ランプブラシ染色体

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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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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/12/23 23:41:38」(JST)

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Lampbrush chromosome from the cell nucleus of an ovarial egg from Triton sp., a salamander.

Lampbrush chromosomes (first seen by Flemming in 1882) are a special form of chromosomes that are found in the growing oocytes (immature eggs) of most animals, except mammals.^[1] Lampbrush chromosomes of tailed and tailless amphibians, birds and insects are described best of all.^[2]^[3]^[4] Chromosomes transform into the lampbrush form during the diplotene stage of meiotic prophase I due to an active transcription of many genes. They are highly extended meiotic half-bivalents, each consisting of 2 sister chromatids. Lampbrush chromosomes are clearly visible even in the light microscope, where they are seen to be organized into a series of chromomeres with large chromatin loops extended laterally. Amphibian and avian lampbrush chromosomes can be microsurgically isolated from oocyte nucleus (germinal vesicle) with either forceps or needles.^[5]^[6]

A given loop always contains the same DNA sequence, and it remains extended in the same manner as the oocytes grows. These chromosomes are producing large amounts of RNA for the oocyte, and most of the genes present in the DNA loops are being actively expressed. Each lateral loop contains one or several transcription units with polarized RNP-matrix coating the DNA axis of the loop.^[7]^[8]^[9] The majority of the DNA, however, is not in loops but remains highly condensed in the chromomeres on the axis, where genes are generally not expressed.

It is thought that the interphase chromosomes of all eukaryotes are similarly arranged in loops. Although these loops are normally too small and fragile to be easily observed in a light microscope, other methods can be used to infer their presence. For example, it has become possible to assess the frequency with which two loci along an interphase chromosome are paired with each other, thus revealing candidates for the sites on chromatin that form the closely apposed bases of loop structures. These experiments and others suggest that the DNA in human chromosomes is organized into loops of different lengths. A typical loop might contain between 50,000 and 200,000 nucleotide pairs of DNA, although loops of a million nucleotide pairs have also been suggested.

Giant chromosomes in the lampbrush form are useful model for studying chromosome organization, genome function and gene expression during meiotic prophase, since they allow the individual transcription units to be visualized.^[10] Moreover lampbrush chromosomes are widely used for high-resolution mapping of DNA sequences and construction of detail cytological maps of individual chromosomes.^[11]

For more information see http://www.projects.ex.ac.uk/lampbrush/

Notes

^ Flemming W (1882) Zellsubstanz, Kern- und Zelltheilung. Vogel, Leipzig.
^ Callan HG (1986) Lampbrush Chromosomes. Springer-Verlag, Berlin, Heidelberg. 252pp.
^ Morgan, G.T. (2002) Lampbrush chromosomes and associated bodies: new insights into principles of nuclear structure and function. Chromosome Research. 10: 177 - 200.
^ Gaginskaya E, Kulikova T, Krasikova A (2009) Avian Lampbrush Chromosomes: a Powerful Tool for Exploration of Genome Expression. Cytogenet Genome Res. V.124. P.251-267.
^ Gall JG (1966) Techniques for the study of lampbrush chromosomes. In: Prescott DM (ed) Methods in cell physiology, vol II. Academic Press, London New York, pp 37-60.
^ Macgregor HC, Varley J (1988) Working with Animal Chromosomes. 2nd edition. John Wiley & Sons.
^ Macgregor HC (1984) Lampbrush chromosomes and gene utilisation in meiotic prophase. In: Controlling Events in Meiosis, W. Evans and H.G.Dickinson (Editors). The Company of Biologists. P 333-348.
^ Morgan, G.T. (2002) Lampbrush chromosomes and associated bodies: new insights into principles of nuclear structure and function. Chromosome Research. 10: 177 - 200.
^ Gaginskaya E, Kulikova T, Krasikova A (2009) Avian Lampbrush Chromosomes: a Powerful Tool for Exploration of Genome Expression. Cytogenet Genome Res. V.124. P.251-267.
^ Morgan, G.T. (2002) Lampbrush chromosomes and associated bodies: new insights into principles of nuclear structure and function. Chromosome Research. 10: 177 - 200.
^ Gaginskaya E, Kulikova T, Krasikova A (2009) Avian Lampbrush Chromosomes: a Powerful Tool for Exploration of Genome Expression. Cytogenet Genome Res. V.124. P.251-267.

