scholarly journals THE RELATION BETWEEN DNA SYNTHESIS AND CHROMOSOME STRUCTURE AS RESOLVED BY X-RAY DAMAGE

1963 ◽  
Vol 18 (3) ◽  
pp. 525-540 ◽  
Author(s):  
H. J. Evans ◽  
J. R. K. Savage
Keyword(s):  
Tritiated Thymidine ◽  
Root Tip ◽  
X Rays ◽  
Type B ◽  
Physical Separation ◽  
X Irradiation ◽  
Tip Cells ◽  
Root Tip Cells ◽  
Chromosome Regions ◽  
In Cells

Vicia faba root tip cells were treated for short periods with tritiated thymidine, either immediately before or after exposure of roots to x-rays, and autoradiograph preparations were analysed in an attempt to test the hypothesis that chromatid type (B') aberrations are induced only in those chromosome regions that have synthesized DNA prior to x-irradiation, whereas chromosome type (B'') aberrations are induced only in unduplicated chromosome regions. Studying the relation between presence or absence of label at loci involved in aberrations, in cells irradiated at different development stages, and the pattern of labelling in cells carrying both types of aberration leads to the conclusion that B'' aberrations are induced only in unreplicated chromosome regions. Following replication, only B' aberrations are induced, but these aberrations are also induced in chromosome regions preparing to incorporate DNA. It is suggested that the doubled response of the chromosome to x-rays prior to DNA incorporation might reflect a physical separation of replicating units prior to replication. The aberration yields in damaged cells which were irradiated in G1 S, and early G2 were in the ratio of 1.0:2.0:3.2. The data indicate that the increased yield of B' in early G2 relative to S cells may be a consequence of changes in the spatial distribution of the chromosomes within the nucleus.

scholarly journals The Effect of Respiratory Inhibitors and Chelating Agents on the Frequencies of Chromosomal Aberrations Produced by X-Rays in Vicia

1959 ◽  
Vol 5 (3) ◽  
pp. 479-490 ◽  
Author(s):  
B. A. Kihlman
Keyword(s):  
Chromosomal Aberrations ◽  
Potassium Cyanide ◽  
Close Correlation ◽  
Inhibitory Effect ◽  
Pure Oxygen ◽  
Root Tip ◽  
X Rays ◽  
Low Oxygen ◽  
Tip Cells ◽  
Root Tip Cells

Nitrosophenylhydroxylamine-ammonium (cupferron), potassium cyanide, sodium azide, ethylenediaminetetraacetate (EDTA), α,α'-dipyridyl, and o-phenanthroline were tested (1) for their ability to enhance the frequencies of chromosomal aberrations produced by x-rays in the root tip cells of the broad bean, Vicia faba, and (2) for their ability to inhibit oxygen consumption of excised roots of the same plant. In all cases a close correlation was found between the inhibitory effect on respiration and the enhancement of the sensitivity to x-rays at low oxygen pressures. EDTA, dipyridyl, and o-phenanthroline did not affect respiration to any greater extent, and they were without influence on the radiosensitivity. Cyanide, azide, and cupferron, which strongly inhibited respiration, also increased the frequencies of chromosome aberrations produced by x-rays at low oxygen pressures. The relation between oxygen concentration and radiosensitivity was determined both in the presence and the absence of the respiratory inhibitor cupferron. When cupferron was present, the radiosensitivity was influenced by oxygen concentrations 30 times lower than those effective in the absence of the inhibitor. In an atmosphere of pure oxygen, an increase of radiosensitivity of about 20 per cent was obtained with cupferron, EDTA, and potassium cyanide.

REDUCTION OF CHROMOSOME NUMBER IN ROOT TIP CELLS OF MEDICAGO

1974 ◽  
Vol 16 (1) ◽  
pp. 219-227 ◽  
Author(s):  
R. S. Sadasivaiah ◽  
K. Lesins
Keyword(s):  
Chromosome Number ◽  
Ploidy Level ◽  
Chromosome Numbers ◽  
Plant Evolution ◽  
Root Tip ◽  
Aneuploid Chromosome ◽  
Tip Cells ◽  
Root Tip Cells ◽  
In Cells

Cytological studies on progenies obtained from intercrosses between colchicine-induced octoploid (2n = 8x = 64) plants of alfalfa showed normal, haploid and aneuploid chromosome numbers in cells of the same root tip. Critical observations on cells at different divisional stages revealed the occurrence of meiosis-like mitotic divisions, resulting in a reduction of chromosome number. The frequency of cells showing reductional divisions appeared to vary with the ploidy level of the material. The possible significance of chromosome reduction in plant evolution is indicated.

Sunlight decreased genotoxicity of azadirachtin on root tip cells of Allium cepa and Eucrosia bicolor

2010 ◽  
Vol 73 (5) ◽  
pp. 949-954 ◽  
Author(s):  
W. Kwankua ◽  
S. Sengsai ◽  
C. Kuleung ◽  
N. Euawong
Keyword(s):  
Allium Cepa ◽  
Root Tip ◽  
Tip Cells ◽  
Root Tip Cells

Salt Stress-induced Programmed Cell Death in Rice Root Tip Cells

2007 ◽  
Vol 49 (4) ◽  
pp. 481-486 ◽  
Author(s):  
Jian-You Li ◽  
Ai-Liang Jiang ◽  
Wei Zhang
Keyword(s):  
Cell Death ◽  
Salt Stress ◽  
Programmed Cell Death ◽  
Rice Root ◽  
Root Tip ◽  
Tip Cells ◽  
Root Tip Cells

Cytological evidence bearing on the origin of the B genome in polyploid wheats

Genome ◽  
1988 ◽  
Vol 30 (1) ◽  
pp. 36-43 ◽  
Author(s):  
K. Kerby ◽  
J. Kuspira
Keyword(s):  
Dna Hybridization ◽  
Triticum Turgidum ◽  
Root Tip ◽  
Cytological Evidence ◽  
B Genome ◽  
Genome Donor ◽  
The One ◽  
Genome Donors ◽  
Tip Cells ◽  
Root Tip Cells

To help elucidate the origin of the B genome in polyploid wheats, karyotypes of Triticum turgidum, Triticum monoccum, and all six purported B genome donors were compared. The analysis utilized a common cytological procedure that employed the most advanced equipment for the measurement of chromosome lengths at metaphase in root tip cells. A comparison of the karyotypes of T. turgidum and T. monococcum permitted the identification of B genome chromosomes of T. turgidum. These consist of two SAT pairs, one ST pair, three SM pairs, and one M pair of homologues. Comparisons of the chromosomes of the B genome of T. turgidum with the karyotypes of the six putative B genome donors showed that only the karyotype of Aegilops searsii was similar to the one deduced for the donor of the B genome in T. turgidum, suggesting that Ae. searsii is, therefore, the most likely donor of the B genome to the polyploid wheats. Support for this conclusion has been derived from geographic, DNA-hybridization, karyotype, morphological, and protein data reported since 1977. Reasons why the B genome donor has not been unequivocally identified are discussed.Key words: phylogeny, karyotypes, Triticum turgidum, Triticum monococcum, B genome, B genome donors.

scholarly journals Squash Preparations of Living Root-Tip Cells

Nature ◽  
1949 ◽  
Vol 164 (4178) ◽  
pp. 930-930 ◽  
Author(s):  
J. CHAYEN
Keyword(s):  
Root Tip ◽  
Living Root ◽  
Tip Cells ◽  
Root Tip Cells
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