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.

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 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.

Undifferentiated sex chromosomes in Mastotermes darwiniensis Froggatt (Isoptera; Mastotermitidae) and the evolution of eusociality in termites

Genome ◽  
1987 ◽  
Vol 29 (1) ◽  
pp. 76-79 ◽  
Author(s):  
D. G. Bedo
Keyword(s):  
Key Words ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Mitotic Metaphase ◽  
Evolution Of Sex ◽  
Termite Species ◽  
Chromosome Differentiation ◽  
Evolution Of Eusociality ◽  
Metaphase I

Meiosis and mitosis was studied in males of the primitive termite Mastotermes darwiniensis, which is closely related to the Dictyoptera. In mitotic metaphase cells 98 chromosomes were found with a matching 49 bivalents at metaphase I. Mastotermes darwiniensis has a largely acrocentric karyotype with no sex-linked translocation complexes, like those found in many other termite species, or other sex chromosome differentiation. These observations suggest that ancestral termites probably had karyotypes with many small chromosomes lacking sex chromosome differentiation and that there is no connection between the evolution of sex-linked translocation complexes and eusociality. Key words: sex chromosomes, Mastotermes, termites, eusociality.

Chromosome pairing in hybrids of ph1b mutant wheat with rye

Genome ◽  
1988 ◽  
Vol 30 (5) ◽  
pp. 639-646 ◽  
Author(s):  
T. Naranjo ◽  
A. Roca ◽  
R. Giraldez ◽  
P. G. Goicoechea
Keyword(s):  
Common Wheat ◽  
Chromosome Pairing ◽  
Chromosome Structure ◽  
Preferential Pairing ◽  
C Banding ◽  
Homoeologous Chromosomes ◽  
Metaphase I

Metaphase I pairing was studied in five ph1b mutant wheat × rye hybrids to verify the presence of translocations between homoeologous chromosomes in ph1b mutant wheat and to establish the pairing homoeology between wheat and rye chromosomes. Three 5B-deficient ABDR hybrids with standard chromosome structure were used as controls. Chromosomes 1R and 5R of rye and most wheat chromosomes, as well as their arms, were identified by means of C-banding. The presence of 5BS in ph1b hybrids raised the overall pairing level. The pattern of pairing between wheat chromosomes in ph1b hybrids, as in 5B-deficient hybrids, was characterized by the occurrence of preferential pairing between chromosomes of the A and D genomes in most homoeologous groups. The existence of a double translocation involving 4BL, 5AL, and 7BS in common wheat was confirmed. Deviation from the standard pairing pattern suggested the existence of a translocation involving 1BL and 1DL in one ph1b ABDR plant and another translocation involving 3AL and 3DL in three other ph1b hybrids. In ph1b hybrids, wheat – rye pairing was relatively frequent for 1RL, 5RL, and an arm of a metacentric rye chromosome, probably 2R, that is homoeologous to 2BL, and the homoeologous arms of 2A and 2D. The existence of a translocation involving 5RL and 4RL in rye was confirmed.Key words: homoeologous, homologous, 5B-deficient, translocations, C-banding.

scholarly journals Morphology and Meiotic Behavior of Three Dendrobium Amphidiploids and Their Diploid Counterparts

HortScience ◽  
1993 ◽  
Vol 28 (9) ◽  
pp. 935-937 ◽  
Author(s):  
James McConnell ◽  
H. Kamemoto
Keyword(s):  
Small Chromosome ◽  
Chromosome Size ◽  
Meiotic Behavior ◽  
Preferential Pairing ◽  
Bivalent Formation ◽  
Metaphase I

Floral characteristics, meiotic behavior, and sporad formation were compared in three Dendrobium tetraploids (amphidiploids) and their diploid counterparts. Amphidiploid flowers were larger than those of diploids. Diploid meiotic behavior varied; mean configurations at Metaphase I ranged from 14.3 bivalents and 9.4 univalents to 18.9 bivalents and 0.2 univalents. In amphidiploids, nearly all cells had 38 bivalents. Sporad formation also varied; diploids had 36% to 70% tetrads and amphidiploids had 97% to 100% tetrads. Preferential pairing and small chromosome size may promote bivalent formation in amphidiploids.

