scholarly journals A possible effect of B-chromosomes on metaphase I homologous chromosome association in rye

Heredity ◽  
1991 ◽  
Vol 67 (1) ◽  
pp. 123-128 ◽  
Author(s):  
M T Alvarez ◽  
A Fominaya ◽  
M Perez de la Vega
Keyword(s):  
Homologous Chromosome ◽  
B Chromosomes ◽  
Chromosome Association ◽  
Metaphase I

Cytogenetics of decaploid Agropyron elongatum (Elytrigia elongata) (2n = 70). I. Frequency of decavalent formation

Genome ◽  
1990 ◽  
Vol 33 (6) ◽  
pp. 811-817 ◽  
Author(s):  
Mikio Muramatsu
Keyword(s):  
High Frequency ◽  
Chromosome Association ◽  
Agropyron Elongatum ◽  
Homologous Chromosomes ◽  
Ring Shape ◽  
Meiotic Configuration ◽  
Multivalent Formation ◽  
A Cell ◽  
Chromosome Associations ◽  
Metaphase I

The multivalents that appeared in the decaploid strain of Agropyron elongatum (2n = 10x = 70), a relative of wheat, ranged from trivalent to decavalent. Few univalents occurred. The metaphase I chromosome association in 12 cells where all configurations could clearly be identified averaged 0.42 ring X + 0.17 chain X + 0.42 ring VIII + 0.17 branched VIII + 0.25 chain VIII + 0.17 chain VII + 1.17 ring VI + 0.33 branched VI + 0.5 chain VI + 1.67 ring IV + 0.42 branched IV + 0.58 chain IV + 0.08 branched III + 0.17 chain III + 12.58 ring II + 3.75 open II + 0.25 I. The occurrence of decavalents, up to two in one cell, and of a cell with five multivalents, each of which involved more than five chromosomes, and many multivalents of ring shape indicated that the strain is autodecaploid.The chromosome associations of each cell can be interpreted as seven groups of 10 homologous chromosomes. The high frequency of bivalents indicated a tendency toward reduced multivalent formation, for which an explanation is suggested.Key words: Agropyron elongatum, meiotic configuration, decaploid, multivalent.

scholarly journals Meiotic and mitotic behaviour of B chromosomes of ryegrass

2009 ◽  
Vol 40 (1) ◽  
pp. 83-88 ◽  
Author(s):  
Vânia Helena Techio ◽  
Andréa Mittelmann ◽  
Simone Marció ◽  
Antônio Vander Pereira
Keyword(s):  
Rio Grande ◽  
B Chromosomes ◽  
Rio Grande Do Sul ◽  
Anther Tapetum ◽  
Root Meristems ◽  
Fluorescent Stains ◽  
Meiotic Analyses ◽  
Metaphase I

Mitotic and meiotic analyses using conventional and fluorescent stains were employed in plants (accession ETBAZ 055 - origin: Capão do Leão, Rio Grande do Sul State, Brazil) from the Germplasm Active Bank of Ryegrass (Banco Ativo de Germoplasma de Azevém) of Embrapa, for observing the behaviour of B chromosomes. In several meiotic stages, there were observed up to two B chromosomes, which have presented an unstable behaviour regarding their precocious ascension to metaphase I or delays during anaphase I. At the end of the process, the Bs showed predominantly segregation for the nuclei under formation in order to guarantee their propagation. Concerning the cells that comprise the anther tapetum and the root meristems, the B chromosomes have presented a more stable behaviour.

scholarly journals Cytogenetics ofOryctes nasicornisL. (Coleoptera: Scarabaeidae: Dynastinae) with Emphasis on Its Neochromosomes and Asynapsis Inducing Premature Bivalent and Chromosome Splits at Meiosis

2012 ◽  
Vol 2012 ◽  
pp. 1-6
Author(s):  
B. Dutrillaux ◽  
A. M. Dutrillaux
Keyword(s):  
B Chromosomes ◽  
Meiotic Behaviour ◽  
Normal Appearance ◽  
Unusual Behaviour ◽  
Meiotic Chromosomes ◽  
Autosome Translocation ◽  
Variable Character ◽  
Metaphase I

