Chiasma frequency and the disjunction of interchange associations in rye

Rees, H.; Sun, S

doi:10.1007/bf00343177

Cited by 24 publications

(8 citation statements)

References 17 publications

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“…A multivalent attaining an alternate orientation has been attributed to a number of factors, e.g. (i) the presence of similar sized isobrachial chromosomes with distally located chiasmata; (ii) a reduction in chiasma frequency per interchanged complex (Rees and Sun 1965;John 1990); (iii) a strong selection favoring alternate orientation to produce fertile gametes and subsequently the enhanced seed set (Lawrence 1958(Lawrence , 1963; and (iv) short inter-centromeric length relative to spindle length (Rickards 1983). However, these factors, though expected to enhance alternate orientation, are not always sufficient to guarantee it (John 1990).…”

Section: Discussionmentioning

confidence: 99%

Variable multivalent orientations during diakinesis and metaphase I in microsporocytes ofTradescantia spathaceaSw.

Koul¹,

Nagpal²,

Kumar

2013

Caryologia

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Meiotic studies carried out on seven plants/clones of Tradescantia spathacea did not show the expected ring of 12 chromosomes in any of the 1765 cells studied at diakinesis (1202 cells) and metaphase I (563 cells). While at diakinesis the chromosomes resolved into chain configurations of all lengths ranging from one through 12 chromosomes, with the mean per cell being 2.47 ± 1.28, at metaphase I chains carrying up to 10 chromosomes were seen and the mean per cell was 4.18 ± 1.47. However, the larger chains were not the most frequent configurations observed at the two stages. Bivalents and univalents were the most frequent configurations observed in 38.68 and 43.92% cells at diakinesis and 63.94 and 57.72% cells at metaphase I, followed by chains of 10 (29.95% cells) and chains of three (51.50% cells) at the two stages, respectively. The larger chains, though visible at both the meiotic stages, varied significantly in the centromere orientation patterns. While at diakinesis they predominantly showed linear or indifferent orientation, at metaphase I 83.25% chains showed alternate orientation, with the rest showing linear and/or indifferent orientation. A high frequency of alternate orientation was observed in chains of three chromosomes (93.93%), followed by the chains of five and four, where 74.19 and 71.27% chains appeared in alternate orientation, respectively. In 4.97% cells with two chains of six chromosomes each, contrasting behavior was noticed in the two chains in respect of orientation. While one chain appeared zigzagged with alternate centromeres facing the same pole, the other chain invariably appeared in linear configuration. As a result of complex configurations at metaphase I and the high frequency of univalents, anaphase I segregation of chromosomes was highly irregular with 84% cells showing 1-3 lagging chromosomes. The average pollen viability determined for the seven clones studied was very low (17.87 ± 2.57%). The probable cause(s) of the different behaviors of the chain multiples at the two meiotic stages is discussed.

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Section: Discussionmentioning

confidence: 99%

Variable multivalent orientations during diakinesis and metaphase I in microsporocytes ofTradescantia spathaceaSw.

Koul¹,

Nagpal²,

Kumar

2013

Caryologia

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“…Once again, available data and hypotheses are contradictory (Rees & Sun, 1965;Sybenga, 1975;Rickards, 1977Rickards, , 1983Wise & Rickards, 1977;de Boer & van Beek, 1982;Diez & Puertas, 1984;Cabrero & Camacho, multiple configurations rearrangements in the 1985; Arana et a!., 1987;Parker, 1987;Bidau, 1990). According to the tension hypothesis, a given orientation is stable when forces exerted by spindle fibres upon a centromere are balanced against opposite forces that operate on a centromere connected to the first one (Sybenga, 1975;Rickards, 1983;Narasinga Rao & Sybenga, 1984;Sybenga & Rickards, 1987).…”

Section: Discussionmentioning

confidence: 99%

“…Despite the large number of works on these problems, only a few provide statistical evidence on the effects of chiasma frequency and position on multiple orientation (Rees & Sun, 1965;Diez & Puertas, 1984;Cabrero & Camacho, 1985;Arana et a!., 1987a, b;Cano & Santos, 1990), and, if statistical evidence exists, in general it reflects the relation between chiasma frequency and orientation. Most papers, however, suggest the existence of such a correlation and the relationship between chromosome change and chiasma change is well documented (Sybenga, 1975;Arana et al, 1982;Rickards, 1983;John, 1987;Parker, 1987;Bidau, 1990).…”

Section: Introductionmentioning

confidence: 99%

Proximal chiasmata induce non-disjunctional orientation of Robertsonian trivalents in a grasshopper

Mirol

Bidau

1992

Heredity

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The relationship between the symmetry of the meiotic configuration and the type of meiotic orientation (disjunctional and non-disjunctional) in Robertsonian trivalents of Dichroplus pratensis (Melanoplinae, Acrididae) was analysed. The results indicate, first, that neither chromosomal size nor the relation between the length of the chromosomes involved in each fusion are important factors for the determination of the orientation. Second, chiasmata localization, which in turn determines effective inter-centromeric distance, may be central. A high positive correlation between proximal chiasma frequency and non-disjunctional orientation at Prometaphase I and Metaphase I was found. These results are in agreement with the hypothesis that the shorter the inter-centromeric distance the greater is the probability that both centromeres migrate to the same pole. The importance of these results is also discussed in relation to the stability of the polymorphisms in this species.

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“…Table 1. Number of cells with one or two chiasmata in the involved chromosomes for 1/4, 3/4 and X/5 fusions in fused and unfused karyotypes Chromosome polymorphisms in natural populations are frequently associated with effects on chiasma frequency and distribution (Rees and Sun 1965, White 1973, Weissman 1976, Parker et al 1982, Hewitt 1979, Rickards 1983, Confalonieri 1988, Colombo 1989, Remis 1989, Bidau 1990). These effects usually improve meiotic segregation in structural heterozygotes, favouring the maintenance of such mutations in natural populations.…”

Section: Influence Of Spontaneous Fusions On Chiasma Conditionsmentioning

confidence: 99%

Spontaneous Centric Fusions Affecting Chiasma Conditions in Dichroplus elongatus (Orthoptera).

1996

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Chiasma frequency and the disjunction of interchange associations in rye

Cited by 24 publications

References 17 publications

Variable multivalent orientations during diakinesis and metaphase I in microsporocytes ofTradescantia spathaceaSw.

Variable multivalent orientations during diakinesis and metaphase I in microsporocytes ofTradescantia spathaceaSw.

Proximal chiasmata induce non-disjunctional orientation of Robertsonian trivalents in a grasshopper

Spontaneous Centric Fusions Affecting Chiasma Conditions in Dichroplus elongatus (Orthoptera).

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