusociality ◽

Metaphase I

Meiosis and mitosis was studied in males of the primitive termite Mastotermes darwiniensis, which is closely related to the Dictyoptera. In mitotic metaphase cells 98 chromosomes were found with a matching 49 bivalents at metaphase I. Mastotermes darwiniensis has a largely acrocentric karyotype with no sex-linked translocation complexes, like those found in many other termite species, or other sex chromosome differentiation. These observations suggest that ancestral termites probably had karyotypes with many small chromosomes lacking sex chromosome differentiation and that there is no connection between the evolution of sex-linked translocation complexes and eusociality. Key words: sex chromosomes, Mastotermes, termites, eusociality.

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Localized recombination nodules and sex chromosome behavior in the male mole cricket, Neocurtilla hexadactyla

Genome ◽

10.1139/g89-440 ◽

1989 ◽

Vol 32 (2) ◽

pp. 275-281 ◽

Cited By ~ 2

Author(s):

B. Spyropoulos ◽

D. Wise ◽

P. B. Moens

Keyword(s):

Synaptonemal Complex ◽

Sex Chromosomes ◽

Sex Chromosome ◽

Chromosome X ◽

Chromosome Behavior ◽

Autosomal Bivalents ◽

Electron Dense Material ◽

Recombination Nodules ◽

The Third ◽

Mole Cricket

During meiotic prophase, the 10 metacentric autosomal bivalents of the mole cricket, Neocurtilla hexadactyla Perty, formed synaptonemal complexes only at their ends. These complexes were of similar morphology to those of other species. Virtually all of these distal synaptonemal complex segments contained one or more recombination nodules. There was complete correlation between the locations of the synaptonemal complex segments at pachytene and chiasmata at diplotene. The sex chromosomal bivalent X2 and Y, formed a synaptonemal complex at one end only. While no apparent physical or spatial connection was found during prophase between the X2Y bivalent and the third sex chromosome, X1, electron-dense material covered the centromeres of X1 and Y and to a lesser extent X2, thus differentiating the centromeres of the sex chromosomes from those of the autosomes.Key words: localised pairing, recombination nodules, chiasmata, sex chromosomes.

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Meiotic chromosome structure. Kinetochores and chromatid cores in standard and B chromosomes of Arcyptera fusca (Orthoptera) revealed by silver staining

Genome ◽

10.1139/g91-004 ◽

1991 ◽

Vol 34 (1) ◽

pp. 19-27 ◽

Cited By ~ 13

Author(s):

J. A. Suja ◽

J. de la Torre ◽

J. F. Giménez-Abián ◽

C. García de la Vega ◽

J. S. Rufas

Keyword(s):

Meiotic Division ◽

Silver Staining ◽

Chromosome Structure ◽

Sex Chromosome ◽

Meiotic Chromosome ◽

B Chromosomes ◽

Chromosome Organization ◽

Autosomal Bivalents ◽

Metaphase I

The behaviour of two chromosome structures in silver-stained chromosomes was analyzed through the first meiotic division in spermatocytes of the acridoid species Arcyptera fusca. Results showed that at diakinesis kinetochores and chromatid cores are individualized while they associate in bivalents of metaphase I; only kinetochores and distal core spots associate in the sex chromosome. Metaphase I is characterized by morphological and localization changes of both kinetochores and cores which define the onset of anaphase I. These changes analyzed in both autosomes and in the sex chromosome allow us to distinguish among three different substages in metaphase I spermatocytes. B chromosomes may be present as univalents, bivalents, or trivalents. Metaphase I B univalents are characterized by separated cores except at their distal ends and individualized and flat sister kinetochores. At anaphase I sister kinetochores of lagging B chromatids remain connected through a silver-stained strand. The behaviour of cores and kinetochores of B bivalents is identical with that found in the autosomal bivalents. The differences in the morphology of kinetochores of every chromosome shown by B trivalents at metaphase I may be related to the balanced forces acting on the multivalent. The results show dramatic changes in chromosome organization of bivalents during metaphase I. These changes suggest that chromatid cores are not involved in the maintenance of bivalents. Moreover, the changes in morphology of kinetochores are independent of the stage of meiosis but correlate with the kind of division (amphitelic–syntelic) that chromosomes undergo.Key words: kinetochore, chromatid core, B chromosomes, meiosis, chromosome structure, silver staining.

