DISTRIBUTION OF HETEROCHROMATIN IN THE CHROMOSOMES OF HAPLOPAPPUS GRACILIS

1968 ◽  
Vol 10 (2) ◽  
pp. 433-443 ◽  
Author(s):  
Ira H. Ames ◽  
Jyotirmay Mitra
Keyword(s):  
Aqueous Solution ◽  
Chromosome Aberrations ◽  
Maleic Hydrazide ◽  
Cold Treatment ◽  
The Other ◽  
Root Tip ◽  
Metaphase Chromosomes ◽  
Haplopappus Gracilis ◽  
Tip Cells ◽  
Root Tip Cells

Several approaches were employed to study the distribution of heterochromatin in root tip chromosomes of Haplopappus gracilis. Cold treatment and pretreatment in an aqueous solution of 8-hydroxyquinoline revealed achromatic gaps in metaphase chromosomes. Cold treatment also permitted the demonstration of positive heteropycnosis in prophase chromosomes. Further support for the identification of heterochromatic segments was provided by a study of the localization of chromosome aberrations induced by maleic hydrazide and an analysis of the pattern of DNA synthesis in chromosomes of root tip cells. Seven of the ten regions that were preferentially broken by maleic hydrazide also reacted differentially to cold treatment or to pretreatment with 8-hydroxyquinoline. A good correlation was found between regions that completed DNA replication late in the DNA-synnhetic period and segments that were shown to be heterochromatic by the other techniques.

Detection of Chemically Induced Aneuploidy by the Vicia Faba Root Tip Assay

1988 ◽  
Vol 4 (2) ◽  
pp. 257-278 ◽  
Author(s):  
Shahbeg S. Sandhu ◽  
Georgia N. Acedo
Keyword(s):  
Vicia Faba ◽  
Lithium Chloride ◽  
Maleic Hydrazide ◽  
Assay System ◽  
Root Tip ◽  
Short Term ◽  
Promising Tool ◽  
Chemically Induced ◽  
Tip Cells ◽  
Root Tip Cells

Six chemicals selected for their ability to induce aneuploidy in short-term bioassays were tested for their aneuploidy-inducing potential in the Vicia faba root assay system. Para-fluorophenylalanine, griseofulvin, maleic hydrazide, lithium chloride, and cyclophosphamide all induced significant levels of hyperdiploidy in V. faba root tip cells. Lithium chloride and sodium azide were negative for hyperdiploidy induction. In addition to the numerical loss or gain in chromosome number, the chemicals induced other specific chromosomal effects, possibly indicating different mechanisms by which these chemicals bring about genomic imbalance. Judging from the lowest effective aneuploidy-inducing dose of each chemical, the V. faba root tip assay system appears to be a sensitive and promising tool for evaluating the potential of chemicals to induce aneuploidy.

scholarly journals INCORPORATION OF C14-LABELED MALEIC HYDRAZIDE INTO THE ROOT-TIP CELLS OF ALLIUM CERNUUM, VICIA FABA, AND TRADESCANTIA PALUDOSA

1961 ◽  
Vol 10 (4) ◽  
pp. 567-575 ◽  
Author(s):  
John J. Callaghan ◽  
Paul Grun
Keyword(s):  
Vicia Faba ◽  
Maleic Hydrazide ◽  
Root Tip ◽  
Nucleolar Localization ◽  
Root Tips ◽  
Tip Cells ◽  
Root Tip Cells ◽  
Tradescantia Paludosa

Allium cernuum, Vicia faba, and Tradescantia paludosa were treated by root immersion in maleic hydrazide (1 mM/liter) labeled with C14 (C14-MH) for 1 hour to determine the location within the cell to which MH moves during various periods of time after treatment. Root tips were fixed 24 hours, 48 hours, 72 hours, and 3 weeks after treatment. Autoradiographs of root tips squashed 24 to 72 hours after fixation showed that C14-MH was distributed throughout the nuclei and was particularly concentrated in the nucleoli. The nucleolar localization of the chemical was transitory, fixations made 3 weeks after treatment showing well labeled nuclei many of which completely lacked label in the nucleoli. The chromosomes seen in mitotic divisions of all three species had the same amount of label in euchromatic as heterochromatic areas. Since the chemical was not accumulated preferentially in heterochromatic areas, it seems likely that the reported specificity of MH for the breakage of heterochromatin can not be due to preferential heterochromatic incorporation.

