Factors affecting the meiotic pairing behaviour of B chromosomes in the grasshopper Eyprepocnemis plorans

1984 ◽  
Vol 26 (6) ◽  
pp. 664-668 ◽  
Author(s):  
N. Henriques-Gil ◽  
P. Arana ◽  
J. L. Santos
Keyword(s):  
Chiasma Frequency ◽  
Chiasma Formation ◽  
B Chromosome ◽  
B Chromosomes ◽  
Meiotic Pairing ◽  
Eyprepocnemis Plorans ◽  
Factors Affecting ◽  
Chiasma Localization ◽  
A Site ◽  
Pairing Behaviour

A study of the meiotic behaviour of different B-chromosome variants in the acridid grasshopper Eyprepocnemis plorans demonstrates that pairing and chiasma formation in these supernumerary chromosomes depend both on genotypic factors and on the structure of the B chromosomes themselves. Genotypic effects are evidenced by the differences in chiasma frequency which the same B-chromosome combinations show in different individuals. Structural effects can be inferred from the fact that 9 of the 14 known known B variants carry a unique site to which interstitial chiasmata are confined, whereas such a site is lacking in the other five variants.Key words: B chromosomes, C-bands, chiasma frequency, chiasma localization.

Locating a site on the maize B chromosome that controls preferential fertilization

Genome ◽  
2007 ◽  
Vol 50 (6) ◽  
pp. 578-587 ◽  
Author(s):  
Wayne R. Carlson
Keyword(s):  
B Chromosome ◽  
B Chromosomes ◽  
Chromosome 9 ◽  
Chromosome Deletion ◽  
Pollen Mitosis ◽  
Preferential Fertilization ◽  
Second Pollen Mitosis ◽  
A Site ◽  
Derivatives Of

In maize, the B chromosome can undergo nondisjunction at the second pollen mitosis, producing sperm with two B chromosomes and sperm with zero B chromosomes. Preferential fertilization is the ability of the sperm carrying two B chromosomes to transmit more frequently to the embryo of a kernel than the sperm lacking the B chromosome. A translocation involving the B chromosome and chromosome 9, TB-9Sb, has been used to study preferential fertilization. The B-9 chromosome has the same properties of nondisjunction and preferential fertilization as the standard B chromosome. Deletion derivatives of B-9, which lack the centric heterochromatin and possibly some adjacent euchromatin, were tested for their ability to induce preferential fertilization. They were found to lack the capacity for preferential fertilization.

Ultrastructure of meiotic pairing in B chromosomes of Crepis capillaris. I. One-B and two-B pollen mother cells

Genome ◽  
1989 ◽  
Vol 32 (4) ◽  
pp. 611-621 ◽  
Author(s):  
G. H. Jones ◽  
J. A. F. Whitehorn ◽  
S. M. Albini
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Complex Surface ◽  
B Chromosome ◽  
B Chromosomes ◽  
Meiotic Pairing ◽  
Pollen Mother Cells ◽  
Crepis Capillaris ◽  
Axis Length ◽  
Mother Cells

Chromosome pairing of a small metacentric B chromosome in Crepis capillaris has been studied by synaptonemal complex surface spreading of pollen mother cells containing either one or two B chromosomes. The B-chromosome axis, on average, represents about 8.7% of the axis length of the standard A-chromosome set, which is less than the corresponding values for DNA content (10.6%) and mitotic chromosome volume (13.6%). Single B chromosomes commonly undergo fold-back pairing to give a symmetrical hairpin loop, which supports earlier suggestions that this B chromosome is an isochromosome. Two B chromosomes may show interarm pairing, exclusively, or interchromosome pairing, exclusively, or combinations of the two. Near the centromeres pairing occurs preferentially between arms of the same chromosome, but chromosome ends show random association. Some B chromosomes show anomalous pairing configurations, which may reflect further orders of reverse repeats within arms or, alternatively, nonhomologous pairing. The period of B-chromosome pairing is confined almost exclusively to zygotene, when the standard A chromosomes are pairing, but within this period their pairing is delayed relative to the A set. Individual B chromosomes at zygotene contain from one to three separate synaptonemal complex segments. These are widely distributed within the chromosomes, mainly in distal and interstitial regions; pairing is delayed around the centromere.Key words: B chromosomes, isochromosomes, synaptonemal complex.