The chromosomes of specimens ofOryctes nasicornisfrom three locations in France and two locations in Greece were studied. All karyotypes have an X-Y-autosome translocation: 18, neoXY. Two male specimens from France (subspeciesnasicornis) displayed an unusual behaviour of their meiotic chromosomes in 30–50% of spermatocytes, with asynapsis at pachynema, premature bivalent and chromosome split at metaphases I and II. The karyotypes remained balanced at metaphase I, but not at metaphase II. These particularities mimic the meiotic behaviour of B chromosomes and question about their existence, reported earlier in Spanish specimens. Due to the variable character of B chromosomes, complementary analyses are needed. To our knowledge, such meiotic particularities have not been described, beside cases of infertility. In specimens from Corsica (subspecieslaevigatus) and Greece (subspecieskuntzeni), all spermatocytes I and II had a normal appearance. The meiotic particularity may thus be limited to male specimens from subspeciesnasicornis.

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.

Comparative chromosome pairing in triploids and diploids of perennial Triticeae

Genome ◽  
1990 ◽  
Vol 33 (1) ◽  
pp. 89-94 ◽  
Author(s):  
Richard R.-C. Wang
Keyword(s):  
Chromosome Pairing ◽  
Chromosome Association ◽  
Hordeum Bulbosum ◽  
Perennial Species ◽  
Chromosome Homology ◽  
Basic Genome ◽  
Genome Homology ◽  
First Time ◽  
Tribe Triticeae ◽  
Metaphase I

Meiotic data were obtained for the triploid hybrids Pseudoroegneria libanotica (2n = 14; SS) × P. stipifolia (2n = 28; SSSS), P. spicata (2n = 28; SSSS) × P. spicata (2n = 14; SS), P. strigosa (2n = 28; SSSS) × P. stipifolia (2n = 14; SS) for the first time. Additional polyhaploid plants of Critesion iranicum (2n = 42; HvHvHvHvHvHv) and triploid Hordeum bulbosum (HbHbHb) were also analyzed at metaphase I. The relationships between chromosome association at metaphase I in the autotriploids and in the corresponding diploids of perennial species in the tribe Triticeae were analyzed. The results corroborated the findings in an earlier study that the trivalent frequency in triploids having one or two basic genome(s) is positively correlated with the degree of genome homology in their corresponding diploids. Therefore, chromosome association at metaphase I in diploids is a function of chromosome homology and is a legitimate tool for studying genome relationships.Key words: genome, meiosis, autoploid, alloploid, homology, homoeology.

Comparison between synaptonemal complexes at pachytene and chromosome association at metaphase I in heterozygotes for a "nonreciprocal" translocation of rye

Genome ◽  
1989 ◽  
Vol 32 (6) ◽  
pp. 983-991 ◽  
Author(s):  
T. Naranjo ◽  
A. Roca ◽  
P. G. Goicoechea ◽  
J. H. de Jong ◽  
W. D. Smilde
Keyword(s):  
Complex Formation ◽  
Synaptonemal Complex ◽  
Secale Cereale ◽  
Chiasma Formation ◽  
Chromosome Association ◽  
Simultaneous Occurrence ◽  
Negative Interference ◽  
Secale Cereale L ◽  
Synaptonemal Complex Formation ◽  
Metaphase I

A comparative analysis of synaptonemal complex formation at pachytene and chromosome association at metaphase I was carried out in heterozygotes for translocation T242W (2R/6R) of rye (Secale cereale L.). Synaptonemal complex formation supported earlier light microscopic observations that one exchanged segment of this translocation was very small and restricted to the telomere or had been lost. Negative interference between the interstitial segments with respect to chiasma formation was detected at metaphase I. This interference was apparently the result of the simultaneous occurrence of either asynapsis or nonhomologous pairing around the translocation point at pachytene. Negative interference detected across the centromere of 6R was attributed to nonhomologous pairing. The presence of an intercalary C-band in the interstitial segment 2RLi or in the 1RS arm had no apparent influence on synaptonemal complex formation. Unmatched ends of synaptonemal complex 1R and of the multivalent were in most cases associated with heterozygosity for the telomeric C-heterochromatin.Key words: Secale cereale, translocation, synapsis, interference, C-banding.

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