Cytological aspects of gametogenesis in two rhigonematid (Nematoda) parasites of Anadenobolus politus (Porat) (Rhinocricidae; Diplopoda) from Guadeloupe

1984 ◽  
Vol 62 (2) ◽  
pp. 190-192 ◽  
Author(s):  
Martin L. Adamson ◽  
Daniel Van Waerebeke
Keyword(s):  
X Chromosome ◽  
Meiotic Prophase ◽  
Meiotic Metaphase ◽  
Autosomal Pair

Certain cytological aspects of gametogenesis are examined in two species of rhigonematid nematodes parasitizing the posterior gut of Anadenobolus politus (Rhinocricidae; Diplopoda) in Guadeloupe. In both species, sex is determined by an XX/XO mechanism; this is taken as an indication of the phylogenetic distinctness of rhigonematids from the order Oxyurida which recent studies show to be haplodiploid. In Ichthyocephalus anadenoboli. males had 9 and females had 10 chromosomes; in Heth mauriesi, males had 15 and females had 16 chromosomes. In both species, the X chromosome and one autosomal pair were positively heteropyenotic (i.e., they condensed before and stained more intensely than the rest of the chromosomes) during meiotic prophase in males; in H. mauriesi, these chromosomes were negatively heteropyenotic during meiotic metaphase in males. In females of both species, all chromosomes stained similarly.

scholarly journals X chromosome activity in female germ cells of mice heterozygous for Searle's translocation T(X;16)16H

1981 ◽  
Vol 37 (3) ◽  
pp. 317-322 ◽  
Author(s):  
P. G. Johnston
Keyword(s):  
X Chromosome ◽  
Germ Cells ◽  
Meiotic Prophase ◽  
Somatic Cells ◽  
Phosphoglycerate Kinase ◽  
Inactive X Chromosome ◽  
Faint Band

SUMMARYThe expression of X-linked phosphoglycerate kinase (PGK-1) in germ cells from embryos heterozygous for both PGK-1 and Searle's translocation T(X; 16) 16H was examined to investigate X chromosome activity during oogenesis. The Pgk-lb allele on the translocated X chromosome was the only allele active in somatic cells of all embryos and in germ cells from 12·5 d.p.c. embryos. However, an additional faint band representing Pgk-la activity was observed in germ cells from older embryos (13·5–18·5 d.p.c.) and neonates (1–2 d.p.p.). It is concluded that there is a period when only one X chromosome is active in early female germ cells and that reactivation of the inactive X chromosome takes place just prior to meiotic prophase.

scholarly journals Pairing and synapsis in oocytes from female fetuses with euploid and aneuploid chromosome complements

Reproduction ◽  
2007 ◽  
Vol 133 (5) ◽  
pp. 899-907 ◽  
Author(s):  
P Robles ◽  
I Roig ◽  
R Garcia ◽  
A Ortega ◽  
J Egozcue ◽  
...  
Keyword(s):  
X Chromosome ◽  
Meiotic Prophase ◽  
High Efficiency ◽  
Extra Chromosome ◽  
Chromosome 21 ◽  
Pachytene Stage ◽  
Meiotic Process ◽  
Human Oocytes ◽  
Meiotic Progression ◽  
Aneuploid Chromosome

Only little is known about the meiotic prophase events in human oocytes, although some of them are involved in the origin of aneuploidies. Here, a broad study of the pairing and synaptic processes in 3263 human euploid and 2613 aneuploid oocytes (47,XX, +21 and 47,XX, +13), using different techniques and methods, is presented in order to elucidate the characteristics of this essential meiotic process. Our results reaffirm the existence of a common high efficiency in the pairing process leading to the obtainment of a bivalent for all chromosomes studied in euploid and aneuploid cases. Nevertheless, this high efficiency was insufficient to consistently produce trivalents in aneuploid oocytes. Trivalent 21 was only observed in 48.8% of the 47,XX, +21 pachytene-stage oocytes studied, and trivalent 13 was found in 68.7% of the 47,XX, +13 pachytene-stage oocytes analyzed. Our data confirm the hypothesis which suggests that in human oocytes the presence of an extra chromosome could interfere in bouquet dynamics. In addition, the pairing process of the X chromosome is altered in trisomic 21 oocytes, providing evidence of the influence that an extra chromosome 21 may cause meiotic progression.

