scholarly journals Two types of highly ordered micro- and macrochromosome arrangement in metaphase plates of butterflies (Lepidoptera)

2019 ◽  
Vol 13 (1) ◽  
pp. 19-25 ◽  
Author(s):  
Vladimir A. Lukhtanov
Keyword(s):  
Metaphase Plate ◽  
Meiotic Metaphase ◽  
Chromosome Organization ◽  
Cell Divisions ◽  
Size Groups ◽  
Metaphase I

In karyotype of many organisms, chromosomes form two distinct size groups: macrochromosomes and microchromosomes. During cell divisions, the position of the macro- and microchromosomes is often ordered within metaphase plate. In many reptiles, amphibians, birds, insects of the orthopteran family Tettigoniidae and in some plants, a so called “reptilian” type organization is found, with microchromosomes situated in the center of metaphase plate and with macrochromosomes situated at the periphery. An opposite, “lepidopteran” type is known in butterflies and moths (i.e. in the order Lepidoptera) and is characterized by macrochromosomes situated in the center and by microchromosomes situated at the periphery. The anomalous arrangement found in Lepidoptera was previously explained by holocentric organization of their chromosomes. Here I analyse the structure of meiotic metaphase I plates in ithomiine butterfly, Forbestraolivencia (H. Bates, 1862) (Nymphalidae, Danainae, Ithomiini) which has a clear “reptilian” organization, contrary to previous observations in Lepidoptera. In this species large bivalents (i.e. macrochromosomes) form a regular peripheral circle, whereas the minute bivalents (i.e. microchromosomes) occupy the center of this circle. The reasons and possible mechanisms resulting in two drastically different spatial chromosome organization in butterflies are discussed.

Chromosome organization in meiosis revealed by light microscope analysis of silver-stained cores

Genome ◽  
1987 ◽  
Vol 29 (5) ◽  
pp. 706-712 ◽  
Author(s):  
J. S. Rufas ◽  
J. Gimenez-Abian ◽  
J. A. Suja ◽  
C. Garcia De La Vega
Keyword(s):  
Key Words ◽  
Light Microscope ◽  
Meiotic Chromosome ◽  
Chiasma Formation ◽  
Silver Impregnation ◽  
Meiotic Metaphase ◽  
Chromosome Organization ◽  
Microscope Analysis ◽  
Impregnation Technique ◽  
Metaphase I

Three species of grasshoppers have been analyzed by means of a modified silver impregnation technique that reveals the presence of a chromatid core that identifies chiasmata at first meiotic metaphase. In terms of the behaviour of the chromatid core most of the configurations observed at diplotene with orcein are easily recognized in metaphase I silver-stained bivalents. Some "hidden" configurations, as well as simple chromatin associations, that do not appear to represent chiasmata have also been detected. The disposition and behaviour of the chromatid cores in metaphase I and anaphase I provide grounds to support a reorganization of half-bivalents between first and second division. Key words: chromatid core, meiotic chromosome organization, chiasma formation, insect cytogenetics.

Metaphase position of an interchange quadrivalent of Allium triquetrum

1988 ◽  
Vol 90 (3) ◽  
pp. 493-499
Author(s):  
GEOFFREY K. RICKARDS ◽  
WENDY A. BAKER
Keyword(s):  
Linear Array ◽  
Metaphase Plate ◽  
Real Data ◽  
Slide Preparation ◽  
Metaphase I

The position of an interchange quadrivalent at metaphase I of Allium triquetrum was modelled so as to simulate the original placement of the quadrivalent in the spindle and the preparation of linear spreads through squashing. In this way an expected distribution for the quadrivalent in linear spreads was generated. The procedure used polar views of metaphase I to which the quadrivalent was assigned pairs of positions normally occupied by bivalents. The positions of the bivalents and assigned quadrivalent were then into a linear array and analysed as ‘real’ data. Comparisons with observed distributions showed that a general bias in favour of marginal placement of the quadrivalent in the linear array is expected; and also showed that the quadrivalent is positioned non-randomly in the metaphase plate prior to slide preparation.

scholarly journals The equatorial position of the metaphase plate ensures symmetric cell divisions

