Homozygous and heterozygous homologous chromosomes: effects on preferential pairing and recombination frequency in wheat

Genome ◽  
1988 ◽  
Vol 30 (3) ◽  
pp. 336-340 ◽  
Author(s):  
E. Y. Suárez ◽  
L. Gorgoschidse ◽  
F. Sacco ◽  
H. Saione
Keyword(s):  
Genetic Analysis ◽  
Recombination Frequency ◽  
Preferential Pairing ◽  
Homologous Chromosomes ◽  
Positive Correlation

Trisomics for chromosomes 1A and 6B of wheat backcrossed to euploids showed progeny with unexpected segregation frequencies (cytological and genetical) that can be attributed to preferential pairing between homologues. Recombination frequency between the centromere and a gene for mildew reaction of chromosome 1A showed an increase from the first to the second backcross that could be attributed to a positive correlation between homozygosity and the degree of pairing between homologous chromosomes. The use of wheat trisomics for genetic analysis is also discussed.Key words: preferential pairing, trisomic segregation, wheat cytogenetics, recombination frequency, pathogen reaction.

Secondary Tetrasomic Segregation of MDH-B and Preferential Pairing of Homeologues in Rainbow Trout

Genetics ◽  
1997 ◽  
Vol 145 (4) ◽  
pp. 1083-1092 ◽  
Author(s):  
Fred W Allendorf ◽  
Roy G Danzmann
Keyword(s):  
Allelic Variation ◽  
Male Meiosis ◽  
Proximal Region ◽  
Stage Model ◽  
Preferential Pairing ◽  
Homologous Chromosomes ◽  
Tetrasomic Inheritance ◽  
Segregation Ratios ◽  
Homeologous Chromosomes ◽  
Duplicated Loci

We examined the inheritance of allelic variation at an isozyme locus, MDH-B, duplicated by ancestral polyploidy in salmonid fishes. We detected only disomic segregation in females. Segregation ratios in males were best explained by a mixture of disomic and tetrasomic inheritance. We propose a two-stage model of pairing in male meiosis in which, first, homologous chromosomes pair and recombine in the proximal region of the chromosome. Next, homeologous chromosomes pair and recombine distally. We suggest that this type of tetrasomic inheritance in which centromeres segregate disomically should be referred to as “secondary tetrasomy” to distinguish it from tetrasomy involving entire chromosomes (i.e., “primary tetrasomy”). Differences in segregation ratios between males indicate differences between individuals in the amount of recombination between homeologous chromosomes. We also consider the implication of these results for estimation of allele frequencies at duplicated loci in salmonid populations.

scholarly journals The intranuclear relationship between centromere volume and chromosome size in Festuca scariosa X drymeja

1981 ◽  
Vol 47 (1) ◽  
pp. 117-125
Author(s):  
G. Jenkins ◽  
M.D. Bennett
Keyword(s):  
Serial Section ◽  
Chromosome Length ◽  
Individual Chromosome ◽  
Chromosome Size ◽  
Preferential Pairing ◽  
Frequency Distributions ◽  
Positive Correlation ◽  
Serial Section Reconstruction

In the hybrid Festuca scarisoa X drymeja where pairing is incomplete at pachytene, there is preferential pairing between the longer chromosomes of the complement. EM serial-section reconstruction of nuclei at zygotene and pachytene reveals that there is equally pronounced preferential pairing between larger centromeres. This evidence suggests that the longer chromosomes have large centromeres and that centromere volume is correlated with chromosome length. Confirmation of this comes from the comparison of the frequency distributions of observed centromere volumes and those predicted on the basis of chromosome length. Although there is a positive correlation between centromere volume and chromosome length, it is not possible to identify the centromeres of each individual chromosome within the complement because (a) the differences between the lengths of each chromosome are small and (b) the estimates of relative centromere volumes vary significantly between cells.

scholarly journals ZYP1 is required for obligate cross-over formation and cross-over interference in Arabidopsis

2021 ◽  
Vol 118 (14) ◽  
pp. e2021671118
Author(s):  
Martin G. France ◽  
Janina Enderle ◽  
Sarah Röhrig ◽  
Holger Puchta ◽  
F. Chris H. Franklin ◽  
...  
Keyword(s):  
Genetic Analysis ◽  
Synaptonemal Complex ◽  
Class Ii ◽  
Class I ◽  
Crossing Over ◽  
Wild Type ◽  
Homologous Chromosomes ◽  
Virtual Absence ◽  
Meiotic Progression ◽  
Null Mutants