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Cytogenetics of chromosome rearrangements in Tribolium castaneum

Genome ◽

10.1139/g95-085 ◽

1995 ◽

Vol 38 (4) ◽

pp. 673-680 ◽

Cited By ~ 11

Author(s):

Jeffrey J. Stuart ◽

Giovani Mocelin

Keyword(s):

Tribolium Castaneum ◽

Relative Length ◽

Red Flour Beetle ◽

Linkage Groups ◽

Mitotic Chromosomes ◽

Autosomal Bivalents ◽

Flour Beetle ◽

Spermatogonial Metaphase ◽

Restriction Enzyme Banding ◽

Metaphase I

The karyotype of the red flour beetle, Tribolium castaneum, was reexamined and improved by restriction enzyme banding with HpaII. After this treatment, each of the 10 chromosomes were identified in spermatogonial metaphase cells and 3 of the 8 autosomal bivalents and the XY pair were identified in spermatocyte metaphase I nuclei. Based on centromere position, relative length, and banding pattern, probable correlations between some of the mitotic chromosomes and some of the metaphase I bivalents were ascertained. Thus improved, the karyotypes of beetles harboring genetically defined translocations were investigated. Spermatocyte metaphase I nuclei were most informative, as normal chromosome pairing was visibly disrupted by rearrangements. Bivalents associated with each rearrangement were identified. Results demonstrated that each of the five best defined T. castaneum linkage groups corresponds to a different chromosome and established correspondence between bivalents and linkage groups 1–4. The relevance of these findings is discussed with regard to Tribolium genetics and evolution.Key words: beetles, red flour beetle, Coleoptera, linkage groups, chromosome banding.

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The pattern of sex chromosome kinetochore phosphorylation during nonrandom segregation in a flea beetle

Biochemistry and Cell Biology ◽

10.1139/o00-002 ◽

2000 ◽

Vol 78 (2) ◽

pp. 93-98

Author(s):

Holly Kupfer ◽

Dwayne Wise

Keyword(s):

Key Words ◽

Sex Chromosomes ◽

Sex Chromosome ◽

Flea Beetle ◽

Beetle Species ◽

Kinetochore Protein ◽

Linear Configuration ◽

Meiosis I ◽

Metaphase I

In the flea beetle species, Alagoasa bicolor, males have two sex chromosomes, X and Y, each of which is larger than the rest of the genome combined. These large sex chromosomes do not pair at meiosis I, and are therefore not joined at metaphase I. Nevertheless, they always segregate from each other at anaphase I. As prometaphase I progresses, the unpaired X and Y undergo reorientation from a parallel to a linear configuration. Using 3F3/2, an antibody that detects the level of phosphorylation of a kinetochore protein or proteins, we have determined that this reorientation is not accompanied by a change in the level of phosphorylation of the kinetochores of either X or Y. This implies that: i) either the reorientation does not involve the loss or gain of kinetochore microtubules, or ii) if such loss or gain occurs, it does not effect a change in the tension placed on the nonrandomly segregating kinetochores, or iii) the sex chromosomes, as in some other species, have lost the ability to sense kinetochore tension changes. Evolution of nonrandom segregation may necessitate the inability of the participating chromosomes to affect the metaphase checkpoint. Key words: nonrandom segregation, sex chromosomes, kinetochores.

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Evolution of the Sex Chromosomes in Beetles. I. The Loss of the Y Chromosome

Cytogenetic and Genome Research ◽

10.1159/000478075 ◽

2017 ◽

Vol 152 (2) ◽

pp. 97-104 ◽

Cited By ~ 4

Author(s):

Anne-Marie Dutrillaux ◽

Bernard Dutrillaux

Keyword(s):

