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  • 1
    Publication Date: 1983-06-10
    Description: Hybridization between two chromosomally distinct subspecies of the grasshopper Caledia captiva results in a high incidence of novel chromosomal rearrangements among the backcross progeny. Rearrangements are restricted to those chromosomes derived from the F1 hybrid parent. Chromosomal involvement is nonrandom with the same rearrangement occurring repeatedly in different backcrosses. A single individual can also generate an array of different rearrangements among its offspring. Several of the rearrangements have also been found in natural populations. The nonrandom and recurrent nature of these chromosomal mutations at high frequencies provides a plausible explanation for the establishment and fixation of chromosomal rearrangements in natural populations.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shaw, D D -- Wilkinson, P -- Coates, D J -- New York, N.Y. -- Science. 1983 Jun 10;220(4602):1165-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6407107" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biological Evolution ; Chromosomes/*physiology ; Drosophila melanogaster ; Female ; Genetic Variation ; Grasshoppers/*genetics ; *Hybridization, Genetic ; Male ; *Mutation
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 86 (1982), S. 509-531 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A comparison of chiasma distribution patterns between two chromosomal taxa, Moreton and Torresian, and their F1 hybrids demonstrates highly significant differences between all chromosomes analysed. In chromosomes 1, 2, 4, 5, 6 and 8 these differences can be directly attributed to pericentric heterozygosity in the F1 hybrid. In chromosomes 7 and 8 where there is no pericentric heterozygosity these differences may be due to heterozygosity for interstitial and terminal bands of hetero-chromatin or possibly undetected paracentric rearrangements. The F1 hybrids also have a significantly lower mean cell chiasma frequency. The Moreton and Torresian taxa differ significantly in chiasma distribution pattern in chromosomes 1, 2, 4, 5, 6 and 8 and both Moreton populations analysed have a significantly lower mean cell chiasma frequency than the Torresian population. In addition the two Moreton populations, (MMX) and (MAX), differ significantly in the chiasma distribution pattern in chromosomes 1 and 2 and the chromosomally more polymorphic population (MMX) has a significantly lower mean cell chiasma frequency. There is some evidence that the differences in both chiasma distribution and frequency between these two populations may be due to genetic differences in addition to the effects caused by chromosomal polymorphism. It has been shown that in general there is a substantial reduction in recombination in the intersitial regions of most chromosomes in the Moreton and particularly the Torresian taxon because of a proximal-distal localisation of chiasmata. In the F1 hybrid, however, nearly all recombination events are located within these interstitial regions. This provides support for the hypothesis that the frequent placement of chiasmata in regions of normally low recombination may disrupt the internal coadapted genetic environment of both chromosomal forms resulting in non-functional recombinant progeny in the next generation. The recombination data in this study also provide a basis for an empirical test of this hypothesis.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 86 (1982), S. 533-549 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract An analysis of the relative viabilities of recombinant and nonrecombinant chromosomes among the surviving embryos from back-crosses involving the Moreton (M) and Torresian (T) taxa has revealed that these embryos do not contain a representative sample of gametes derived from the F1 hybrid parent. The significant deviations in the hybrid gametic population arise entirely from intrachromosomal effects with no evidence of any between-chromosome interactions. This is interpreted as clear evidence to show that recombinational repatterning within heterozygous bivalents in the F1 parent is a significant factor in inducing the observed deviant segregation ratios. Furthermore, by using a population which is chromosomally equivalent to the Torresian but genically similar to the Moreton, it has been shown that over 46% of the F2 embryonic breakdown arises solely from the effects of chromosomal heterozygosity upon recombination repatterning among (Moreton × Torresian) F1 hybrids. From these data it is proposed that each chromosome is internally coadapted in the sense that it contains balanced blocks of cis-acting acting loci which can be disrupted by recombinational change. Disruption of the linear association of the genes on structurally different chromosomes by recombination repatterning results in novel intrachromosomal associations which may be functionally inadequate and so lead to arrested embryonic development. It is speculated that an important factor in arresting development may involve interactions between the novel recombinant chromosomes of the gamete and maternal factors laid down in the egg during oogenesis which are responsible for the sequential activation of the genomes of the progeny during development. Thus coadaptation is interpreted in terms of the functional intergration of a chromosome with the products of the genome of the previous generation. The assessment of the relative viabilities of recombinant and nonrecombinant chromosomes has shown that the Torresian nonrecombinant chromosomes possess the highest viabilities in the sequence TN〉MN≧TR = MR where N and R represent nonrecombinant and recombinant classes. This sequence is relevant to the structure of the hybrid zone between the Torresian and Moreton taxa and explains both its asymmetry and the basis of the observed introgression of Torresian chromosomes into the Moreton taxon and the absence of the reverse movement.