The effect of B-chromosomes on chiasma frequency in wild populations of rye

Chromosoma ◽  
1969 ◽  
Vol 27 (2) ◽  
pp. 198-200 ◽  
Author(s):  
Lj. Zečević ◽  
Dobrila Paunović
Keyword(s):  
Chiasma Frequency ◽  
B Chromosomes ◽  
Wild Populations

THE EFFECTS OF SUPERNUMERARY CHROMATIN IN THREE SPECIES OF GRASSHOPPER

1974 ◽  
Vol 16 (2) ◽  
pp. 285-296 ◽  
Author(s):  
Gilbert L. Schroeter ◽  
Godfrey M. Hewitt
Keyword(s):  
Life Cycle ◽  
Chiasma Frequency ◽  
Genetic Material ◽  
B Chromosomes ◽  
Population Variability ◽  
The Other ◽  
Direct Effects ◽  
Apparent Effect ◽  
Other Hand ◽  
The Mean

The chiasma frequencies in males of three species of grasshopper with and without B-chromosomes and supernumerary segments were scored at diplotene. The partially heterochromatic B's found in some individuals of Chimarocephala pacifica pacifica have no effect on chiasma frequencies. On the other hand, heterochromatic supernumerary segments in Oedaleonotus phryneicus males significantly increase the mean chiasma frequencies over individuals without them but not the between-cell variances. In Camnula pellucida neither the mitotically unstable B's nor supernumerary segments have any apparent effect on chiasma.frequencies. The supernumerary elements in Chimarocephala pacifica and Camnula pellucida may, however, produce other effects during the life cycle These and previous observations suggest that polymorphism involving extra genetic material in grasshoppers can result in increased population variability via two different means: (1) by producing variation in chiasma frequency or (2) through direct effects in the individuals possessing it. The importance of such a mechanism for producing variation is discussed.

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.

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.

The B chromosomes of Locusta migratoria. II. Effects on chiasma frequency

Genome ◽  
1988 ◽  
Vol 30 (2) ◽  
pp. 118-123 ◽  
Author(s):  
Esther Viseras ◽  
F. Javier Salcedo ◽  
Juan Pedro M. Camacho
Keyword(s):  
Environmental Factors ◽  
Genetic Relationship ◽  
Chiasma Frequency ◽  
Locusta Migratoria ◽  
B Chromosomes ◽  
A Cell ◽  
Genetic And Environmental Factors ◽  
Close Genetic Relationship ◽  
Accessory Chromosomes

The effects of accessory chromosomes of Locusta migratoria have been tested at intra- and inter-individual levels. Intraindividual analysis demonstrated that chiasma frequency of a cell is independent of the number of B-chromosomes that it contains. Interindividual analysis was done using males with a close genetic relationship (brother–brother and father–son) as well as males not showing such relationship. This analysis demonstrated the importance of both genetic and environmental factors in determining chiasma frequency. It was concluded that B chromosomes have no influence on this character.Key words: Locusta, B chromosomes, chiasma frequency.

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.

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