The effect of colchicine on fibrillar material in wheat meiocytes

1979 ◽  
Vol 38 (1) ◽  
pp. 33-47 ◽  
Author(s):  
M.D. Bennett ◽  
J.B. Smith
Keyword(s):  
Colchicine Treatment ◽  
Microtubule Assembly ◽  
Fibrillar Material ◽  
Sensitive Stage ◽  
Metaphase I

Wheat meiocytes contain intranuclear bundles of microfibres at stages from pre-meiotic mitosis until zygotene. This includes early pre-meiotic interphase, the stage when colchicine induces univalents at subsequent metaphase I. This paper reports the effect of colchicine on the structure and distribution of such fibrillar material. Many normal-looking bundles of intranuclear fibrillar material formed after prolonged colchicine treatment (up to 5 days) which totally suppressed microtubule assembly in meiocytes. Thus, fibrillar material is unlikely to comprise tubulin. However, the formation of intranuclear fibrillar material was retarded in colchicine-treated meiocytes, and fibrillar material was absent during the colchicine-sensitive stage for univalency. The occurrence of cytoplasmic fibrillar material was delayed and greatly increased in colchicine-treated meiocytes compared with controls. A novel curved form of fibrillar material was seen in colchicine-treated meiocytes. It is concluded that colchicine had significant effects on the assembly and distribution of fibrillar material. These results are, therefore, compatible with the possibility that colchicine causes univalency in wheat via its effects on fibrillar material.

Amphidiploids of perennial Triticeae. I. Synthetic Thinopyrum species and their hybrids

Genome ◽  
1992 ◽  
Vol 35 (6) ◽  
pp. 951-956 ◽  
Author(s):  
Richard R.-C. Wang
Keyword(s):  
Gene Flow ◽  
Chromosome Pairing ◽  
Colchicine Treatment ◽  
Meiotic Pairing ◽  
Pseudoroegneria Spicata ◽  
Genomic Relationships ◽  
Thinopyrum Elongatum ◽  
Metaphase I

Amphiploids of the hybrid Thinopyrum elongatum (Host) D.R. Dewey (2n = 2x = 14; JeJe) × Pseudoroegneria spicata (Pursh) A. Löve (2n = 2x = 14; SS) were obtained by the colchicine treatment of regenerants from inflorescence culture. Meiotic pairings in the JJSS amphiploids averaged 2.90 I + 4.44 rod II + 7.50 ring II + 0.14 III + 0.20 IV at metaphase I but had 13.38 ring II + 0.30 IV at diakinesis. This amphidiploid was crossed with that of T. bessarabicum (Savul. &Rayss) A. Löve (2n = 2x = 14; JbJb) × T. elongatum and the latter was also crossed with T. scirpeum (K. Presl) D.R. Dewey (2n = 4x = 28; JeJeJeJe) to obtain JbJeJeS and JeJeJeJb hybrids, respectively. The former hybrid had a metaphase I pairing pattern of 7.82 I + 4.33 rod II + 2.76 ring II + 1.51 III + 0.35 IV. The latter hybrid had 3.04 I + 4.05 rod II + 4.31 ring II + 1.26 III + 1.08 IV. These meiotic pairing data are in agreement with the genomic relationships based on the diploid hybrids involving these genomes. Fertility of the hybrid between T. scirpeum and the amphiploid of T. bessarabicum × T. elongatum suggested that their genomes were similar and balanced and that gene flow could occur between the JJ diploids and the JJJJ tetraploid.Key words: hybrid, amphidiploid, genome, isozyme, chromosome pairing, Triticeae, Thinopyrum.

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