Analysis of metaphase I chromosome association in species of the genus Aegilops

1992 ◽  
Vol 85-85 (2-3) ◽  
pp. 283-292 ◽  
Author(s):  
N. Cuñado
Keyword(s):  
Chromosome Association ◽  
Metaphase I

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.

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.

Meiotic chromosome association in diploid and tetraploid Avena strigosa Schrel.

Genome ◽  
1989 ◽  
Vol 32 (6) ◽  
pp. 972-977 ◽  
Author(s):  
S. N. Zadoo ◽  
R. N. Choubey ◽  
S. K. Gupta ◽  
J. Sybenga
Keyword(s):  
High Frequency ◽  
Meiotic Chromosome ◽  
Chromosome Association ◽  
Present Material ◽  
Negative Interference ◽  
Avena Strigosa ◽  
Partner Exchange ◽  
Quadrivalent Frequency ◽  
Chiasma Interference ◽  
Metaphase I

In diploid Avena strigosa the frequency and distribution of open (rod) bivalents suggest that a limited number of chromosomes, possibly two, fail to have a chiasma in one (short) arm in over 60% of the cells. In the tetraploid these are expected to form bivalents instead of quadrivalents at metaphase I of meiosis in a high frequency. In addition, interstitial chiasmata are expected in the long arms of these chromosomes, when involved in quadrivalents. In the tetraploid the frequency of quadrivalents is indeed low, and the configurations with interstitial chiasmata are distributed as expected. However, application of Sybenga's models suggests that the pairing system rather than the chiasma system would be responsible for the low quadrivalent frequency. It is suggested that apparent negative chiasma interference across the point of pairing partner exchange, resulting from variation in its location, invalidates application of these models to the present material. Negative interference results in an even higher than expected open bivalent frequency, in combination with a relatively high ring quadrivalent frequency. In addition, not only the subacrocentric chromosomes but also the more metacentric chromsomes, by this same mechanism, tend to form open bivalents more often than in the diploid.Key words: meiosis, bivalent, quadrivalent, diploid, tetraploid, Avena strigosa

A model of meiotic chromosome association in triploids

Genome ◽  
1989 ◽  
Vol 32 (1) ◽  
pp. 82-98 ◽  
Author(s):  
Charles F. Crane ◽  
David A. Sleper
Keyword(s):  
Genome Analysis ◽  
Meiotic Chromosome ◽  
A Priori ◽  
Chiasma Formation ◽  
Chromosome Association ◽  
Subsequent Formation ◽  
Meiotic Analysis ◽  
Partner Exchange ◽  
Translocation Heterozygosity ◽  
Metaphase I

A model was developed for chromosome association at meiotic metaphase I in triploids. Probabilities were estimated for each pachytene configuration and for subsequent formation of at least one chiasma in each combination of chromosome arms. Long and short arms were allowed to differ, but were related through an effective arm ratio so that the pattern of genomic affinity was the same for both arms. No other a priori assumptions were made about the pattern of genomic affinity. However, the usual assumptions of genome analysis were made including the following: identity of genomic-affinity pattern and chiasma frequency across homeologous groups, freedom from translocation heterozygosity, independence of chromosome arms, and absence of chiasma formation on both sides of a synaptic partner exchange within an arm. The model was statistically overparameterized and, therefore, had multiple solutions that yielded the same expected meiotic analysis. The range of these solutions can be found through repeated optimizations from randomly chosen starting values within the permitted ranges of the variables. It was convenient to express the optimized pattern of genomic affinity in terms of the proportions of metaphase I association due to each pairwise combination of genomes. Genomic affinity was analyzed in 16 triploid hybrids with the aid of the model.Key words: polyploidy, genome analysis, meiotic model.

A model of meiotic chromosome association in tetraploids

Genome ◽  
1989 ◽  
Vol 32 (4) ◽  
pp. 691-707 ◽  
Author(s):  
Charles F. Crane ◽  
David A. Sleper
Keyword(s):  
Meiotic Chromosome ◽  
A Priori ◽  
Meiotic Metaphase ◽  
Chromosome Association ◽  
Preferential Pairing ◽  
Subsequent Formation ◽  
Meiotic Analysis ◽  
Basic Assumptions ◽  
The Relationship ◽  
Metaphase I

A model is constructed for chromosome association at meiotic metaphase I in tetraploids. Probabilities are estimated for each pachytene configuration and for subsequent formation of at least one chiasma in each combination of chromosome arms. Long and short arms can differ but are related through an effective arm ratio so as to maintain the same pattern of genomic affinity for both arms. No other a priori assumptions are made about the pattern of genomic affinity, but the same basic assumptions are made as in our preceding model for triploids. The model is statistically overparameterized and therefore has multiple solutions whose range can be found through repeated optimization from different starting points. In some cases the same expected meiotic analysis can arise from quite different genomic structures, which therefore cannot be distinguished on the basis of unmarked chromosomes. Solutions to the model are conveniently expressed in terms of the proportion of metaphase I association due to each pairwise combination of genomes. Interpretation of model solutions is also aided by the use of numerical indices that reflect closeness to 11 particular genomic structures or that reveal properties of the relationship among variables. The model differs from that of Kimber and Alonso in its handling of two chiasmatically bound arms in a randomly pairing homologous group, and frequently as well in its optimized pattern of genomic affinity upon application to 3:1 and 2:1:1 genomic structures. With the aid of the model, genomic affinity is analyzed in 20 individuals, representing hybrids, amphiploids, and species.Key words: polyploidy, genome analysis, preferential pairing, meiotic model.

scholarly journals Chromosome differentiation and pairing behavior of polyploids: an assessment on preferential metaphase I associations in colchicine-induced autotetraploid hybrids within the genus Secale.

Genetics ◽  
1991 ◽  
Vol 128 (2) ◽  
pp. 433-442
Author(s):  
E Benavente ◽  
J Orellana
Keyword(s):  
Colchicine Treatment ◽  
Chromosome Association ◽  
Clear Relationship ◽  
Preferential Pairing ◽  
Chromosome Differentiation ◽  
Pairing Behavior ◽  
Parental Lines ◽  
Metaphase I

Abstract Preferential chromosome association at metaphase I has been analyzed and compared in autotetraploid cells obtained by colchicine treatment of hybrid diploid rye plants with different degrees of chromosomal divergence between homologs. The tendency to identical over homologous, but not identical, pairing preferences detected when homologous partners are contributed by less related parental lines indicates that chromosome differentiation may play an important role on preferential pairing behavior of polyploids. However, associations between more similar (identical) partners are not always favored, thus suggesting that additional factors must be considered. Other hypotheses for explaining pairing preferences in competitive situations are discussed. No clear relationship has been found between multivalent frequencies at metaphase I and chromosome differentiation between homologs or preferential pairing behavior. Therefore evolutionary divergences among related genomes should be carefully stated when evaluated from metaphase I configuration frequencies.

Chromosome Association in Mesostoma ehrenbergii (Focke) Schmidt

1939 ◽  
Vol 73 (745) ◽  
pp. 180-185 ◽  
Author(s):  
Ladley Husted ◽  
F. F. Ferguson ◽  
M. A. Stirewalt
Keyword(s):  
Chromosome Association
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