Reverse heteropyknosis between euchromatin and heterochromatin of the X chromosome in meiotic prophase of the cockroach Blaberus discoidalis

1983 ◽  
Vol 25 (1) ◽  
pp. 72-75
Author(s):  
Liming Shi ◽  
T. C. Hsu ◽  
Sen Pathak
Keyword(s):  
X Chromosome ◽  
Meiotic Prophase ◽  
Constitutive Heterochromatin ◽  
Staining Pattern ◽  
Hoechst 33258 ◽  
Blaberus Discoidalis ◽  
Bright Fluorescence ◽  
Karyological Evolution ◽  
As If

The X chromosome and all autosomes of the cockroach Blaberus discoidalis (2n = 37, XO) contain large segments of constitutive heterochromatin (C-bands). From spermatogonial metaphases, the C-bands are found to be located in the middle of most chromosomes, including the X. The C-bands show bright fluorescence when stained with Hoechst 33258. In pachytene, autosomal heterochromatin can be easily identified in acetic orcein squash preparations as condensed segments. In the same preparations the X chromosome exhibits a "closed" appearance with a lightly stained middle loop and two heavily stained terminal segments which lie side-by-side as if they are paired. In C-banded preparations, an opposite reaction is found, i.e., the loop is heavily stained while the tips are lightly stained. In Hoechst 33258 preparations, the loop is brightly fluorescent while the tips are less brightly stained. Thus, in pachytene of conventional orcein preparations the heteropyknotic behavior between euchromatin and heterochromatin of the X chromosome is the reverse of the usual staining pattern; instead of condensed heterochromatin and decondensed euchromatin, euchromatin is condensed whereas heterochromatin is decondensed. The "paired" euchromatic tips may suggest autologous homology between the original X and the original Y which might have been translocated onto the X in the course of karyological evolution.

scholarly journals DNA Environment of Centromeres and Non-homologous Chromosomes Interactions in Mouse

2021 ◽  
Author(s):  
Victor Spangenberg ◽  
Losev Michail ◽  
Volkhin Ilya ◽  
Svetlana Smirnova ◽  
Nikitin Pavel ◽  
...  
Keyword(s):  
Y Chromosome ◽  
X Chromosome ◽  
Satellite Dna ◽  
Meiotic Prophase ◽  
Centromeric Region ◽  
Autosomal Bivalents ◽  
Homologous Chromosomes ◽  
Prophase I ◽  
Meiotic Prophase I ◽  
Minor Satellite

