Cytological and Cytogenetical Studies on Normal and Interchange Allium Triquetrum

10.26686/wgtn.16958662 ◽

2021 ◽

Author(s):

◽

Geoffrey Keith Rickards

Keyword(s):

Chiasma Formation ◽

Reciprocal Translocations ◽

Chromosome Segments ◽

Present Understanding

<p>Interchanges (otherwise known as segmental chromosome interchanges or reciprocal translocations), involving exchanges of segments of nonhomologous chromosomes, have been studied extensively in plants. Probably the earliest observations were those of Gates (1903) on a ring of chromosomes at meiosis in Oenothera rubrinervis. Belling's reports of sterility in hybrids amongst certain velvet beans (Stizolobium) were later attributed to an interchange of chromosome segments (Belling, 1925). More clearly defined early cases were provided by McClintock's (1930) cytological demonstrations of interchanges in maize. Burnham's (1956) review indicates a sizable accumulation of data in plants. The researches in maize by Brink, McClintock and Burnham, and others, are by far the most extensive, and these data have contributed much to our present understanding of many cytological processes, particularly synapsis, chiasma formation and orientation phenomena.</p>

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RECIPROCAL TRANSLOCATIONS AND TRANSLOCATION DISOMICS OF ASPERGILLUS AND THEIR USE FOR GENETIC MAPPING

Genetics ◽

10.1093/genetics/79.1.7 ◽

1975 ◽

Vol 79 (1) ◽

pp. 7-30

Author(s):

Etta Käfer

Keyword(s):

Genetic Mapping ◽

Relative Position ◽

Normal Chromosome ◽

Large Chromosome ◽

Reciprocal Translocations ◽

New Techniques ◽

Chromosome Arm ◽

Chromosome Segments ◽

Heterozygous Translocation

ABSTRACT Two new techniques are described for genetic mapping of reciprocal translocations in A. nidulans, which can be used to locate centromeres and meiotically unlinked markers. They both make use of unbalanced disomics from heterozygous translocation crosses. These are mainly hyperhaploids of two classes: either typical-looking n + 1 with a normal chromosome in addition to a haploid set containing the translocation, or translocation disomics. When large chromosome segments are involved, such disomics, as well as stable aneuploids and duplication types, show characteristic phenotypes and can be classified visually. The first method maps translocation breaks qualitatively, since translocated markers can be identified when translocation disomics are analyzed for heterozygous markers. The second method measures meiotic linkage of any marker to the translocation breaks when allele ratios in the balanced haploid sectors of either or both classes of disomics are determined: linked markers show reciprocal deviations from 1:1—In addition, it can be shown that frequencies of nondisjunction and recovery of specific translocation disomics both depend on the relative position of the break within a chromosome arm. Such information can provide a rough estimate of the positions of breaks for a new translocation.—Using these techniques, as well as mitotic mapping in homo- and heterozygous translocation diploids, four reciprocal translocations were mapped. From these results, information on the sequence and orientation of most of the "meiotic fragments" of the current maps (groups III, VI, VII and VIII) was obtained, and the position of the centromeres of groups VI and VII were identified. Translocation disomics are also used to map meiotically unlinked single genes, e.g. oliA of group VII, to specify chromosome segments.

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CHIASMA STUDIES IN STRUCTURAL HYBRIDS. VIII. FURTHER EVIDENCES FOR CHIASMA FORMATION BY CROSSING-OVER IN RECIPROCAL TRANSLOCATIONS OF SCILLA SCILLOIDES

The Japanese Journal of Genetics ◽

10.1266/jjg.42.89 ◽

1967 ◽

Vol 42 (2) ◽

pp. 89-93 ◽

Cited By ~ 4

Author(s):

SHOZO NODA

Keyword(s):

Chiasma Formation ◽

Crossing Over ◽

Reciprocal Translocations ◽

Scilla Scilloides

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A strategy for detecting chromosome-specific rearrangements in rye

Genome ◽

10.1139/g97-060 ◽

1997 ◽

Vol 40 (4) ◽

pp. 451-457 ◽

Cited By ~ 6

Author(s):

E. Alvarez ◽

C. Alonso-Blanco ◽

R. García Suárez ◽

J. J. Ferreira ◽

A. Roca ◽

...

