scholarly journals Chromosome breakage by pairs of closely linked transposable elements of the Ac-Ds family in maize.

Genetics ◽  
1991 ◽  
Vol 129 (3) ◽  
pp. 855-862 ◽  
Author(s):  
H K Dooner ◽  
A Belachew
Keyword(s):  
Transposable Elements ◽  
Chromosomal Rearrangements ◽  
Chromosome Breakage ◽  
Endosperm Development ◽  
Strong Tendency ◽  
Chromosome Breaks ◽  
Chromosome Breaking ◽  
Ac Transposition

Abstract Chromosome breaks and hence chromosomal rearrangements often occur in maize stocks harboring transposable elements (TEs), yet it is not clear what types of TE structures promote breakage. We have shown previously that chromosomes containing a complex transposon structure consisting of an Ac (Activator) element closely linked in direct orientation to a terminally deleted or fractured Ac (fAc) element have a strong tendency to break during endosperm development. Here we show that pairs of closely linked transposons with intact ends, either two Ac elements--a common product of Ac transposition--or an Ac and a Ds (Dissociation) element, can constitute chromosome-breaking structures, and that the frequency of breakage is inversely related to intertransposon distance. Similar structures may also be implicated in chromosome breaks in other eukaryotic TE systems known to produce chromosomal rearrangements. The present findings are discussed in light of a model of chromosome breakage that is based on the transposition of a partially replicated macrotransposon delimited by the outside ends of the two linked TEs.

Further observations on the nature of radiation-induced chromosomal interchanges recovered from Drosophila sperm

Genome ◽  
1989 ◽  
Vol 32 (5) ◽  
pp. 847-855 ◽  
Author(s):  
Daniel F. Eberl ◽  
Arthur J. Hilliker ◽  
Cecil B. Sharp ◽  
Silvija N. Trusis-Coulter
Keyword(s):  
Drosophila Melanogaster ◽  
Chromosomal Rearrangements ◽  
Strong Tendency ◽  
Chromosome 3 ◽  
Chromosome 2 ◽  
Mitotic Metaphase ◽  
Genetic Approach ◽  
Intercalary Heterochromatin ◽  
Chromosome Breaks ◽  
Radiation Induced

The induction and analysis of numerous translocations (identified genetically and characterized cytologically) between chromosomes 2 and 3 of Drosophila melanogaster have allowed us to reexamine three issues concerning the nature of radiation-induced interchanges in spermatozoa. First, our results support the idea that, relative to their mitotic metaphase length, all major chromosomal regions are similar in their breakability, whether euchromatic (proximal or distal) or heterochromatic. Second, analysis of all our reciprocal exchanges between the two chromosomes shows a statistically significant dependence of the position of the chromosome 2 breakpoint on that of the chromosome 3 breakpoint. Thirdly, our combined cytological and genetic approach strengthens the results of previous analyses, which suggested a strong tendency for chromosomal interchanges to be of the reciprocal type in multiple-break rearrangements. This indicates that if radiation induces chromosome breaks, then the resulting broken ends tend to rejoin in pairs rather than independently.Key words: Drosophila melanogaster, radiation mutagenesis, chromosomal rearrangements, heterochromatin, intercalary heterochromatin.

scholarly journals Gametocidal Genes Induce Chromosome Breakage in the Interphase Prior to the First Mitotic Cell Division of the Male Gametophyte in Wheat

Genetics ◽  
1998 ◽  
Vol 149 (2) ◽  
pp. 1115-1124 ◽  
Author(s):  
Shuhei Nasuda ◽  
Bernd Friebe ◽  
Bikram S Gill
Keyword(s):  
Cell Cycle ◽  
Male Gametophyte ◽  
Chromosomal Rearrangements ◽  
Low Frequency ◽  
Chromosome Breakage ◽  
Mitotic Cell ◽  
Aegilops Speltoides ◽  
Chromosome Breaks ◽  
Chromosome Fragments ◽  
Chromosome Bridges