CHROMOSOME ABERRATIONS PRODUCED BY 5-BROMODEOXYURIDINE WITH CONCURRENT EXPOSURE TO LONG WAVELENGTH UV IN ZEA MAYS ROOT TIP CELLS

1977 ◽  
Vol 19 (3) ◽  
pp. 447-459 ◽  
Author(s):  
R. S. Verma ◽  
J. E. Cummins ◽  
D. B. Walden
Keyword(s):  
Zea Mays ◽  
Chromosome Aberrations ◽  
Cesium Chloride ◽  
Root Tip ◽  
Chromosome Damage ◽  
Root Tips ◽  
Long Wavelength ◽  
Small Pool ◽  
Tip Cells ◽  
Root Tip Cells

The influence of bromodeoxyuridine (BrUrdR) on the pattern and level of chromosome damage in Zea mays L. root tip cells is described. In some experiments long wavelength ultraviolet light was employed to convert the bromodeoxyuridine in DNA to its photoproduct. BrUrdR treatment produced a marked decrease in the mitotic index and a high proportion of the mitotic cells bore chromosome damage. Following a BrUrdR treatment of 5 h the proportion of damaged cells increased from 20% to 60% during the 20 h following treatment; then the proportion decreased sharply to less than 20%. Root tips treated as above followed by an exposure to long wavelength ultraviolet radiation (UV) had a proportion of damaged cells (80% at 20 h) only slightly greater than those not exposed to UV up to 20 h after treatment. Unlike the unirradiated BrUrdR substituted root tips, the proportion of damaged cells remained high 25 h after treatment. Furthermore, the spectrum of chromosome aberrations differed between irradiated and unirradiated BrUrdR substituted cells. Root tips exposed to long wavelength UV alone showed some damage that was limited to a stage in the cell cycle of irradiated root tips. Analysis of the BrUrdR treated corn DNA by cesium chloride density centrifugation showed that BrUrdR substitution for thymidine in DNA was extensive. Further experiments demonstrated that a large BrUrdR pool was not carried into the rounds of replication following BrUrdR removal from the medium. Nevertheless a small pool of halogenated pyrimidine was observable after BrUrdR removal from the medium.

Ultrastructure of metaphase chromosomes and interphase nuclei

1994 ◽  
Vol 52 ◽  
pp. 346-347
Author(s):  
Philip S. Woods ◽  
Myron C. Ledbetter ◽  
Jack Van't Hof
Keyword(s):  
Vicia Faba ◽  
Freeze Substitution ◽  
Root Tip ◽  
Metaphase Chromosomes ◽  
Interphase Nuclei ◽  
Whole Mount ◽  
20 Nm ◽  
Relationship Of ◽  
Tip Cells ◽  
Root Tip Cells

Electron microscopy of whole-mount preparations of chromosomes and nuclei was greatly improved upon over earlier studies, when techniques were developed to expand the specimen and to preserve the expanded state during drying. When the earlier procedures were followed, the thick and dense chromosomes and nuclei always appeared nearly opaque to the electron beam and yielded little information regarding internal structure. With the newer techniques, it has been possible to study structure in detail deep within these specimens. The chromosomes of the plant Vicia faba are composed of a very long thin (5-20 nm) fiber which consists of about 38% DNA, with a presumed equal amount of histones; and a thicker 15-55 nm net-like component consisting of the remaining 24%, as nonhistones. Our interests concern determining the structural relationship of these components in chromosomes and nuclei of root-tip cells of this same plant.Fig. 1 shows a Vicia faba metaphase chromosome expanded with EDTA and processed by freeze-substitution. Inset, at the same magnification, shows an untreated similarly processed control chromosome.

MITOTIC CYCLES IN ROOT TIP CELLS OF TWO SPECIES OF TRILLIUM (LILIACEAE)

1970 ◽  
Vol 12 (4) ◽  
pp. 750-758 ◽  
Author(s):  
E. R. Boothroyd ◽  
Nancy MacDonald Mark
Keyword(s):  
Mitotic Cycle ◽  
The Other ◽  
Root Tip ◽  
Cycle Times ◽  
Autoradiographic Technique ◽  
Tip Cells ◽  
Root Tip Cells

There is a fourfold difference in the reported lengths of the mitotic cycles in Trillium. One report (29 hours at 23 °C for T. erectum) was based on the colchicine tag method, whereas the other (120 hours at 25 °C for T. grandiflorum) was based on the autoradiographic technique. In the present study both methods were used on both species. Experiments, carried out at 20 °C, gave minimum estimates of 104 hours and 84 hours respectively for T. grandiflorum and T. erectum, as determined by the colchicine method, and 92 hours and 80 hours by autoradiography. Both methods gave evidence of the existence of two or more populations of cells with different mitotic cycle times.

SPONTANEOUS CHROMOSOME ABERRATIONS IN MELANDRIUM

1968 ◽  
Vol 10 (1) ◽  
pp. 143-147 ◽  
Author(s):  
Hiran C. Choudhuri
Keyword(s):  
Chromosome Aberrations ◽  
Pollen Grains ◽  
Root Tip ◽  
Dicentric Chromosomes ◽  
Ring Chromosomes ◽  
Melandrium Album ◽  
Spontaneous Chromosome ◽  
First And Second Generation ◽  
Tip Cells ◽  
Root Tip Cells

Chromosome aberrations were observed in root tip cells of Melandrium album. These aberrations were generally in the form of dicentric chromosomes involving bridge formation, ring chromosomes, fragments and elimination of acentric fragments from daughter nuclei. All the aberrations varied from 19.6 to 10.7 per cent in the first and second generation seedlings respectively. The chromosome irregularities and abortion of pollen grains (4.0 to 5.0%) are presumably due to gene mutation which has been enhanced in aged seeds.

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