The synaptonemal complex is a tripartite proteinaceous ultrastructure that forms between homologous chromosomes during prophase I of meiosis in the majority of eukaryotes. It is characterized by the coordinated installation of transverse filament proteins between two lateral elements and is required for wild-type levels of crossing over and meiotic progression. We have generated null mutants of the duplicated Arabidopsis transverse filament genes zyp1a and zyp1b using a combination of T-DNA insertional mutants and targeted CRISPR/Cas mutagenesis. Cytological and genetic analysis of the zyp1 null mutants reveals loss of the obligate chiasma, an increase in recombination map length by 1.3- to 1.7-fold and a virtual absence of cross-over (CO) interference, determined by a significant increase in the number of double COs. At diplotene, the numbers of HEI10 foci, a marker for Class I interference-sensitive COs, are twofold greater in the zyp1 mutant compared to wild type. The increase in recombination in zyp1 does not appear to be due to the Class II interference-insensitive COs as chiasmata were reduced by ∼52% in msh5/zyp1 compared to msh5. These data suggest that ZYP1 limits the formation of closely spaced Class I COs in Arabidopsis. Our data indicate that installation of ZYP1 occurs at ASY1-labeled axial bridges and that loss of the protein disrupts progressive coalignment of the chromosome axes.

scholarly journals Genome Duplication Increases Meiotic Recombination Frequency: A Saccharomyces cerevisiae Model

2020 ◽  
Author(s):  
Ou Fang ◽  
Lin Wang ◽  
Yuxin Zhang ◽  
Jixuan Yang ◽  
Qin Tao ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Meiotic Recombination ◽  
Genome Stability ◽  
Genome Duplication ◽  
Genetic Recombination ◽  
Recombination Frequency ◽  
Abiotic Factors ◽  
Strand Break ◽  
Homologous Chromosomes ◽  
Almost All

Abstract Genetic recombination characterized by reciprocal exchange of genes on paired homologous chromosomes is the most prominent event in meiosis of almost all sexually reproductive organisms. It contributes to genome stability by ensuring the balanced segregation of paired homologs in meiosis, and it is also the major driving factor in generating genetic variation for natural and artificial selection. Meiotic recombination is subjected to the control of a highly stringent and complex regulating process and meiotic recombination frequency (MRF) may be affected by biological and abiotic factors such as sex, gene density, nucleotide content, and chemical/temperature treatments, having motivated tremendous researches for artificially manipulating MRF. Whether genome polyploidization would lead to a significant change in MRF has attracted both historical and recent research interests; however, tackling this fundamental question is methodologically challenging due to the lack of appropriate methods for tetrasomic genetic analysis, thus has led to controversial conclusions in the literature. This article presents a comprehensive and rigorous survey of genome duplication-mediated change in MRF using Saccharomyces cerevisiae as a eukaryotic model. It demonstrates that genome duplication can lead to consistently significant increase in MRF and rate of crossovers across all 16 chromosomes of S. cerevisiae, including both cold and hot spots of MRF. This ploidy-driven change in MRF is associated with weakened recombination interference, enhanced double-strand break density, and loosened chromatin histone occupation. The study illuminates a significant evolutionary feature of genome duplication and opens an opportunity to accelerate response to artificial and natural selection through polyploidization.

Light and electron microscope observations of a meiotic mutant of Neurospora crassa

1978 ◽  
Vol 56 (21) ◽  
pp. 2694-2706 ◽  
Author(s):  
B.C. Lu ◽  
Donna R. Galeazzi
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Genetic Analysis ◽  
Neurospora Crassa ◽  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Light And Electron Microscopy ◽  
Homologous Chromosomes ◽  
Synaptonemal Complexes ◽  
Nuclear Separation

Light and electron microscopy have revealed that the meiotic-1 (mei-1) mutant of Neurospora crassa is defective in chromosome pairing (asynaptic) although plenty of axial components of the synaptonemal complex are produced and occasional tripartite synaptonemal complexes can be formed. The mei-1 mutant is most probably defective in bringing the homologous chromosomes together for pairing and for assembly of the synaptonemal complex. The mei-1 mutant is also defective in nuclear separation which leads to a four-poled spindle at the subsequent division. The lack of chromosome pairing, the incomplete assembly of the synaptonemal complex, and the four-poled spindles account for absence of recombination and for the nondisjunction found in genetic analysis.

