Heterochromatin distribution and chiasma localization in the grasshopper Bryodema tuberculata (fabr.) (Acrididae)

Chromosoma ◽  
1974 ◽  
Vol 44 (4) ◽  
pp. 393-404 ◽  
Author(s):  
I. Klášterská ◽  
A. T. Natarajan ◽  
C. Ramel
Keyword(s):  
Chiasma Localization

The Form of Bivalent Chromosomes in Newt Oocytes at First Metaphase of Meiosis

1963 ◽  
Vol s3-104 (66) ◽  
pp. 281-295
Author(s):  
I. D. WATSON ◽  
H. G. CALLAN
Keyword(s):  
Genetic Recombination ◽  
Great Majority ◽  
Meiotic Metaphase ◽  
Gene Products ◽  
Lampbrush Chromosomes ◽  
Female Sex ◽  
Chiasma Localization

Lampbrush chromosomes in the ovarian oocytes of newts are associated as bivalents. Some connexions between lampbrush chromosomes are chiasmata; others are known to be fusions of gene products; yet others, namely reflected, centromere, and telomere fusions, do not appear to be due simply to the fusion of gene products. Whether chiasmata are involved in reflected, centromere, and telomere fusions cannot be decided from examination of the chromosomes at the lampbrush stage. Bivalents from oocytes at first meiotic metaphase were therefore studied. The oocytes of newts reach first meiotic metaphase after ovulation, whilst they are free in the coelome. Reflected, centromere, and the great majority of telomere fusions do not persist to first meiotic metaphase: thus chiasmata are not involved in them. In oocyte bivalents of Triturus helveticus chiasmata are not restricted in their distribution, whereas in spermatocyte bivalents of this species chiasmata are proterminally localized. In oocyte bivalents of 3 subspecies of T. cristatus chiasmata are procentrically localized, whereas in spermatocyte bivalents of these subspecies chiasmata are not restricted in their distribution. Thus in T. helveticus meiosis in the female sex is mainly responsible for genetic recombination, whereas in T. cristatus the situation is reversed. We conclude that to base genetical and evolutionary inferences on information drawn from the meiosis of one sex only is unjustified, and we doubt the validity of the claim that chiasma localization has arisen so as to restrict genetic recombination.

Influence of heterochromatin on chiasma localization and terminalization in maize

Caryologia ◽  
1995 ◽  
Vol 48 (3-4) ◽  
pp. 247-253 ◽  
Author(s):  
Rosana Torrezan ◽  
Maria Suely Pagliarini
Keyword(s):  
Chiasma Localization

Cytology of the tetraploidAllium ampeloprasum with chiasma localization

Chromosoma ◽  
1970 ◽  
Vol 29 (1) ◽  
pp. 12-19 ◽  
Author(s):  
A. K. Koul ◽  
R. N. Gohil
Keyword(s):  
Chiasma Localization

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.

Chiasma localization, heterochromatin and synaptonemal complexes in the grasshopperPyrgomorpha conica

1996 ◽  
Vol 4 (1) ◽  
pp. 69-76 ◽  
Author(s):  
A. L. del Cerro ◽  
A. Fernández ◽  
J. L. Santos
Keyword(s):  
Synaptonemal Complexes ◽  
Chiasma Localization
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