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.

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 Distinct prophase arrest mechanisms in human male meiosis

2017 ◽  
Author(s):  
Sabrina Z. Jan ◽  
Aldo Jongejan ◽  
Cindy M. Korver ◽  
Saskia K. M. van Daalen ◽  
Ans M. M. van Pelt ◽  
...  
Keyword(s):  
Genomic Stability ◽  
Male Meiosis ◽  
Type I ◽  
Type Ii ◽  
Meiotic Arrest ◽  
Homologous Chromosomes ◽  
Xy Body ◽  
Chromosome Synapsis ◽  
Human Male ◽  
Meiotic Crossover

To prevent chromosomal aberrations to be transmitted to the offspring, strict meiotic checkpoints are in place to remove aberrant spermatocytes. However, in about 1% of all males these checkpoints cause complete meiotic arrest leading to azoospermia and subsequent infertility. We here unravel two clearly distinct meiotic arrest mechanisms that act during the prophase of human male meiosis. Type I arrested spermatocytes display severe asynapsis of the homologous chromosomes, disturbed XY-body formation and increased expression of the Y-chromosome encoded gene ZFY and seem to activate a DNA damage pathway leading to induction of p63 mediated spermatocyte elimination. Type II arrested spermatocytes display normal chromosome synapsis, normal XY-body morphology and meiotic crossover formation but have a lowered expression of several cell cycle regulating genes and fail to properly silence the X-chromosome encoded gene ZFX. Discovery and understanding of these meiotic arrest mechanisms increases our knowledge on how genomic stability is guarded during human germ cell development.

scholarly journals Mutations in Caenorhabditis elegans him-19 Show Meiotic Defects That Worsen with Age

2010 ◽  
Vol 21 (6) ◽  
pp. 885-896 ◽  
Author(s):  
Lois Tang ◽  
Thomas Machacek ◽  
Yasmine M. Mamnun ◽  
Alexandra Penkner ◽  
Jiradet Gloggnitzer ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Male Meiosis ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Homologous Chromosomes ◽  
Recombination Protein ◽  
High Incidence ◽  
Bivalent Formation ◽  
Synaptonemal Complex Formation

From a screen for meiotic Caenorhabditis elegans mutants based on high incidence of males, we identified a novel gene, him-19, with multiple functions in prophase of meiosis I. Mutant him-19(jf6) animals show a reduction in pairing of homologous chromosomes and subsequent bivalent formation. Consistently, synaptonemal complex formation is spatially restricted and possibly involves nonhomologous chromosomes. Also, foci of the recombination protein RAD-51 occur delayed or cease altogether. Ultimately, mutation of him-19 leads to chromosome missegregation and reduced offspring viability. The observed defects suggest that HIM-19 is important for both homology recognition and formation of meiotic DNA double-strand breaks. It therefore seems to be engaged in an early meiotic event, resembling in this respect the regulator kinase CHK-2. Most astonishingly, him-19(jf6) hermaphrodites display worsening of phenotypes with increasing age, whereas defects are more severe in female than in male meiosis. This finding is consistent with depletion of a him-19-dependent factor during the production of oocytes. Further characterization of him-19 could contribute to our understanding of age-dependent meiotic defects in humans.

scholarly journals INCIPIENT GENOME DIFFERENTIATION IN GOSSYPIUM. III. COMPARISON OF CHROMOSOMES OF G. HIRSUTUM AND ASIATIC DIPLOIDS USING HETEROZYGOUS TRANSLOCATIONS

Genetics ◽  
1982 ◽  
Vol 100 (1) ◽  
pp. 89-103
Author(s):  
Margaret Y Menzel ◽  
Clare A Hasenkampf ◽  
James McD Stewart
Keyword(s):  
Upland Cotton ◽  
Diploid Species ◽  
Standard Line ◽  
Preferential Pairing ◽  
D Genome ◽  
Reciprocal Translocations ◽  
Genome Constitution ◽  
Naturally Occurring ◽  
A Genome ◽  
Segregation Ratios

ABSTRACT Hybrids between upland cotton (G. hirsutum, genome constitution 2AhDh) and either A-genome or D-genome diploid species exhibit 26 paired and 13 unpaired chromosomes at metaphase I. The Ah and Dh genomes are therefore considered homoeologous with those of the respective diploids. Previous studies, nevertheless, revealed a low level of ("incipient") differentiation between Dh and various diploid D genomes. The diploid A genomes have been regarded as more closely homologous to Ah on the basis of low preferential pairing and autotetraploid segregation ratios in allohexaploids.—The present study addressed the following questions: Are the diploid A genomes differentiated from Ah in meiotic homology? If so, is the differentiation manifested equally by all 13 chromosomes or is it localized in certain chromosomes?—Three diploid A-genome lines representing G. herbaceum and G. arboreum were hybridized by in ovulo culture of embryos (1) with a standard line of G. hirsutum, which differs from G. herbaceum by two and from G. arboreum by three naturally occurring reciprocal translocations involving chromosomes 1—5, and (2) with six lines homozygous for experimental translocations involving chromosomes 6, 7, 10, 11, 12 and 13. Chiasma frequencies in hybrids were compared with those in appropriate G. hirsutum controls. In every comparison overall chiasma frequencies were slightly lower in the hybrids. Therefore Ah appears to be differentiated from the diploid A genomes. No localized differentiation was detected in chromosomes marked by experimental translocations. The differentiation may be localized mainly in chromosomes 4 and 5.