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Chia Huei Tan ◽  
Ivana Gasic ◽  
Sabina P Huber-Reggi ◽  
Damian Dudka ◽  
Marin Barisic ◽  
...  
Keyword(s):  
Spindle Assembly Checkpoint ◽  
Metaphase Plate ◽  
Spindle Assembly ◽  
Equatorial Position ◽  
Asymmetric Cell Divisions ◽  
Daughter Cells ◽  
Cell Divisions ◽  
Microtubule Stability ◽  
Chromosome Alignment ◽  
Metazoan Cell

Chromosome alignment in the middle of the bipolar spindle is a hallmark of metazoan cell divisions. When we offset the metaphase plate position by creating an asymmetric centriole distribution on each pole, we find that metaphase plates relocate to the middle of the spindle before anaphase. The spindle assembly checkpoint enables this centering mechanism by providing cells enough time to correct metaphase plate position. The checkpoint responds to unstable kinetochore–microtubule attachments resulting from an imbalance in microtubule stability between the two half-spindles in cells with an asymmetric centriole distribution. Inactivation of the checkpoint prior to metaphase plate centering leads to asymmetric cell divisions and daughter cells of unequal size; in contrast, if the checkpoint is inactivated after the metaphase plate has centered its position, symmetric cell divisions ensue. This indicates that the equatorial position of the metaphase plate is essential for symmetric cell divisions.

THE ULTRASTRUCTURE OF KINETOCHORES OF UNPAIRED CHROMOSOMES IN A WHEAT HYBRID

1973 ◽  
Vol 15 (4) ◽  
pp. 801-806 ◽  
Author(s):  
E. B. Wagenaar ◽  
D. F. Bray
Keyword(s):  
Sister Chromatid ◽  
Metaphase Plate ◽  
Polar Regions ◽  
Equatorial Plate ◽  
Univalent Chromosome ◽  
Wheat Hybrid ◽  
Opposite Pole ◽  
Kinetochore Region ◽  
Metaphase I

The kinetochore region of unpaired chromosomes (univalents) consists of two kinetochores, each belonging to a sister chromatid, that are located adjacent to one another on the surface of the univalent chromosome. This condition results in a movement by the univalent towards one of the polar regions at the onset of metaphase I. Once arrived in this region, one of the sister kinetochores obtains attachments of microtubules from the opposite pole. This results in a gradual return of the univalent to the equatorial plate, where it reaches an equilibrium. The sister kinetochores remain adjacent during the movement, but once arrived at the metaphase plate they develop a typical mitotic appearance, in which the sister kinetochores have opposite positions on the chromosomes.

The three-dimensional arrangement of chromosomes at meiotic metaphase I in normal and interchange heterozygotes of Briza humilis

1990 ◽  
Vol 97 (3) ◽  
pp. 565-570
Author(s):  
JANET M. MOSS ◽  
BRIAN G. MURRAY
Keyword(s):  
Mother Cell ◽  
Three Dimensional ◽  
Meiotic Metaphase ◽  
Central Position ◽  
Normal Plant ◽  
Serial Sections ◽  
Pollen Mother Cells ◽  
Sector Analysis ◽  
Mother Cells ◽  
Metaphase I

Pollen mother cells at metaphase I have been reconstructed from serial sections in normal and interchange heterozygotes of Briza humilis. The pollen mother cells have an irregular shape with a prominent projection from the tangential face into the anther loculus. The seven bivalents of the normal plant are usually arranged with one bivalent in a central position surrounded by a ring of the remaining six or as a ring of all seven bivalents. The central:peripheral distribution of quadrivalents is different in two different interchange plants; in a sector analysis, where cells are divided into four quarters relative to the tangential face of the pollen mother cell, the two plants also show differences in quadrivalent distribution, indicating that individual chromosomes occupy different positions in the cell. The relevance of these results to the positioning of quadrivalents in lateral squashes of meiotic metaphase I are discussed.

