Chromomeric organization of polytene chromosomes

Жимулев, И. Ф.; Belyaeva, E. S.

doi:10.1007/bf00056107

Cited by 10 publications

(2 citation statements)

References 34 publications

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“…These studies invariably find that there is an approximately equal number of genes and bands. However, some bands have been found that are multigenic and others have no discernible function (Berendes, 1970;Hochman, 1971;Lefevre, 1974;Young and Judd, 1978;Keppy and Welshons, 1980;Spierer and Spierer, 1983;Zhimulev and Belyaeva, 1991). The idea that each band may represent a single gene is further complicated by the occurrence of overlapping reading frames (Eveleth and Marsh, 1987) and coding regions that reside in the introns of other genes (Henikoff et al, 1986;Chen et al, 1987).…”

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confidence: 99%

A three-dimensional structural dissection of Drosophila polytene chromosomes.

Urata

Parmelee

Agard

et al. 1995

The Journal of Cell Biology

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Abstract. We have analyzed the three-dimensional structural details of Drosophila melanogaster polytene chromosome bands and interbands using three-dimensional light microscopy and a novel method of sample preparation that does not involve flattening or stretching the chromosomes. Bands have been visualized in unfixed chromosomes stained with the DNA specific dye 4,6-Diamidino-2-phenylindole (DAPI). Interbands have been visualized using fixed chromosomes that have been immunostained with an antibody to RNA polymerase II. Additionally, these structures have been analyzed using in situ hybridization with probes from specific genetic loci (Notch and white).Bands are seen to be composed of ~36 substructural features that measure 0.2-0.4 txm in diameter. We suggest that these substructural features are in fact longitudinal fibers made up of bundles of chromatids. Band shape can be a reproducible characteristic of a particular band and is dependent on the spatial relationship of these bundles, varying from bands with a uniform distribution of bundles to bands with a peripheral concentration of chromatin. Interbands are composed of bundles of chromatids of a similar size and number as those seen in the bands. The distribution of bundles is similar between a band and the neighboring interband, implying that there is a long range organization to the DNA that includes both the coding and the noncoding portions of genes. Finally, we note that the polytene chromosome has a circular shape when viewed in cross section, whether there are one or two homologs present. fundamental unsolved problem in biology is the organization of the eukaryotic genome in the interphase nucleus. During interphase, chromatin must be maintained in structures that allow site-specific regulated transcription and temporally controlled DNA replication. Normally, it is not possible to resolve individual chromosomes in the interphase nucleus by light microscopy. However, due to the process of polytenization, the giant salivary gland chromosomes of Drosophila melanogaster are large enough to visualize, thus providing an excellent model system for studying interphase processes. Polytenization occurs in nearly all larval tissues and is a result of a modified cell cycle, which alternates between S phase and G phase (Smith and Orr-Weaver, 1991). The polytene nuclei in salivary gland tissue can undergo up to 10 cycles of replication without intervening divisions. The unsegregated sister chromatids and homologs remain Y. Urata and S. J. Parmelee both contributed equally to the work presented herein.

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confidence: 99%

A three-dimensional structural dissection of Drosophila polytene chromosomes.

Urata

Parmelee

Agard

et al. 1995

The Journal of Cell Biology

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“…The chromosomes of multicellular animals have a regular and inheritable physical organization. This was first recognized in studies on the lampbrush chromosomes in amphibian oocytes and the polytene chromosomes of insects (Callan, 1963;Nora et al, 2020;Zhimulev and Belyaeva, 1991;Zhimulev et al, 1983). Subsequent research has shown that the architectural features inferred from analysis of lampbrush and polytene chromosomes are present in chromosomes throughout much of the animal kingdom.…”

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confidence: 93%

Chromosome Structure I: Loop extrusion or boundary:boundary pairing?

Bing,

Ke,

Fujioka

et al. 2023

Preprint

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Two different models have been proposed to explain how the endpoints of chromatin looped domains (“TADs”) in eukaryotic chromosomes are determined. In the first, a cohesin complex extrudes a loop until it encounters a boundary element roadblock, generating a stem-loop (and an unanchored loop). In this model, boundaries are functionally autonomous: they have an intrinsic ability to halt the movement of incoming cohesin complexes that is independent of the properties of neighboring boundaries. In the second, loops are generated by boundary:boundary pairing. In this model, boundaries are functionally non-autonomous, and their ability to form a loop depends upon how well they match with their neighbors. Moreover, unlike the loop-extrusion model, pairing interactions can generate both stem-loops and circle-loops. We have used a combination of MicroC to analyze how TADs are organized and experimental manipulations of theeven skippedTAD boundary,homie, to test the predictions of the “loop-extrusion” and the “boundary-pairing” models. Our findings are incompatible with the loop-extrusion model and instead suggest that endpoints of TADs in flies are determined by a mechanism in which boundary elements physically pair with their partners, either head-to-head, or head-to-tail, with varying degrees of specificity. How the partners find each other is not clear but is unlikely to require a loop extrusion mechanism.

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Organization of Genetic Material into Chromosomes

Shakoori

2017

Chromosome Structure and Aberrations

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Chromomeric organization of polytene chromosomes

Cited by 10 publications

References 34 publications

A three-dimensional structural dissection of Drosophila polytene chromosomes.

A three-dimensional structural dissection of Drosophila polytene chromosomes.

Chromosome Structure I: Loop extrusion or boundary:boundary pairing?

Organization of Genetic Material into Chromosomes

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