Keyword(s):

Structural Changes ◽

Equal Length ◽

Reciprocal Translocations ◽

X Ray ◽

C Banding ◽

Ring Chromosomes ◽

Chromosome 1R ◽

Chromosome Segments

To obtain translocations involving specific chromosomes in rye, a line in which chromosome 1R has large C-bands on its two telomeres but which lacks C-bands (or has very small ones) on the telomeres of the remaining chromosomes was used. About 6% of the plants produced using pollen from irradiated (1.2 krad (1 rad = 10 mGy)) spikes of this line possessed structural changes involving the labeled chromosome. These aberrations included translocations, ring chromosomes, isochromosomes, and telocentrics. It is concluded (i) that all nonlabeled chromosomes have the same probability of participating in reciprocal translocations with the labeled chromosome, 1R, and (ii) that most induced reciprocal translocations involved exchanges of chromosome segments of approximately equal length. The use of lines having the appropriate combination of telomeric C-bands improves the efficiency of obtaining reciprocal translocations involving specific chromosomes that could be used in the construction of detailed physical maps.Key words: Secale, translocations, C-banding, x-ray irradiation.

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A stably transmitted pair of translocated supernumerary chromosomes in maize

Genome ◽

10.1139/g95-072 ◽

1995 ◽

Vol 38 (3) ◽

pp. 558-565 ◽

Cited By ~ 1

Author(s):

Marjorie P. Maguire

Keyword(s):

Chiasma Formation ◽

B Chromosome ◽

Supernumerary Chromosome ◽

Chromosome Segment ◽

Crossing Over ◽

Preferential Pairing ◽

Supernumerary Chromosomes ◽

Unknown Source ◽

Chromosome Segments

A pair of stably transmitted supernumerary chromosomes of unknown source has been found in a maize stock carrying a desynaptic mutant. The presence of the supernumerary chromosome appears to be unrelated to the meiotic mutant, but is believed to have been derived from a translocated B chromosome contaminant. The supernumerary chromosomes carry a segment of a A chromosome in this stock where there appear to be two normal copies of each of the 10 A chromosomes. Thus, this A chromosome segment is present in quadruplicate. Surprisingly, a quadrivalent configuration is formed in most microsporocytes, which involves not only synapsis but also chiasma formation in the A chromosome segments involved in the quadrivalent. This represents a strong preferential pairing of supernumeraries with the normal A chromosome segments. Such nonrandom association and crossing over might provide information on the nature of early homologue alignment at meiosis.Key words: supernumerary chromosomes, modified B chromosome, BA translocation, preferential pairing and crossing over.

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Radiation Damage in Ceramics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055229 ◽

1982 ◽

Vol 40 ◽

pp. 600-603

Author(s):

T. E. Mitchell ◽

M. R. Pascucci ◽

R. A. Youngman

Keyword(s):

Radiation Damage ◽

Outer Space ◽

Point Of View ◽

Nuclear Waste Storage ◽

Waste Storage ◽

Storage Media ◽

Transmission Electron ◽

Fundamental Point ◽

Small Defect ◽

Present Understanding

1. Introduction. Studies of radiation damage in ceramics are of interest not only from a fundamental point of view but also because it is important to understand the behavior of ceramics in various practical radiation enyironments- fission and fusion reactors, nuclear waste storage media, ion-implantation devices, outer space, etc. A great deal of work has been done on the spectroscopy of point defects and small defect clusters in ceramics, but relatively little has been performed on defect agglomeration using transmission electron microscopy (TEM) in the same kind of detail that has been so successful in metals. This article will assess our present understanding of radiation damage in ceramics with illustrations using results obtained from the authors' work.

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Molecular Mechanism of Apoptosis Induction by Resveratrol, a Natural Cancer Chemopreventive Agent

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831.78.1.3 ◽

2008 ◽

Vol 78 (1) ◽

pp. 3-8 ◽

Cited By ~ 19

Author(s):

Fan ◽

Jiang ◽

Zhang ◽

Bai

Keyword(s):

Cancer Treatment ◽

Molecular Mechanism ◽

Apoptosis Induction ◽

Protective Agents ◽

Chemopreventive Agent ◽

Naturally Occurring ◽

Apoptosis Pathways ◽

Present Understanding

In efforts to identify naturally occurring compounds that act as protective agents, resveratrol, a phytoalexin existing in wine, has attracted much interest because of its diverse pharmacological characteristics. Considering that apoptosis induction is the most potent defense approach for cancer treatment, we have tried to summarize our present understanding of apoptosis induction by resveratrol based on the two major apoptosis pathways.

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