scholarly journals Population Cytology of the Genus Phaulacridium VI. Seasonal Changes in the Frequency of the B Chromosome in a Population of Ph. vittatum

1977 ◽  
Vol 30 (4) ◽  
pp. 329 ◽  
Author(s):  
M Westerman ◽  
J Dempsey
Keyword(s):  
Seasonal Changes ◽  
Chiasma Frequency ◽  
Sequential Sampling ◽  
Late Summer ◽  
B Chromosome ◽  
B Chromosomes ◽  
Adult Males ◽  
University Campus ◽  
Maximum Value ◽  
Significant Difference

Sequential sampling of adult males from the La Trobe University campus population of Ph. Vittatum has been carried out over two successive years. Within each year there is seen to be a similar change in frequency of males carrying a large, mitotically stable B chromosome. Early in the summer, when adults first appear, the B frequency of the population is low; it then rises to a maximum value in late summer and then declines once more. Possible reasons for this change in B frequency are discussed. Chiasma frequency scores of individuals with and without B chromosomes were also recorded for each sample. It was found that although at anyone time there was no significant difference between individuals with and without B chromosomes, due no doubt to the small numbers sampled, nonetheless the chiasma frequency of the former was always higher than the latter. Since this was the finding for collections over three years, it is concluded that the B chromosomes of Ph. vittatum, like those of other acridids, raise mean cell chiasma frequency.

Relationship between pachytene synapsis, metaphase I associations, and transmission of 2B and 4B chromosomes in rye

Genome ◽  
2000 ◽  
Vol 43 (2) ◽  
pp. 232-239 ◽  
Author(s):  
Guillermo Jiménez ◽  
Silvia Manzanero ◽  
María J Puertas
Keyword(s):  
Secale Cereale ◽  
Maternal Effect ◽  
Chiasma Frequency ◽  
Transmission Rate ◽  
Chiasma Formation ◽  
B Chromosomes ◽  
Bivalent Formation ◽  
The Relationship ◽  
Variable Efficiency ◽  
Metaphase I

2B rye plants selected for high (H) or low (L) B transmission rate were studied at pachytene and metaphase I of meiosis to determine the relationship between synapsis, bivalents at metaphase I, and B transmission rate. The results show that the 2 B chromosomes (Bs) form bivalents at pachytene in both the H and L lines, whereas the frequency of bivalents at metaphase I is much higher in the H than in the L line. This demonstrates that B transmission is mainly related to the proper association of Bs at metaphase I, as well as that synapsis of the 2 Bs in the L line is normal, but the bivalent is not consolidated by a chiasma in most cases. Crosses were made between 2B plants of the H and L lines in all combinations (H × H, H × L, L × H, and L × L) to obtain 4B plants. Similarly, bivalent formation at pachytene and metaphase I was studied. The results show that 4B plants of the H × H and L × L classes differ significantly at pachytene and metaphase I since the former forms more bivalents. The heterozygous 4 Bs of the H × L and L × H classes show intermediate values. The relation H × H > H × L > L × H > L × L was consistently found for the variables transmission rate, bivalents at pachytene, bivalents at metaphase I, and B mean chiasma frequency. A maternal effect was also found. Our data suggest that there are two separate mechanisms acting upon synapsis and chiasma formation in H and L B chromosomes: (i) there is variable efficiency of the control of synapsis at early stages of meiosis; and (ii) there is variable efficiency of the control of the number of chiasmata. Key words: B chromosomes, synaptonemal complex, Secale cereale.

THE EFFECT OF ACCESSORY CHROMATIN ON CHIASMA DISTRIBUTION IN MAIZE

1976 ◽  
Vol 18 (3) ◽  
pp. 479-484 ◽  
Author(s):  
Edward J. Ward
Keyword(s):  
Zea Mays ◽  
Chiasma Frequency ◽  
Zea Mays L ◽  
Chiasma Formation ◽  
B Chromosome ◽  
Abnormal Chromosome ◽  
Chromosome 10 ◽  
Chiasma Distribution ◽  
Metaphase I

From an analysis of metaphase I bivalent configurations in Zea mays L. it was possible to determine the effects of two supernumerary elements on chiasma formation. Both the B chromosome and abnormal chromosome 10 increased chiasma frequency. In addition to enhancing total exchanges, both elements caused a redistribution of chiasmata from distal to more proximal locations.