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The spatial distribution of chromosomes has been analysed in radial metaphase neuroblast cells in F1 hybrid embryos generated by crossing individuals of the Moreton and Torresian (TT) chromosomal taxa of the grasshopper Caledia captiva. The Moreton individuals were of two kinds depending on whether they carried an acrocentric X (MAX) or a metacentric X (MMX). No significant associations were detected between any pair of homologous chromosomes in either male or female (MAX x TT) and (MMX x TT) F1 hybrids. This result was supported by data which showed that the mean separation between homologues is greater, although not significantly so, than the mean separation between non-homologous chromosomes within the two Moreton genomes. Indeed, in a number of cases, genome separation was clearly observed in radial metaphase preparations from these F1 hybrids. By comparison the analysis of pairwise associations between non-homologous chromosomes within the MMX and MAX Moreton genomes revealed a number of significant associations and dissociations which strongly suggests that at least some chromosomes in these genomes are organised non-randomly at metaphase. Of particular interest was the highly significant X-5 association in the MMX genome since in a previous study X-5 rearrangements were found to occur repeatedly among different backcross progeny involving Moreton x Torresian F1 hybrids. Additionally a comparison of the organisation of chromosomes in the MAX and MMX genomes, which differ primarily by the type of X chromosome, revealed that in a number of cases pairs of chromosomes are arranged very differently with respect to each other. The distribution of chromosomes on the hollow spindle was also analysed to investigate whether a specific spatial ordering of chromosomes exists within these Moreton genomes based on the association of pairs of short arms and pairs of long arms of most similar length (the Bennett model). The twelve chromosomes in both genomes were uniquely ordered in a single chain. However, because of computing limitations, only the ordered arrangement of chromosomes 1–10 was investigated. An analysis of 48 cells in the MMX and 38 cells in the MAX genomes showed that the predicted order in the ten chromosome sub-set in each genome did not rank in the top 20% of the 181,440 possible orders. This suggests that, although there is a good evidence that some non-homologous chromosomes may be associated non-randomly at metaphase in these genomes, they do not appear to show a specific, ordered arrangement as predicted by the Bennett model. The significance of the observed non-random organisation of chromosomes in the MMX and MAX genomes is discussed in relation to the generation of novel chromosome rearrangements in Moreton x Torresian F1 hybrids and the evolution of the Moreton and Torresian genomes.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 17 (1982), S. 3281-3287 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Antiferromagnetic domain boundaries in single-crystal NiO specimens have been examined by transmission electron microscopy. The domain boundaries were found to move through the matrix as a result of beam-induced thermal stresses. Movement of the boundaries was restricted by dislocations. Some evidence is given to show that domain boundaries may serve as nucleation sites for the reduced species in gaseous reduction of NiO. The presence of vacancy loops in nickel oxide has been established.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Plant systematics and evolution 137 (1981), S. 221-222 
    ISSN: 1615-6110
    Keywords: Posidoniaceae ; Posidonia ; Chromosome Numbers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The five species ofPosidonia occuring in Western Australia all have a diploid chromosome number of 20.
    Type of Medium: Electronic Resource
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  • 7
    Publication Date: 1984-11-01
    Print ISSN: 0009-5915
    Electronic ISSN: 1432-0886
    Topics: Biology , Medicine
    Published by Springer
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  • 8
    Publication Date: 1982-11-01
    Print ISSN: 0009-5915
    Electronic ISSN: 1432-0886
    Topics: Biology , Medicine
    Published by Springer
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  • 9
    Publication Date: 1982-11-01
    Print ISSN: 0009-5915
    Electronic ISSN: 1432-0886
    Topics: Biology , Medicine
    Published by Springer
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  • 10
    Publication Date: 1985-12-01
    Print ISSN: 0018-067X
    Electronic ISSN: 1365-2540
    Topics: Biology
    Published by Springer Nature
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