The Effect of Trifluralin on the Ultrastructure of Dividing Cells of the Root Meristem of Cotton (Gossypium Hirsutum L. ‘ACALA 4-42’)

1974 ◽  
Vol 15 (2) ◽  
pp. 429-441
Author(s):  
D. HESS ◽  
D. BAYER
Keyword(s):  
Cell Division ◽  
Gossypium Hirsutum ◽  
Lateral Root ◽  
Root Meristem ◽  
Metaphase Plate ◽  
Threshold Concentration ◽  
Gossypium Hirsutum L ◽  
Ultrastructural Studies ◽  
Cell Divisions ◽  
Dividing Cells

Ultrastructural studies of trifluralin-treated cells in lateral root meristems of cotton (Gossypium hirsutum L.) revealed that mitotic disruptions were due to the absence of microtubules. The extent of disruption varied between individual roots and correlated with the presence or absence of microtubules. Where microtubules were absent, cells began division with a normal prophase chromosome cycle. The chromosomes did not line up along a metaphase plate, but coalesced in the cell. If cell division had begun prior to microtubule disappearance the mitotic process was arrested at the stage that had been reached when the disappearance occurred. In some cell divisions randomly oriented microtubules were noted, with mitosis apparently arrested at those stages. Nuclear envelope reformation yielded cells that were polyploid, polymorphonucleate, binucleate, or occasionally multinucleate. If microtubules were present and if their orientation were normal, all stages of mitosis occurred. The range of mitotic disruption observed can be explained by the threshold concentration for microtubule disappearance being very near aqueous saturation of trifluralin.

Incomplete pole orientation of kinetochores in complex meiotic metaphase I configurations delays metaphase–anaphase transition in Secale

Genome ◽  
2014 ◽  
Vol 57 (4) ◽  
pp. 233-238
Author(s):  
J. Sybenga
Keyword(s):  
Chromosome Segregation ◽  
Secale Cereale ◽  
Anther Development ◽  
Meiotic Metaphase ◽  
Mild Form ◽  
Reciprocal Translocations ◽  
Chromatid Cohesion ◽  
Pole Orientation ◽  
Metaphase I

To prevent unbalanced chromosome segregation, meiotic metaphase I – anaphase I transition is carefully regulated by delaying anaphase until all kinetochores are well oriented (anaphase checkpoint) in mammals and insects. In plants this has not yet been established. In heterozygotes of two reciprocal translocations of Secale cereale, with one chromosome replaced by its two telocentric arms, anaphase delay was correlated with the orientation of the kinetochores of the complex of five chromosomes. The terminal kinetochores of the half chromosomes were readily elongated and pole oriented. Chains of five chromosomes with all five kinetochores orienting on alternate poles where the first to start anaphase. Kinetochores of two adjacent chromosomes when oriented on the same pole were partly shielded and less well pole directed. Anaphase was delayed. Cells with this configuration accumulated during anther development. Kinetochores in metacentric chromosomes lacking chiasmata in one arm (in trivalents and bivalents) were slightly better pole oriented and delayed anaphase less. Release of chromatid cohesion as triggered by kinetochore stretch is apparently delayed by inadequate exposition and pole orientation of the kinetochores. It is a mild form of an anaphase checkpoint, in normal material synchronizing bivalent segregation.

Independent arrangement of bivalents and (or) quadrivalents in linear meiotic metaphase plates of rye

Genome ◽  
1991 ◽  
Vol 34 (3) ◽  
pp. 421-429 ◽  
Author(s):  
P. G. Goicoechea ◽  
A. Roca ◽  
A. R. Linde ◽  
T. Naranjo ◽  
R. Giraldez
Keyword(s):  
Meiotic Metaphase ◽  
Relative Positioning ◽  
C Banding ◽  
Ring Bivalents ◽  
Type 3 ◽  
Metaphase I

The relative positioning of bivalents and (or) quadrivalents in flattened lateral views of metaphase I (linear metaphase plates) has been analyzed in three different plant types of rye: normal plants (type 1); heterozygotes for translocation T305W (type 2); and double heterozygotes for translocations T305W and TR01 (type 3). In all plant types all bivalents and (or) quadrivalents were identified using C-banding. The results indicate that quadrivalents show a preference towards being located in marginal positions of the linear plate, and there are also differences in position preferences between specific bivalents. Adjacently oriented quadrivalents and rod bivalents show a stronger preference for marginal positions than alternate quadrivalents and ring bivalents, respectively, but this does not indicate the existence of a fixed or ordered arrangement of chromosomes in the spindle since bivalents and (or) quadrivalents are independently located relative to each other.Key words: Secale, meiosis, metaphase, arrangement, multivalents, bivalents.

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