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the first stage of meiosis
the first stage of mitosis

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/03/04 05:36:32」(JST)

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Fluorescence microscope image of two mouse cell nuclei in prophase (scale bar is 5 µm).^[1]

Prophase (from the Greek πρό, "before" and φάσις, "stage"), is a stage of mitosis in which the chromatin condenses into double rod-shaped structures called chromosomes in which the chromatin becomes visible. This process, called chromatin condensation, is involved with the condensin complex. Since the genetic material has been replicated in the prior interphase of the cell cycle, there are two identical copies of each chromosome in the cell. Those copies are called sister chromatids and they are attached to each other at a DNA element present on every chromosome called the centromere. Also during prophase, giemsa staining can be applied to elicit G-banding in chromosomes.

An important organelle in mitosis is the centrosome, the microtubule organizing center in metazoans. During prophase, the two centrosomes, which replicate independently of mitosis, have their microtubule-activity increased due to the recruitment of γ-tubulin. The centrosomes will be pushed apart to opposite ends of the cell nucleus by the action of molecular motors acting on the microtubules.

At the end of prophase, the tiny nucleolus within the nucleus dissolves. The nucleolus starts moving towards the nuclear membrane at the beginning of prophase, and its disintegration occurs near the nuclear envelope. Its contents are dispersed in masses.^[2]

Basically, the chromatin in the nucleus coils into chromosomes. The centrosomes move to opposite poles of the cell, forming a bridge of spindle fibers. At the end of prophase, the nucleolus disperses.

In prometaphase, the next step of mitosis, the nuclear membrane breaks apart and the chromosomes are captured by the microtubules which are attached to centromeres.^[3]

References

^ Schermelleh, L.; Carlton, P. M.; Haase, S.; Shao, L.; Winoto, L.; Kner, P.; Burke, B.; Cardoso, M. C.; et al. (2008). "Subdiffraction Multicolor Imaging of the Nuclear Periphery with 3D Structured Illumination Microscopy". Science 320 (5881): 1332–6. Bibcode:2008Sci...320.1332S. doi:10.1126/science.1156947. PMC 2916659. PMID 18535242.
^ Zeng, X.; Jiao, M.; Wang, X.; Song, Z.; Hao, S. (2001). "Electron microscopic studies on the Silver-stained Nucleolar Cycle of Physarum Polycephalum" (PDF). Acta Botanica Cinica 43 (7): 680–5. Retrieved 24 February 2015.
^ Raven, Peter H; Evert, Ray Franklin; Eichhorn, Susan E (2012). "Section 1. The Biology of the Plant Cell – 3. The Plant Cell and the Cell Cycle". Biology of plants. pp. 58–67. ISBN 978-0-7167-1007-3. LCCN 2004053303. OCLC 56051064.

External links

Media related to Prophase at Wikimedia Commons

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English Journal

SIRT1 signalling protects mouse oocytes against oxidative stress and is deregulated during aging.

Di Emidio G1, Falone S1, Vitti M1, D'Alessandro AM1, Vento M2, Di Pietro C3, Amicarelli F1, Tatone C4.
Human reproduction (Oxford, England).Hum Reprod.2014 Sep;29(9):2006-17. doi: 10.1093/humrep/deu160. Epub 2014 Jun 24.
STUDY QUESTION: Is SIRT1 involved in the oxidative stress (OS) response in mouse oocytes SUMMARY ANSWER: SIRT1 plays a pivotal role in the adaptive response of mouse germinal vesicle (GV) oocytes to OS and promotes a signalling cascade leading to up-regulation of the MnSod gene.WHAT IS KNOWN ALREADY
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Contrasting behavior of heterochromatic and euchromatic chromosome portions and pericentric genome separation in pre-bouquetspermatocytes of hybrid mice.

Scherthan H1, Schöfisch K, Dell T, Illner D.
Chromosoma.Chromosoma.2014 Aug 15. [Epub ahead of print]
The spatial distribution of parental genomes has attracted much interest because intranuclear chromosome distribution can modulate the transcriptome of cells and influence the efficacy of meiotic homologue pairing. Pairing of parental chromosomes is imperative to sexual reproduction as it translates
PMID 25119530

Procentriole assembly without centriole disengagement - a paradox of male gametogenesis.

Gottardo M1, Callaini G2, Riparbelli MG1.
Journal of cell science.J Cell Sci.2014 Aug 15;127(Pt 16):3434-9. doi: 10.1242/jcs.152843. Epub 2014 Jun 17.
Disengagement of parent centrioles represents the licensing process to restrict centriole duplication exactly once during the cell cycle. However, we provide compelling evidence that this general rule is overridden in insect gametogenesis, when distinct procentrioles are generated during prophase of
PMID 24938597

Japanese Journal

The promoter of the oocyte-specific gene, oog1, functions in both male and female meiotic germ cells in transgenic mice.

Ishida Miya,Okazaki Eriko,Tsukamoto Satoshi,Kimura Koji,Aizawa Akira,Kito Seiji,Imai Hiroshi,Minami Naojiro
PloS one 8(7), 2013-07-22
… Oog1 is an oocyte-specific gene whose expression is turned on in mouse oocytes at embryonic day (E) 15.5, concomitant with the time when most of the female germ cells stop proliferating and enter meiotic prophase. …
NAID 120005312068

H3S10 Phosphorylation Marks Constitutive Heterochromatin During Interphase in Early Mouse Embryos Until the 4-Cell Stage

RIBEIRO-MASON Karlla,BOULESTEIX Claire,FLEUROT Renaud [他],AGUIRRE-LAVIN Tiphaine,ADENOT Pierre,GALL Laurence,DEBEY Pascale,BEAUJEAN Nathalie
The Journal of reproduction and development 58(4), 467-475, 2012-08-01
… Remarkably, in mammalian somatic cells, H3S10P initiates in the pericentromeric heterochromatin during the late G2 phase, and phosphorylation spreads throughout the chromosomes arms in prophase, being maintained until the onset of anaphase when it gets dephosphorylated. …
NAID 10031067132

Immunolocalization and Expression Pattern of Gpr3 in the Ovary and Its Effect on Proliferation of Ovarian Granulosa Cells in Pigs

ZHANG Baole,WEI Quanwei,SHI Shuai [他],DONG Fulu,SHI Fangxiong,XU Yinxue
The Journal of reproduction and development 58(4), 410-419, 2012-08-01
… Gpr3, a member of the G protein-coupled receptor superfamily, was known as a critical factor for the maintenance of meiotic prophase arrest in oocytes via a Gs protein-mediated pathway. …
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