B chromosomes of the grasshopper Heteracris littoralis: meiotic behaviour and endophenotypic effects in both sexes

Genome ◽  
1988 ◽  
Vol 30 (5) ◽  
pp. 797-801 ◽  
Author(s):  
M. I. Cano ◽  
J. L. Santos
Keyword(s):  
Chiasma Frequency ◽  
Main Type ◽  
Natural Populations ◽  
Meiotic Drive ◽  
B Chromosome ◽  
B Chromosomes ◽  
Female Meiosis ◽  
Accumulation Mechanism ◽  
Cell Variance ◽  
High Level

A main type of a large supernumerary B chromosome has been found in several natural populations of the grasshopper Heteracris littoralis. A study on the geographical distribution of the polymorphism and the meiotic behavior of Bs in both sexes has been carried out with special reference to their effect on two endophenotypic parameters: recombination level and macrospermatid production. Male B bivalents are characterized by a high level of pairing and a strict proximal localization of chiasmata. In the females the B chromosome always divides reductionally at anaphase I indicating the possible existence of an accumulation mechanism based on meiotic drive. There is no effect of Bs on either mean chiasma frequency or between-cell variance in either of the sexes. However, in males a positive correlation between the number of Bs and production of abnormal spermatids (macrospermatids) was found.Key words: B chromosomes, chiasma frequency, female meiosis.

scholarly journals B Chromosomes in Grasshoppers: Different Origins and Pathways to the Modern Bs

Genes ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 509 ◽  
Author(s):  
Ilyas Jetybayev ◽  
Alexander Bugrov ◽  
Victoria Dzuybenko ◽  
Nikolay Rubtsov
Keyword(s):  
Repetitive Sequences ◽  
B Chromosome ◽  
B Chromosomes ◽  
Eyprepocnemis Plorans ◽  
Grasshopper Species ◽  
Chromosome Formation ◽  
Different Origins ◽  
Further Development ◽  
New Hypothesis ◽  
Orthopteran Species

B chromosomes (Bs) were described in most taxa of eukaryotes and in around 11.9% of studied Orthopteran species. In some grasshopper species, their evolution has led to many B chromosome morphotypes. We studied the Bs in nine species (Nocaracris tardus, Nocaracris cyanipes, Aeropus sibiricus, Chorthippus jacobsoni, Chorthippus apricarius, Bryodema gebleri, Asiotmethis heptapotamicus songoricus, Podisma sapporensis, and Eyprepocnemis plorans), analyzing their possible origin and further development. The studied Bs consisted of C-positive or C-positive and C-negative regions. Analyzing new data and considering current hypotheses, we suggest that Bs in grasshoppers could arise through different mechanisms and from different chromosomes of the main set. We gave our special attention to the Bs with C-negative regions and suggest a new hypothesis of B chromosome formation from large or medium autosomes. This hypothesis includes dissemination of repetitive sequences and development of intercalary heterochromatic blocks in euchromatic chromosome arm followed by deletion of euchromatic regions located between them. The hypothesis is based on the findings of the Eyprepocnemis plorans specimens with autosome containing numerous intercalary repeat clusters, analysis of C-positive Bs in Eyprepocnemis plorans and Podisma sapporensis containing intercalary and terminal C-negative regions, and development of heterochromatic neo-Y chromosome in some Pamphagidae grasshoppers.

CHIASMA FORMATION IN THE SUB-METACENTRIC B-CHROMOSOME OF XANTHISMA TEXANUM DC.

1973 ◽  
Vol 15 (4) ◽  
pp. 871-873 ◽  
Author(s):  
John C. Semple
Keyword(s):  
Gene Mutations ◽  
Chiasma Formation ◽  
B Chromosome ◽  
B Chromosomes ◽  
Common Phenomenon

The B-chromosome of Xanthisma texanum is submetacentric, rather than telocentric as previously reported. Chiasma formation is a common phenomenon in both A-set chromosome bivalents and in B-chromosome bivalents. Theoretically recombination is possible and therefore evolution of B-chromosomes is not restricted to gene mutations alone.

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