Inheritance patterns in hybrids between Sorghum almum Parodi and perennial sweet Sudan grass

1965 ◽  
Vol 16 (4) ◽  
pp. 525 ◽  
Author(s):  
AJ Pritchard
Keyword(s):  
Genetic Control ◽  
Segregation Ratio ◽  
Preferential Pairing ◽  
Inheritance Patterns ◽  
Tetrasomic Inheritance ◽  
Sudan Grass ◽  
Meiotic Stability ◽  
Plant Colour

Juicy stem and brown plant colour are mainly tetrasomically inherited in hybrids between Sorghum almum (2n = 40) and perennial sweet Sudan grass (2n = 40). Tetrasomic inheritance is also indicated for weak midrib development and dwarf habit. The juicy stem and brown plant colour characters are linked, and the chromosomes on which these genes are situated may pair preferentially and give a 15 : 1 segregation ratio, instead of pairing at random and giving a tetrasomic segregation ratio of 35 : 1. The capacity of these chromosomes to pair preferentially may be under genetic control. It is possible that preferential pairing is part of a general diploidization process, which has led to a reduction in quadrivalent formation and increased meiotic stability in the tetraploid sorghums.

INHERITANCE OF BRANCHED RACEME AND CAULIFLOWER CHARACTERS IN ALFALFA

1982 ◽  
Vol 24 (5) ◽  
pp. 485-492 ◽  
Author(s):  
Toshiro Kinoshita ◽  
Ken-Ichi Suginobu
Keyword(s):  
Inheritance Patterns ◽  
Tetrasomic Inheritance ◽  
Test Cross ◽  
Medicago Saliva ◽  
Segregation Ratios ◽  
Segregating Population

The inheritance of the branched raceme character in alfalfa (Medicago saliva L.) was studied. In the segregation of inflorescence types, the cauliflower type with vestigial flowers appeared in the segregating population together with the branched raceme and normal types. According to the inheritance patterns observed in F2, F3, F4 and test cross, it was postulated that a single recessive tetrasomically inherited gene is responsible for both types of inflorescence; the genotypes for branched raceme and cauliflower types were designated as simplex (Aaaa) and nulliplex (aaaa), respectively. Various segregation ratios obtained in the progenies from inter-crossings and backcrossings were explained consistently due to the possible combination of the genotypes used for the parents. Test crossings between cauliflower and normal types also demonstrated the simple tetrasomic inheritance in F2 populations under random chromosome assortment. It was determined that the branched raceme character used for the experiments possesses the heterozygous simplex genotype (Aaaa).

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.

PREFERENTIAL PAIRING OF CHROMOSOMES IN A TETRAPLOID HYBRID BETWEEN ORYZA GLABERRIMA AND O. SATIVA

1968 ◽  
Vol 10 (3) ◽  
pp. 527-535 ◽  
Author(s):  
Hiko-Ichi Oka
Keyword(s):  
Oryza Sativa ◽  
Oryza Sativa L ◽  
Oryza Glaberrima ◽  
Tetraploid Species ◽  
Preferential Pairing ◽  
Tetraploid Hybrid ◽  
Segregation Ratios ◽  
Gametic Selection ◽  
High Degree ◽  
Species Hybrids

A tetraploid hybrid was obtained from a cross between induced tetraploid strains of Oryza sativa L. and O. glaberrima Steud., which differed in glutinous (waxy) vs. non-glutinous starch (gl: +) and other genes. In the hybrid, as compared with the parental strains, there was a reduced number of quadricvalents and a relatively high degree of fertility. Segregation ratios for the glutinous gene observed in the back-cross and F2 generation appeared to be modified not only by preferential homogenetic pairing but also by gametic selection. Taking into account the effect of gametic selection estimated from simplex heterozygotes, it was suggested that preferential pairing could take place to a certain extent. It seems to be difficult to measure quantitatively the degree of preferential pairing in tetraploid species hybrids, unless the effect of various segregation-distorting factors can be accounted for.

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.

scholarly journals Isolation and Cytogenetic Characterization of Male Meiotic Mutants of Drosophila melanogaster

Genetics ◽  
2004 ◽  
Vol 166 (4) ◽  
pp. 1795-1806
Author(s):  
Kazuyuki Hirai ◽  
Satomi Toyohira ◽  
Takashi Ohsako ◽  
Masa-Toshi Yamamoto
Keyword(s):  
Drosophila Melanogaster ◽  
Sex Chromosome ◽  
Male Meiosis ◽  
Fourth Chromosome ◽  
Homologous Chromosomes ◽  
Meiotic Mutants ◽  
Chromatid Cohesion ◽  
Cytogenetic Characterization ◽  
Meiosis I

Abstract Proper segregation of homologous chromosomes in meiosis I is ensured by pairing of homologs and maintenance of sister chromatid cohesion. In male Drosophila melanogaster, meiosis is achiasmatic and homologs pair at limited chromosome regions called pairing sites. We screened for male meiotic mutants to identify genes required for normal pairing and disjunction of homologs. Nondisjunction of the sex and the fourth chromosomes in male meiosis was scored as a mutant phenotype. We screened 2306 mutagenized and 226 natural population-derived second and third chromosomes and obtained seven mutants representing different loci on the second chromosome and one on the third. Five mutants showed relatively mild effects (<10% nondisjunction). mei(2)yh149 and mei(2)yoh7134 affected both the sex and the fourth chromosomes, mei(2)yh217 produced possible sex chromosome-specific nondisjunction, and mei(2)yh15 and mei(2)yh137 produced fourth chromosome-specific nondisjunction. mei(2)yh137 was allelic to the teflon gene required for autosomal pairing. Three mutants exhibited severe defects, producing >10% nondisjunction of the sex and/or the fourth chromosomes. mei(2)ys91 (a new allele of the orientation disruptor gene) and mei(3)M20 induced precocious separation of sister chromatids as early as prometaphase I. mei(2)yh92 predominantly induced nondisjunction at meiosis I that appeared to be the consequence of failure of the separation of paired homologous chromosomes.

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