Abstract Male gametogenesis was cytologically analyzed in wheat lines homozygous or hemizygous for gametocidal (Gc) factors with different modes of action. The first and second meiotic divisions in all lines were cytologically normal. The postmeiotic mitoses were normal in the homozygous lines; however, chromosome fragments and bridges were observed in the mitoses of the hemizygous lines. The morphology of the chromosome fragments suggests that the Gc genes induce chromosome breaks in the G1 phase prior to DNA synthesis of the first postmeiotic mitosis. The age of an anther was correlated with the frequency of aberrant second mitosis. Younger anthers contained a higher number of pollen undergoing normal second mitosis. This observation suggests that the arresting of the cell cycle occurs as the result of chromosome breaks during the first mitosis. Because chromosome bridges were more frequent than fragments in the second mitosis, breakage-fusion-bridge cycles possibly occurred during gametogenesis, which led to further chromosomal rearrangements. The Gc factors located on chromosomes 2S of Aegilops speltoides and 4Ssh of Ae. sharonensis induce severe chromosome breakage in pollen lacking them. However, the Gc factor on telosome 2CcL of Ae. cylindrica only induced chromosome breaks at a low frequency. The observed partial fertility of Gc lines is presumably due to cell cycle arrest and the competition among gametes with and without chromosome breakage.

scholarly journals Chromosome breakage undetectable in active Mu lines of maize.

Genetics ◽  
1989 ◽  
Vol 122 (1) ◽  
pp. 205-209
Author(s):  
L J Rowland ◽  
D S Robertson ◽  
J Strommer
Keyword(s):  
Transposable Elements ◽  
Low Frequency ◽  
Chromosome Breakage ◽  
Very Low Frequency ◽  
Induced Mutants ◽  
Simultaneous Loss

Abstract We have used a set of Mutator-induced mutants of Bz1 to test whether members of the Mutator (Mu) family of maize transposable elements produce broken chromosomes. From our inability to demonstrate the simultaneous loss of two dominant endosperm markers distal to Mu insertions at Bz1 we conclude that either Mu, unlike many elements of the Ds family, does not induce such breaks, or it does so at a very low frequency.

scholarly journals Transposable Elements and Teleost Migratory Behaviour

2021 ◽  
Vol 22 (2) ◽  
pp. 602
Author(s):  
Elisa Carotti ◽  
Federica Carducci ◽  
Adriana Canapa ◽  
Marco Barucca ◽  
Samuele Greco ◽  
...  
Keyword(s):  
Transposable Elements ◽  
Environmental Changes ◽  
Chromosomal Rearrangements ◽  
Quantitative Difference ◽  
Regulatory Elements ◽  
Phylogenetic Position ◽  
Migratory Behaviour ◽  
Relative Contribution ◽  
Migratory Routes ◽  
Eukaryotic Genomes

Transposable elements (TEs) represent a considerable fraction of eukaryotic genomes, thereby contributing to genome size, chromosomal rearrangements, and to the generation of new coding genes or regulatory elements. An increasing number of works have reported a link between the genomic abundance of TEs and the adaptation to specific environmental conditions. Diadromy represents a fascinating feature of fish, protagonists of migratory routes between marine and freshwater for reproduction. In this work, we investigated the genomes of 24 fish species, including 15 teleosts with a migratory behaviour. The expected higher relative abundance of DNA transposons in ray-finned fish compared with the other fish groups was not confirmed by the analysis of the dataset considered. The relative contribution of different TE types in migratory ray-finned species did not show clear differences between oceanodromous and potamodromous fish. On the contrary, a remarkable relationship between migratory behaviour and the quantitative difference reported for short interspersed nuclear (retro)elements (SINEs) emerged from the comparison between anadromous and catadromous species, independently from their phylogenetic position. This aspect is likely due to the substantial environmental changes faced by diadromous species during their migratory routes.

scholarly journals Cytogenomics Unveil Possible Transposable Elements Driving Rearrangements in Chromosomes 2 and 4 of Solea senegalensis

