Elimination of X-Ray Induced Aberrant Chromosomes in the Root Meristems of Two-Rowed Barley

Ikushima, Takaji; Ichikawa, Sadao

doi:10.1266/jjg.42.271

Cited by 7 publications

(3 citation statements)

References 21 publications

(19 reference statements)

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“…Dicentric chromosomes are produced through chromosomal exchanges occurred between two different breaks of chromosomes (Ichikawa, 1981b). Dicentric bridge is formed at anaphase when two centromeres of a dicentric chromosome moved toward opposite poles, and the probability of forming bridge at anaphase for a dicentric chromosome is 50% (Ikushima and Ichikawa, 1967). There are two types of bridges, i.e., of chromosome and chromatid types resulting from two breaks and an exchange before DNA replication (occurred at the G 1 period) and those after DNA replication (occurred during the S to G 2 periods), respectively (Ichikawa, 1981b).…”

Section: Discussionmentioning

confidence: 99%

Dicentric chromosome bridges in root tips and micronuclei in pollen tetrads induced by X rays and maleic hydrazide in Tradescantia clone BNL 4430.

Xiao

Ichikawa

1997

Genes Genet. Syst.

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Inductions of dicentric chromosome bridges in root-tip cells and of micronuclei in pollen tetrads by X rays and maleic hydrazide (MH) were studied in Tradescantia clone BNL 4430, in order to compare the accuracies of these endpoints for mutagenicity testings with that of somatic pink mutations in the stamen hairs of the same clone, the most accurate endpoint established in higher plant testers. The frequency of dicentric bridges in root-tip cells increased with X-ray doses with a slope of 1.249 on a log-log graph, the slope value being unexpectedly small (much smaller than the theoretical value of 2 for two-break events). The dose-response curve on a log-log graph for MH-induced dicentric bridges had a somewhat smaller slope of 1.188, and the bridges observed were predominantly of chromatid type, reflecting the nature of MH acting at the S period of cell cycle. As for X-ray-and MH-induced micronuclei in pollen tetrads, on the other hand, the dose-response curves could not be determined, excepting that for X-ray-induced micronuclei in pollen tetrads at earlier stage. Namely, the data obtained from pollen tetrads at later stage were not consistent with X-ray and MH doses, and those from pollen tetrads at earlier stage were also inconsistent with MH doses. These results were contrary to our expectation that the frequency of micronuclei would be more reliable in pollen tetrads at later stage than in those at earlier stage at least in clone BNL 4430, a hybrid clone. The micronucleus assay in pollen tetrads was also found to be unsuited for determining the effects of MH. Therefore, the assay of somatic mutations in Tradescantia stamen hairs is concluded to be the most accurate and most reliable mutagenicity test system with a high degree of reappearance.

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Section: Discussionmentioning

confidence: 99%

Dicentric chromosome bridges in root tips and micronuclei in pollen tetrads induced by X rays and maleic hydrazide in Tradescantia clone BNL 4430.

Xiao

Ichikawa

1997

Genes Genet. Syst.

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“…During that prolonged fixation time, therefore, cells with fragment and lagging type aberrations may have been eliminated from the meristem prior to the bridges. However, this explanation for illustrating the discrepancy of the most frequent aberration type appears inappropriate, since Ikushima and Ichikawa [24] demonstrated that the decreasing rates of acentrics and dicentrics were the same during 2-3 cell divisions after x-ray-irradiation at the barley root meristem. It is more likely that the discrepancy could be due to a different distribution and/or kind of DNA damage produced in a different physiological status.…”

Section: Spectrum Of Chromosome Aberrations Induced By Carbon Ions Ormentioning

confidence: 99%

Effect of fractionated exposure to carbon ions on the frequency of chromosome aberrations in tobacco root cells

Shimono

Shikazono²,

Inoue

et al. 2001

Radiation and Environmental Biophysics

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The induction of chromosome aberrations in tobacco root tip cells was measured after exposure to either 18 MeV/n carbon ions or 2 MeV electrons. The RBE value for acute exposure was found to be about 10. Splitting the dose into two fractions did not produce any significant effect on the yield of aberrations following carbon-ion exposure, whereas a clear decrease was observed after exposure to electrons thereby indicating an induction/activation of error-free repair after the first fraction. Moreover, this decrease appeared to be independent of the types of chromosome aberrations. On the other hand, it was suggested that the lack of any significant effect on the yield of aberrations is either due to a lack of error-free repair or to a less efficient damage repair after exposure to carbon ions.

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“…Both classical cytogenetic data (McClintock 1939) and recent studies of artificial chromosomes in Saccharomyces (Mann andDavis 1983, Koshland et al 1987) have shown that most dicentric chromosomes are mitoticaly unstable and they often form bridges and fragments during anaphase and are eventually lost. Dicentric bridge is formed when the two centromeres in each chromatid move towards opposite poles at anaphase, the region being stretched on the spindle (Mather and Stone 1933) and the probability of forming bridge at anaphase for a dicentric chromosome is 50% (Ikushima and Ichikawa 1967).…”

mentioning

confidence: 99%

Ultrastructural Evidence for the Flawless Transmission of a Dicentric Chromosome in Aloe vera. L.

Umesh

Ranganath²

2003

CYTOLOGIA

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Electronmicroscopic study has revealed a dicentric chromosome in the root tip cells of diploid Aloe vera, hitherto unreported in somatic cells of plants. The morphological aspects are described and the implications of such structural features of the dicentric are addressed in a functional perspective. It is also proposed that the presence of two functional kinetochores need not invariably lead to chromosome instability and loss.

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Elimination of X-Ray Induced Aberrant Chromosomes in the Root Meristems of Two-Rowed Barley

Cited by 7 publications

References 21 publications

Dicentric chromosome bridges in root tips and micronuclei in pollen tetrads induced by X rays and maleic hydrazide in Tradescantia clone BNL 4430.

Dicentric chromosome bridges in root tips and micronuclei in pollen tetrads induced by X rays and maleic hydrazide in Tradescantia clone BNL 4430.

Effect of fractionated exposure to carbon ions on the frequency of chromosome aberrations in tobacco root cells

Ultrastructural Evidence for the Flawless Transmission of a Dicentric Chromosome in Aloe vera. L.

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