Y Chromosome ◽

Sex Chromosomes ◽

Silver Staining ◽

Sex Chromosome ◽

B Chromosomes ◽

Chromosome Constitution ◽

Chromosome Loss ◽

Autosomal Bivalents ◽

C Banding ◽

Nucleolar Proteins

In the males of Coleoptera, the most frequent sex chromosome constitution is XY. At metaphase I of meiosis, the X and Y are linked by nucleolar proteins, forming the so-called parachute bivalent (Xyp), which is assumed to allow the non-synapsed X and Y to segregate correctly at anaphase I. However, X0 males are not exceptional, and we explored the relationships between the X and nucleolar proteins in the absence of the Y chromosome in 6 species belonging to different families/subfamilies. Using C-banding and silver staining, we show that nucleolar proteins always remain in contact with the X until anaphase I. These proteins are generally more abundant than in the Xyp bivalent, may remain associated with the NOR during diakinesis, and frequently link the X to 1 or 2 autosomal bivalents, which seem to play the same role as the Y. This role may also be played by B chromosomes, which appear to be more frequent in X0 than in XY males. In conclusion, following Y chromosome loss, various strategies using nucleolar proteins have been developed to facilitate the migration of the unique X at meiotic anaphase I.

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Fine structure and behaviour of a pericentric inversion in the sand rat, Psammomys obesus

Journal of Cell Science ◽

10.1242/jcs.50.1.105 ◽

1981 ◽

Vol 50 (1) ◽

pp. 105-119

Author(s):

T. Ashley ◽

M.J. Moses ◽

A.J. Solari

Keyword(s):

Sex Chromosomes ◽

Pericentric Inversion ◽

Psammomys Obesus ◽

Homologous Pairing ◽

Sand Rat ◽

Autosomal Bivalents ◽

Late Pachytene ◽

Early Pachytene ◽

Break Points ◽

Pachytene Spermatocytes

In pachytene spermatocytes of the sand rat, Psammomys obesus, a long autosomal bivalent was observed, which was asynaptic for a large interstitial segment of its length in early pachytene. This bivalent also exhibited unaligned kinetochores. In late pachytene spermatocytes all autosomal bivalents were fully synapsed, but one of the shortest bivalents now possessed unaligned kinetochores. Evidence is presented in support of the proposition that the asynaptic interstitial region observed in early pachytene is due to the bivalent being heterozygous for a pericentric inversion. Using the maximum extent of homologous pairing, the break points were mapped at 26% from one end and 20% from the other. The unaligned kinetochores support the proposal that the aberration is an inversion and measurements of their positions confirm the estimated break points. In one cell a bivalent with interstitial (but no terminal) synapsis also confirms the inversion hypothesis. It is proposed that the bivalent is so small that topological considerations prevent the formation of the expected inversion loop. Evidence is also presented that complete synapsis of the bivalent during late pachytene can be attributed so ‘synaptic adjustment’, characterized by non-homologous synapsis (heterosynapsis). The position of the aberrant bivalent in relation to the sex chromosomes also changes during pachytene. When the bivalent is incompletely synapsed it generally associates by its ends with the ends of the sex chromosomes, but when it is non-changes during pachytene. When the bivalent is incompletely synapsed it generally associates by its ends with the ends of the sex chromosomes, but when it is non-homologously synapsed it is not associated with them.

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Studies on the karyotype and gametogenesis in Trichuris muris

Journal of Helminthology ◽

10.1017/s0022149x0001350x ◽

1994 ◽

Vol 68 (1) ◽

pp. 67-72 ◽

Cited By ~ 7

Author(s):

M. Špakulová ◽

I. Králová ◽

C. Cutillas

Keyword(s):

Sex Chromosomes ◽

Diploid Number ◽

Cytological Study ◽

Trichuris Muris ◽

Classical Pattern ◽

Males And Females ◽

Metaphase I

AbstractThe cytological study of males and females of Trichuris muris (Schrank, 1788) revealed the diploid number of chromosomes to be 2n=6. The sex determining mechanism was XX♀/XY♂. All the chromosomes were subtelocentric. Sex chromosomes formed the smallest pair, but X and Y were difficult to distinguish morphologically. Chromosome changes during gametogenesis in both sexes followed a classical pattern except in the male prophase and metaphase I. Four male autosomes formed two bivalents, each with one proximal chiasma with strict localization, while sex chromosomes X and Y formed two univalents. Female chromosomes formed three rod bivalents type, which possessed three, two and two chiasmata.

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