2021 ◽  
Vol 22 (4) ◽  
pp. 1614
Author(s):  
María Esther Rodríguez ◽  
Ismael Cross ◽  
Alberto Arias-Pérez ◽  
Silvia Portela-Bens ◽  
Manuel Alejandro Merlo ◽  
...  
Keyword(s):  
Transposable Elements ◽  
Fish Species ◽  
Gasterosteus Aculeatus ◽  
Sparus Aurata ◽  
Chromosomal Rearrangements ◽  
Scophthalmus Maximus ◽  
Cynoglossus Semilaevis ◽  
Solea Senegalensis ◽  
Reference Species ◽  
Artificial Chromosomes

Cytogenomics, the integration of cytogenetic and genomic data, has been used here to reconstruct the evolution of chromosomes 2 and 4 of Solea senegalensis. S. senegalensis is a flat fish with a karyotype comprising 2n = 42 chromosomes: 6 metacentric + 4 submetacentric + 8 subtelocentric + 24 telocentric. The Fluorescence in situ Hybridization with Bacterial Artificial Chromosomes (FISH-BAC) technique was applied to locate BACs in these chromosomes (11 and 10 BACs in chromosomes 2 and 4, respectively) and to generate integrated maps. Synteny analysis, taking eight reference fish species (Cynoglossus semilaevis, Scophthalmus maximus, Sparus aurata, Gasterosteus aculeatus, Xiphophorus maculatus, Oryzias latipes, Danio rerio, and Lepisosteus oculatus) for comparison, showed that the BACs of these two chromosomes of S. senegalensis were mainly distributed in two principal chromosomes in the reference species. Transposable Elements (TE) analysis showed significant differences between the two chromosomes, in terms of number of loci per Mb and coverage, and the class of TE (I or II) present. Analysis of TE divergence in chromosomes 2 and 4 compared to their syntenic regions in four reference fish species (C. semilaevis, S. maximus, O. latipes, and D. rerio) revealed differences in their age of activity compared with those species but less notable differences between the two chromosomes. Differences were also observed in peaks of divergence and coverage of TE families for all reference species even in those close to S. senegalensis, like S. maximus and C. semilaevis. Considered together, chromosomes 2 and 4 have evolved by Robertsonian fusions, pericentric inversions, and other chromosomal rearrangements mediated by TEs.

scholarly journals Spontaneous Activation of Quiescent Uq Transposable Elements during Endosperm Development in Zea Mays.

Genetics ◽  
1988 ◽  
Vol 119 (2) ◽  
pp. 457-464
Author(s):  
Y B Pan ◽  
P A Peterson
Keyword(s):  
Transposable Elements ◽  
Normal Growth ◽  
Growth Conditions ◽  
Inbred Lines ◽  
Endosperm Development ◽  
Maize Breeding ◽  
Breeding Lines ◽  
Element System ◽  
Aleurone Tissue ◽  
Sufficient Stimulus

Abstract This study addresses the question of the activation of quiescent transposable elements in maize breeding lines. The a-ruq reporter allele of the Uq transposable element system expresses Uq activity (spots or sectors of spots in otherwise colorless aleurone tissue) when exposed to various genotypes of assorted maize inbred lines lacking any active Uq element. This activation of quiescent Uq elements occurs randomly during the growth of the endosperm. It is concluded that there are components in the genome that enhance the rare activation of quiescent Uq elements. Further, it seems that this activation occurs in the absence of any stress-inducing treatment, but that normal growth conditions provide sufficient stimulus for such activation.

scholarly journals How Barbara McClintock discovered transposable elements in maize

2012 ◽  
Vol 10 (4) ◽  
pp. 3-13
Author(s):  
Keyword(s):  
Transposable Elements ◽  
Chromosomal Location ◽  
Chromosome Breakage ◽  
Dna Transposons ◽  
Barbara Mcclintock ◽  
Controlling Elements ◽  
Earthquake Event ◽  
Maize Kernels ◽  
The Relationship