Cytogenetic analyses of intersectional hybrids between Parthenium argentatum and Parthenium confertum

Genome ◽  
1989 ◽  
Vol 32 (1) ◽  
pp. 134-140 ◽  
Author(s):  
A. Hashemi ◽  
A. Estilai ◽  
J. G. Waines
Keyword(s):  
Natural Rubber ◽  
Growth Habit ◽  
Backcross Progeny ◽  
Woody Species ◽  
Herbaceous Species ◽  
Parthenium Argentatum ◽  
Preferential Pairing ◽  
Homologous Chromosomes ◽  
Multivalent Formation ◽  
Cytogenetic Analyses

Induced tetraploid guayule (Parthenium argentatum Gray, a rubber-producing and woody species of section Parthenicaeta) was crossed to P. confertum var. lyratum Gray, a herbaceous species of section Argyrocheta. Hybrids were obtained when guayule was used as female. Like their diploid progenitors, induced tetraploids were sexual and self-incompatible. At meiosis, they averaged 0.30 I, 29.63 II, 0.12 III, and 3.02 IV. Parthenium confertum had 69 chromosomes and was apomictic. At meiosis, it averaged 1.00 I, 32.98 II, and 0.51 IV. Hybrids received 36 chromosomes from guayule and 34 chromosomes from P. confertum. At meiosis, they averaged 0.52 I, 33.44 II, 0.20 III, and 0.50 IV. F1 plants behaved like an amphidiploid in which homologous chromosomes of guayule genome paired with each other and homologous chromosomes of P. confertum genome also paired preferentially. Chromosome association in the hybrids indicated that P. confertum parent may be a tetraploid with suppressed multivalent formation. Although hybrids were partially fertile and produced backcross progeny, the transfer of desirable traits (rapid growth and herbaceous growth habit) from P. confertum into guayule will depend on elimination of preferential pairing in the hybrids.Key words: guayule, natural rubber, meiosis, chromosome pairing.

Diploid-like meiotic behavior in synthesized amphiploids of the genus Glycine Willd. subgenus Glycine

1985 ◽  
Vol 27 (6) ◽  
pp. 655-660 ◽  
Author(s):  
R. J. Singh ◽  
T. Hymowitz
Keyword(s):  
Chromosomal Instability ◽  
Interspecific Hybrids ◽  
Meiotic Behavior ◽  
Preferential Pairing ◽  
Homologous Chromosomes ◽  
Tetraploid Hybrid

Six amphiploids consisting of one allotetraploid (2n = 4x = 80), four allohexaploids (2n = 6x = 120), and one allooctoploid (2n = 8x = 160) were synthesized by doubling the chromosomes of F1 interspecific hybrids of the following parents: one diploid (Glycine latifolia 2n = 2x = 40 × G. clandestina, short pod (Sp), 2n = 2x = 40); four triploids (G. clandestina, Sp, 2n = 2x = 40 × G. tabacina 2n = 4x = 80), (G. tabacina 2n = 4x = 80 × G. canescens 2n = 2x = 40), (G. tomentella2n = 4x = 80 × G. canescens 2n = 2x = 40 and its reciprocal); and one tetraploid (G. tomentella2n = 4x = 80 × G. tabacina 2n = 4x = 80). Chromosomal chimerism was observed in the C1 generation. Pod set was recorded in all the colchicine-treated hybrids except in the tetraploid hybrid of G. tomentella × G. tabacina. In C2 generation plants, chromosomal instability was noticed only in the allohexaploid of G. tabacina × G. canescens. All of the amphiploids showed diploid-like meiosis in the majority of the sporocytes and did not exhibit expected multivalent associations, a classical example of allopolyploidy. This was attributed to strong preferential pairing between homologous chromosomes which may be under genetic control.Key words: Glycine, synapsis, interspecific hybrids.

