polytene chromosome

• 多糸染色体

WordNet

1. a threadlike strand of DNA in the cell nucleus that carries the genes in a linear order; "humans have 22 chromosome pairs plus two sex chromosomes"

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1. 染色体

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/06/15 04:49:14」(JST)

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Polytene chromosomes in a Chironomus salivary gland cell

Polytene chromosome

Polytene chromosomes are over-sized chromosomes which have developed from standard chromosomes and are commonly found in the salivary glands of Drosophila melanogaster.Specialized cells undergo repeated rounds of DNA replication without cell division (endomitosis), to increase cell volume, forming a giant polytene chromosome. Polytene chromosomes form when multiple rounds of replication produce many sister chromatids that remain synapsed together.

Function

In addition to increasing the volume of the cells' nuclei and causing cell expansion, polytene cells may also have a metabolic advantage as multiple copies of genes permits a high level of gene expression. In Drosophila melanogaster, for example, the chromosomes of the larval salivary glands undergo many rounds of endoreduplication, to produce large amounts of glue before pupation. Another example, within the organism itself is the tandem duplication of various polytene bands located near the centromere of the X chromosome which results in the Bar phenotype of kidney-shaped eyes.

Structure

Polytene chromosomes have characteristic light and dark banding patterns that can be used to identify chromosomal rearrangements and deletions. Dark banding frequently corresponds to inactive chromatin, whereas light banding is usually found at areas with higher transcriptional activity. The banding patterns of the polytene chromosomes of Drosophila melanogaster were sketched in 1935 by Calvin B. Bridges, in such detail that his maps are still widely used today. The banding patterns of the chromosomes are especially helpful in research, as they provide an excellent visualization of transcriptionally active chromatin and general chromatin structure. For example, the polytene chromosomes in Drosophila have been used to support the theory of genomic equivalence, which states that all of the cells in the body maintain the same genome. Chromosome puffs are diffused uncoiled regions of the polytene chromosome that are sites of RNA transcription. A Balbiani ring is a large chromosome puff. Polytene chromosomes are about 200 µm in length. The chromonema of these chromosomes divide but do not separate. Therefore, they remain together to become large in size. Another form of chromosomal enlargement that provides for increased transcription is the lampbrush chromosome.

History

Polytene chromosomes were originally observed in the larval salivary glands of Chironomus midges by Balbiani in 1881, but the hereditary nature of these structures was not confirmed until they were studied in Drosophila melanogaster in the early 1930s by Emil Heitz and Hans Bauer. They are known to occur in secretory tissues of other dipteran insects such as the Malpighian tubules of Sciara and also in protists, plants, mammals, or in cells from other insects. Some of the largest polytene chromosomes described thus far (see scale bar in figure below) occur in larval salivary gland cells of the Chironomid genus Axarus.

Polytene chromosomes are also used to identify the species of Chironomid larvae that are notoriously difficult to identify. Each morphologically distinct group of larvae consists of a number of morphologically identical (sibling) species that can only be identified by rearing adult males or by cytogenetic analysis of the polytene chromosomes of the larvae. Karyotypes are used to confirm the presence of specific species and to study genetic diversity in species with a wide range.

References

Other References

• Baudisch W (1977). "Balbiani ring pattern and biochemical activities in the salivary gland of Acricotopus lucidus (Chironomidae)". Results Probl Cell Differ 8: 197–212. PMID 335467. 
• Bridges CB (1935). "Salivary chromosome maps with a key to the banding of the chromosomes of Drosophila melanogaster". J Heredity 26: 60–64. 
• Daneholt B (1992). "The transcribed template and the transcription loop in Balbiani rings". Cell Biol Int Rep 16 (8): 709–715. doi:10.1016/S0309-1651(05)80015-3. PMID 1446347. 
• Werle SF, E Klekowski and DG Smith (2004). "Inversion polymorphism in a Connecticut River Axarus species (Diptera: Chironomidae): biometric effects of a triple inversion heterozygote". Can. J. Zool. 82: 118–129. doi:10.1139/z03-227. 
• PAVAN, C. and BREUER, M. E. 1952. Polytene chromosomes in different tissues of Rhynchosciara. Journal of Heredity. vol. 63, p. 151-157.

• PAVAN, C. 1967. Chromosomal changes induced by infective agents Triangle. Sandoz J. Med. Sci. vol. 8, p. 42-48.