The paper describes the early part of Barbara McClintock`s work on DNA transposons in maize, in which she discovered the Ac-Ds family of mobile "controlling elements". An account is first given of the cytology of the system that was used to generate intact chromosomes having "sticky" (broken) ends. Cytogenetical aspects of the chromatid and chromosome breakage-fusion-bridge cycles, deriving from breakage, are then described, which leads on to the way in which variegation in phenotypes of the maize kernels could be "read" in terms of chromosome breakage. The "genetic earthquake" event of 1944, triggered by introducing broken chromosomes into a zygote from both parents, lead to the discovery of Ds and Ac. Finding mobility of Ds from one chromosomal location to another was pure serendipity: the transposition showed itself while experiments were being undertaken to accurately map Ds. A similar chance observation revealed transposition of Ac as well, and then the relationship between the two elements was elucidated in terms of their autonomous and non-autonomous nature.

Riyadh Chromosome Breakage Syndrome: Mental Retardation With Depigmentation of the Skin and Hair

1992 ◽  
Vol 7 (1_suppl) ◽  
pp. S79-S82 ◽  
Author(s):  
Pinar T. Ozand ◽  
Manjula Waghray ◽  
Jay D. Cook ◽  
Kirtikant Sheth ◽  
Generoso G. Gascon
Keyword(s):  
Mental Retardation ◽  
Sister Chromatid ◽  
Chromosome Breakage ◽  
Hair Color ◽  
Γ Irradiation ◽  
Exchange Frequency ◽  
Chromosome Breaks ◽  
Chromosome Breakage Syndrome ◽  
Sister Chromatid Exchange Frequency ◽  
Spontaneous Chromosome

A 20-month-old infant with "silvery-blond" hair color, widespread confettilike depigmentation of the skin, and mental retardation was found to have, in lymphocytes and fibroblast cultures, increased spontaneous chromosome breaks and breaks induced by both mitomycin and γ-irradiation. The sister chromatid exchange frequency was normal. This child probably represents a new chromosome breakage syndrome. (J Child Neurol 1992;7(Suppl):S79-S82.)

MUTAGENESIS IN CAENORHABDITIS ELEGANS. II. A SPECTRUM OF MUTATIONAL EVENTS INDUCED WITH 1500 R OF γ-RADIATION

Genetics ◽  
1985 ◽  
Vol 109 (3) ◽  
pp. 493-511
Author(s):  
Raja E Rosenbluth ◽  
Cheryl Cuddeford ◽  
David L Baillie
Keyword(s):  
Dose Response ◽  
Response Curve ◽  
Chromosomal Rearrangements ◽  
Γ Radiation ◽  
Recessive Lethal ◽  
C Elegans ◽  
Chromosome Breaks ◽  
Additional Chromosome ◽  
Γ Ray ◽  
Do So

ABSTRACT We previously established a γ-ray dose-response curve for recessive lethal events (lethals) captured over the eT1 balancer. In this paper we analyze the nature of lethal events produced, with a frequency of 0.04 per eT1 region, at a dose of 1500 r. To do so, we developed a protocol that, in the absence of cytogenetics, allows balanced lethals to be analyzed for associated chromosomal rearrangements. A set of 35 lethal strains was chosen for the analysis. Although the dosage was relatively low, a large number of multiple-break events were observed. The fraction of lethals associated with rearrangements was found to be 0.76. Currently most X- and γ-ray dosages used for mutagenesis in C. elegans are 6000-8000 r. From our data we conservatively estimated that 43% of rearrangements induced with 8000 r would be accompanied by additional chromosome breaks in the genome. With 1500 r the value was 5%.—The 35 lethals studied were derived from 875 screened F1's. Among these lethals there were (1) at least two unc-36 duplications, (2) at least four translocations, (3) at least six deficiencies of chromosome V (these delete about 90% of the unc-60 to unc-42 region) and (4) several unanalyzed rearrangements. Thus, it is possible to recover desired rearrangements at reasonable rates with a dose of only 1500 r.—We suggest that the levels of ionizing radiation employed in most published C. elegans studies are excessive and efforts should be made to use reduced levels in the future.

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