Conserved patterns of chromosome pairing and recombination in Brassica napus crosses

Genome ◽  
1997 ◽  
Vol 40 (4) ◽  
pp. 496-504 ◽  
Author(s):  
I. A. P. Parkin ◽  
D. J. Lydiate
Keyword(s):  
Brassica Napus ◽  
Oilseed Rape ◽  
Chromosome Pairing ◽  
Recombination Frequency ◽  
Microspore Culture ◽  
Genetic Maps ◽  
Winter Oilseed Rape ◽  
Homologous Chromosomes ◽  
Novel Alleles ◽  
Two Populations

The patterns of chromosome pairing and recombination in two contrasting Brassica napus F1 hybrids were deduced. One hybrid was from a winter oilseed rape (WOSR) × spring oilseed rape cross, the other from a resynthesized B. napus × WOSR cross. Segregation at 211 equivalent loci assayed in the population derived from each hybrid produced two collinear genetic maps. Alignment of the maps indicated that B. napus chromosomes behaved reproducibly as 19 homologous pairs and that the 19 distinct chromosomes of B. napus each recombined with unique chromosomes from the interspecific hybrid between Brassica rapa and Brassica oleracea. This result indicated that the genomes of the diploid progenitors of amphidiploid B. napus have remained essentially unaltered since the formation of the species and that the progenitor genomes were similar to those of modern-day B. rapa and B. oleracea. The frequency and distribution of crossovers were almost indistinguishable in the two populations, suggesting that the recombination machinery of B. napus could cope easily with different degrees of genetic divergence between homologous chromosomes. Efficient recombination in wide crosses will facilitate the introgression of novel alleles into oilseed rape from B. rapa and B. oleracea (via resynthesized B. napus) and reduce linkage drag.Key words: integrating genetic maps, microspore culture, segregation distortion, recombination frequency, locus distribution.

Gene segregation in induced tetraploid rainbow trout: genetic evidence of preferential pairing of homologous chromosomes

Genome ◽  
1988 ◽  
Vol 30 (4) ◽  
pp. 547-553 ◽  
Author(s):  
A. Diter ◽  
R. Guyomard ◽  
D. Chourrout
Keyword(s):  
Rainbow Trout ◽  
Genetic Evidence ◽  
Salmo Gairdneri ◽  
Preferential Pairing ◽  
Homologous Chromosomes ◽  
Tetrasomic Inheritance ◽  
Gene Segregation ◽  
Sib Families ◽  
Males And Females ◽  
Homoeologous Chromosomes

Gene segregation at six protein loci was analysed in progeny from tetraploid males and females obtained by suppression of first mitosis. The triploid full-sib families from five tetraploid males and the diploid gynogenetic lines from four tetraploid females were examined. The proportions of heterozygous gametes (0.83 on the average) were significantly higher than expected from tetrasomic inheritance (0.667) at all the loci studied. This was explained by preferential pairing of homologous chromosomes. The proportions of heterozygous gametes were significantly different between loci, but the variations were not correlated with the gene–centromere distances. Our results showed that, at least for one locus, the homozygous gametes mainly resulted from pairing of homoeologous chromosomes rather than from pairing of homologous chromosomes, quadrivalent formation, and chromatin exchanges between homoeologous chromosomes.Key words: Salmo gairdneri richardson, induced tetraploidy, gene segregation, electrophoresis.

scholarly journals Regional Bivalent-Univalent Pairing Versus Trivalent Pairing of a Trisomic Chromosome in Saccharomyces cerevisiae

Genetics ◽  
1996 ◽  
Vol 144 (3) ◽  
pp. 957-966 ◽  
Author(s):  
Antonius Koller ◽  
Joseph Heitman ◽  
Michael N Hall
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Yeast Strain ◽  
Meiotic Pairing ◽  
Preferential Pairing ◽  
Homologous Chromosomes ◽  
Complete Set ◽  
Meiosis I

Abstract In meiosis I, homologous chromosomes pair, recombine and segregate to opposite poles. These events and subsequent meiosis I1 ensure that each of the four meiotic products has one complete set of chromosomes. In this study, the meiotic pairing and segregation of a trisomic chromosome in a diploid (2n + 1) yeast strain was examined. We find that trivalent pairing and segregation is the favored arrangement. However, insertions near the centromere in one of the trisomic chromosomes leads to preferential pairing and segregation of the “like” centromeres of the remaining two chromosomes, suggesting that bivalent-univalent pairing and segregation is favored for this region.

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