• PAVAN, C., BIESELE, J., RIESS, R. W. and WERTZ, A. V. 1971. XIII. Changes in the ultrastructure of Rhynchosciara cells infected by Microsporidia. Studies in Genetics. vol. VI, p. 7103.

• PAVAN, C., DA CUNHA, A. B. and MORSOLETTO, C. 1971. Virus-chromosome relationships in cells of Rhynchosciara (Diptera, Sciaridae). Caryologia. vol. 24, p. 371-389.

External links

• [1] (87A&C Heat-shock puffs)
• [2] (High resolution spreads)
• Phaseolus Polytene chromosomes (Plants)

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English Journal

• Proximity ligation assays of protein and RNA interactions in the male-specific lethal complex on Drosophila melanogaster polytene chromosomes.

• Lindehell H1, Kim M, Larsson J.
• Chromosoma.Chromosoma.2015 Sep;124(3):385-95. doi: 10.1007/s00412-015-0509-x. Epub 2015 Feb 19.
• In Drosophila, the male-specific lethal (MSL) complex specifically targets the male X chromosome and participates in a twofold increase in expression output leading to functional dosage compensation. The complex includes five proteins and two non-coding RNAs (ncRNAs). A number of additional associat
• PMID 25694028

• Cryptic biodiversity in the cytogenome of bird-biting blackflies in North Africa.

• Adler PH1, Cherairia M2, Arigue SF3, Samraoui B2,4, Belqat B5.
• Medical and veterinary entomology.Med Vet Entomol.2015 Sep;29(3):276-89. doi: 10.1111/mve.12115. Epub 2015 Mar 20.
• Bird-biting blackflies in the Simulium (Eusimulium) aureum group (Diptera: Simuliidae) are widespread vectors of Leucocytozoon and Trypanosoma parasites. The polytene chromosomes of 619 larvae of the three nominal members of the S. aureum group in North Africa were evaluated cytogenetically for cr
• PMID 25801314

• A standard photomap of ovarian nurse cell chromosomes in the European malaria vector Anopheles atroparvus.

• Artemov GN1, Sharakhova MV1,2, Naumenko AN2, Karagodin DA3, Baricheva EM3, Stegniy VN1, Sharakhov IV2.
• Medical and veterinary entomology.Med Vet Entomol.2015 Sep;29(3):230-7. doi: 10.1111/mve.12113. Epub 2015 Mar 17.
• Anopheles atroparvus (Diptera: Culicidae) is one of the main malaria vectors of the Maculipennis group in Europe. Cytogenetic analysis based on salivary gland chromosomes has been used in taxonomic and population genetic studies of mosquitoes from this group. However, a high-resolution cytogenetic m
• PMID 25776224

Japanese Journal

• The structural and molecular analysis of endoreduplicated nuclei in tomato (Solanum lycopersicum) fruit provides evidence for a ploidy-dependent increase in transcriptional activity

• , , [他], , , , , ,
• Plant Biotechnology 30(3), 301-307, 2013
• … We have developed a new method based on bacterial artificial chromosome fluorescent in situ hybridization (BAC-FISH) that allows the in situ determination of DNA ploidy levels of individual nuclei. … The use of the DNA FISH method demonstrated that endopolyploidy leads to the formation of polytene chromosomes, whereas the use of a RNA FISH method demonstrated that the rDNA transcription was increased during polyploidization. …
• NAID 130003362435

• 逆位と遺伝子多型から追うアナナスショウジョウバエ亜群の種分化 (生物進化研究のモデル生物群としてのショウジョウバエ)

• 松田 宗男
• 低温科学 69, 29-32, 2011
• … Polytene chromosome data were consistent with molecular data within the bipectinata complex. …
• NAID 40018938265

• Presence of polytene nuclei with chromocenters unassociated with chromatin bundles in Vigna unguiculata

• ,
• Chromosome
• … There are pronounced polytene nuclei with chromocenters unassociated with chromatin bundles. …
• NAID 130000654626

Related Links

• Polytene Chromosomes - eLS: Citable Reviews in the Life ...

Polytene chromosomes are specific interphase chromosomes consisting of thousands of deoxyribonucleic acid (DNA) strands ... Figure 2. Drawing of a polytene chromosome set of Drosophila melanogaster. The chromosomes have ...

• Polytene Chromosomes

Drosophila polytene chromosomes viewed on our microscope. the DNA is stained with DAPI (in blue) and a site on the left arm of chromosome 2 is labeled ... Drosophila polytene chromosomes stained with Orescein and viewed ...

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