References

Flemming W (1882) Zellsubstanz, Kern- und Zelltheilung. Vogel, Leipzig.
Rückert J (1892) Zur Entwicklungsgeschichte des Ovarialeies bei Selachiern. Anat Anz 7: 107-158.
Gall JG (1966) Techniques for the study of lampbrush chromosomes. In: Prescott DM (ed) Methods in cell physiology, vol II. Academic Press, London New York, pp 37–60.
Callan HG (1986) Lampbrush Chromosomes. Springer-Verlag, Berlin, Heidelberg. 252pp.
Macgregor HC (1984) Lampbrush chromosomes and gene utilisation in meiotic prophase. In: Controlling Events in Meiosis, W. Evans and H.G.Dickinson (Editors). The Company of Biologists. P 333-348.
Macgregor HC, Varley J (1988) Working with Animal Chromosomes. 2nd edition. John Wiley & Sons.
Morgan, G.T. (2002) Lampbrush chromosomes and associated bodies: new insights into principles of nuclear structure and function. Chromosome Research. 10: 177 - 200.
Alberts, Johnson, Lewis, Raff, Roberts, Walter (2008), "Molecular biology of the cell" 5th edition. (p234-235).
Gaginskaya E, Kulikova T, Krasikova A (2009) Avian Lampbrush Chromosomes: a Powerful Tool for Exploration of Genome Expression. Cytogenet Genome Res. V.124. P.251-267.

External links

Wikimedia Commons has media related to: Chromosomes

A site introducing a remarkable form of chromosome that exists during the extended diplotene phase of meiosis in the growing ovarian eggs of all animals except mammals. Compiled and edited by Herbert Macgregor, School of Biosciences, University of Exeter.
Methods for making lampbrush chromosome preparations from oocytes of birds

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English Journal

Chromomeres revisited.

Macgregor HC.SourceSchool of Biosciences, University of Exeter, Exeter, EX4 4SB, UK, herbert.macgregor@btinternet.com.
Chromosome research : an international journal on the molecular, supramolecular and evolutionary aspects of chromosome biology.Chromosome Res.2012 Sep 7. [Epub ahead of print]
The history of studies on the chromomeres of lampbrush chromosomes is outlined and evidence for the nature and function of these structures is collected and summarised. Chromomeres and their associated loops on lampbrush chromosomes are not genetic units although in some special cases, they consist
PMID 22956230

Superresolution imaging of transcription units on newt lampbrush chromosomes.

Kaufmann R, Cremer C, Gall JG.SourceKirchhoff Institute for Physics (KIP), University of Heidelberg, Heidelberg, Germany.
Chromosome research : an international journal on the molecular, supramolecular and evolutionary aspects of chromosome biology.Chromosome Res.2012 Aug 15. [Epub ahead of print]
We have examined transcription loops on lampbrush chromosomes of the newt Notophthalmus by superresolution microscopy. Because of the favorable, essentially two-dimensional morphology of these loops, an average optical resolution in the x-y plane of about 50 nm was achieved. We analyzed the distrib
PMID 22892678

Japanese Journal

25. Pairing behavior of sex lampbrush chromosomes in Hynobius leechii(Urodela, Hynobiidae)(Abstracts of the 50th Annual Meeting of the Society of Chromosome Research)

IKEBE Chikako,OHTANI Hiromi,KOHNO Sei-ichi
Chromosome
NAID 110003723692

Polymorphism of Lampbrush Chromosomes in Japanese Populations of Rana nigromaculata

Ohtani Hiromi
Zoological science 11(2), 337-342, 1994-04-15
… The 13 pairs of the lampbrush chromosomes of R. … nigromaculata are characterized by one to five landmarks situated at specific positions on the axis of each chromosome. … nigromaculata collected from 28 sites in Japan, eight chromosome pairs did not show any variations, whereas the remaining five pairs consisted of two forms of chromosome which differed in the number or type of the landmarks. …
NAID 110003323193

Asymmetrical DNA and AT/GC base content of differential sector of Pleurodeles waltl: sexual bivalent: a quantitative fluorescence imaging analysis in lampbrush chromosomes