Pericentromeric regions of chromosomes enriched in tandemly repeated satellite DNA although representing a significant part of eukaryotic genomes are still understudied mainly due to interdisciplinary knowledge gaps. Recent studies suggest their important role in genome regulation, karyotype stability and evolution. Thus, the idea of satellite DNA as a junk part of the genome was refuted. Integration of data about molecular composition, chromosome behaviour and details of in situ organization of pericentromeric regions is of great interest. The objective of this work was a cytogenetic analysis of the interactions of pericentromeric regions non-homologous chromosomes in mouse spermatocytes using immuno-FISH. We analysed two events: the associations between cerntomeric regions of X chromosome and autosomes, and associations between centromeric regions of autosomal bivalents forming chromocenters. We conclude that X chromosome form temporary synaptic associations with different autosomes in early meiotic prophase I which normally can be found at pachytene-diplotene without signs of pachytene arrest. These associations are formed between the satellite DNA-enriched centomeric regions of X chromosome and different autosomes but not involve the satellite-poor centromeric region of Y-chromosome. We suggest the mechanism of X chromosome competitive replacement from such associations during synaptic correction. We showed that centromeric region of the X chromosome remains free of γH2Ax-dependent chromatin inactivation, while Y chromosome is completely inactivated. This findings highlights the predominant role of associations between satellite DNA-enriched regions of different chromosomes including X. We assume that X-autosome temporary associations is a manifestation of an additional synaptic disorders checkpoint. These associations are normally corrected before the late diplotene. We revealed that the intense spreading conditions applied to the spermatocytes I nuclei did not lead to destruction of stretched chromatin fibers i.e. elongated chromocenters enriched in satellite DNA. Revealed by us tight associations between pericentromeric regions of different autosomal bivalents and X chromosome may represent the basis for repeat stability maintenance in autosomes an X chromosome. The consequences of our findings are discussed. We obtained the preparations of mouse spermatocytes nuclei in the meiotic prophase I using two approaches: standard and extremely intense surface spread techniques. Using immuno-FISH we visualized tandemly repeated mouse Major and Minor satellite DNA located in the pericentromeric regions of chromosomes and performed a morphological comparison of the standard- and intensely spreaded meiotic nuclei. Based on our results, we assume the remarkable strength of the chromocenter-mediated associations, “chromatin “bridges”, between different bivalents at the pachytene and diplotene stages. We have demonstrated that the chromocenter “bridges” between the centromeric ends of meiotic bivalents are enriched in both tandemly repeated Major and Minor satellite DNA. Association of centromeric regions of autosomal bivalents and X-chromosome but not with Y-chromosome correlates with the absence of Major and Minor satellites on Y-chromosome. We suggest that revealed tight associations between pericentromeric regions of bivalents may represent the network-like system providing dynamic stability of chromosomal territories, as well as add new data for the hypothesis of ectopic recombination in these regions which supports sequence homogeneity between non-homologous chromosomes and does not contradict the meiotic restrictions imposed by the crossing-over interference near centromeres. We conclude that nuclear architecture in meio-sis may play an essential role in contacts between the non-homologous chromosomes providing the specific characteristics of pericentromeric DNA.

Synaptonemal complex karyotyping in Melanoplus differentialis

1977 ◽  
Vol 26 (1) ◽  
pp. 229-250
Author(s):  
A.J. Solari ◽  
S.J. Counce
Keyword(s):  
Nuclear Envelope ◽  
X Chromosome ◽  
Meiotic Prophase ◽  
Polar Region ◽  
Relative Length ◽  
Characteristic Sequence ◽  
Mitotic Chromosomes ◽  
Nuclear Interior ◽  
Melanoplus Differentialis ◽  
The Relationship

The chromosomal axes of the spermatocytes of the grasshopper Melanoplus differentialis have been studied with a modification of the microspreading procedure used previously. The whole complement of synaptonemal complexes (SCs) and the axis of the X chromosome have been described and measured. The relative length of each SC is characteristic and constant and permits the construction of an idiogram. Relative lengths of SCs are almost equal to the relative lengths of mitotic chromosomes of spermatogonia (with the exception of the X chromosome), thus extending to an invertebrate the relationship between SCs and mitotic chromosomes that has been demonstrated in mammals. All the SCs except the 3 smallest (which are apparently telocentric) show a small short arm beyond the kinetochore. The progression of changes in the chromosomal axes during meiotic prophase has been staged by centriolar behaviour. During leptotene, axes are first formed near the nuclear envelope at a special (polar) region. SCs also begin to appear in the polar region and extend towards the nuclear interior. The beginning and completion of synapsis is not synchronous among bivalents. The X-axis is formed in midzygotene and shows a characteristic sequence of changes in shape during pachytene. Cells in post-synaptic stages show whole chromosome complements with characteristic chiasmatic configurations. Kinetochores are prominent and bipartite during diplotene-diakinesis.

scholarly journals Differential timing of S phases, X chromosome replication, and meiotic prophase in the C. elegans germ line

2007 ◽  
Vol 308 (1) ◽  
pp. 206-221 ◽  
Author(s):  
Aimee Jaramillo-Lambert ◽  
Marina Ellefson ◽  
Anne M. Villeneuve ◽  
JoAnne Engebrecht
Keyword(s):  
X Chromosome ◽  
Meiotic Prophase ◽  
Germ Line ◽  
Chromosome Replication ◽  
C Elegans ◽  
Differential Timing
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