Metaphase


Metaphase
In metaphase, the chromosomes align in the middle of the cell.
Immunofluorescent image of a cell in metaphase showing microtubules in green, chromosomes (DNA) in blue, and kinetochores in pink

Metaphase, from the ancient Greek μετά (between) and φάσις (stage), is a stage of mitosis in the eukaryotic cell cycle in which condensed & highly coiled chromosomes, carrying genetic information, align in the middle of the cell before being separated into each of the two daughter cells. Metaphase accounts for approximately 4% of the cell cycle's duration. Preceded by events in prometaphase and followed by anaphase, microtubules formed in prophase have already found and attached themselves to kinetochores in metaphase. The centromeres of the chromosomes convene themselves on the metaphase plate (or equatorial plate), an imaginary line that is equidistant from the two centrosome poles. This even alignment is due to the counterbalance of the pulling powers generated by the opposing kinetochores, analogous to a tug of war between equally strong people. In certain types of cells, chromosomes do not line up at the metaphase plate and instead move back and forth between the poles randomly, only roughly lining up along the middleline. Early events of metaphase can coincide with the later events of prometaphase, as chromosomes with connected kinetochores will start the events of metaphase individually before other chromosomes with unconnected kinetochores that are still lingering in the events of prometaphase.

One of the cell cycle checkpoints occurs during prometaphase and metaphase. Only after all chromosomes have become aligned at the metaphase plate, when every kinetochore is properly attached to a bundle of microtubules, does the cell enter anaphase. It is thought that unattached or improperly attached kinetochores generate a signal to prevent premature progression to anaphase, even if most of the kinetochores have been attached and most of the chromosomes have been aligned. Such a signal creates the mitotic spindle checkpoint. This would be accomplished by regulation of the anaphase-promoting complex, securin, and separase.

Metaphase in cytogenetics and cancer studies

Human metaphase chromosomes (normal male karyogram)

The analysis of metaphase chromosomes is one of the main tools of classical cytogenetics and cancer studies. Chromosomes are condensed(Thickened) and highly coiled in metaphase, which makes them most suitable for visual analysis. Metaphase chromosomes make the classical picture of chromosomes (karyotype). For classical cytogenetic analyses, cells are grown in short term culture and arrested in metaphase using mitotic inhibitor. Further they are used for slide preparation and banding (staining) of chromosomes to be visualised under microscope to study structure and number of chromosomes (karyotype). Staining of the slides, often with Giemsa (G banding) or Quinacrine, produces a pattern of in total up to several hundred bands. Normal metaphase spreads are used in methods like FISH and as a hybridization matrix for comparative genomic hybridization (CGH) experiments.

Malignant cells from solid tumors or leukemia samples can also be used for cytogenetic analysis to generate metaphase preparations. Inspection of the stained metaphase chromosomes allows the determination of numerical and structural changes in the tumor cell genome, for example, losses of chromosomal segments or translocations, which may lead to chimeric oncogenes, such as bcr-abl in chronic myelogenous leukemia.

External links


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Metaphase — Métaphase La métaphase est la troisième phase de la mitose (ou deuxième phase de la mitose si on considère la prométaphase et la métaphase comme une seule étape), après la prophase et la prométaphase. C est le rassemblement des chromosomes… …   Wikipédia en Français

  • métaphase — [ metafaz ] n. f. • 1887; de méta et phase ♦ Biol. Deuxième phase de la mitose. ● métaphase nom féminin Deuxième phase de la mitose, caractérisée par la disposition des chromosomes, qui forment la plaque équatoriale. métaphase n. f. BIOL Deuxième …   Encyclopédie Universelle

  • metaphase — metaphase. См. метафаза. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Metaphase — Metaphase, 2. Phase der ⇒ Mitose und der ⇒ Meiose …   Deutsch wörterbuch der biologie

  • metaphase — [met′ə fāz΄] n. [ META + PHASE1] Biol. the stage in mitosis and meiosis, after the prophase and before the anaphase, during which the chromosomes are arranged along the equatorial plane of the spindle …   English World dictionary

  • Metaphase — Schematische Darstellung der Mitose I: Interphase; II: Prophase; III: Prometaphase; IV: Metaphase; V und VI: Anaphase; VII: Telophase; VIII: Zytokinese Als Mitose (zu griechisch μίτος = Faden) (auch Karyokinese) bezeichnet man den Vorgang der Z …   Deutsch Wikipedia

  • Métaphase — La métaphase est la troisième phase de la mitose (ou deuxième phase de la mitose si on considère la prométaphase et la métaphase comme une seule étape), après la prophase et la prométaphase. C est le rassemblement des chromosomes condensés à l… …   Wikipédia en Français

  • metaphase — Classically the second phase of mitosis or one of the divisions of meiosis. In this phase the chromosomes are well condensed and aligned along the metaphase plate, making it an ideal time to examine the chromosomes in a cytological preparation… …   Dictionary of molecular biology

  • metaphase — The stage of mitosis or meiosis in which the chromosomes become aligned on the equatorial plate of the cell separating the centromeres. In mitosis and in the second meiotic division, the centromeres of each chromosome divide and the two daughter… …   Medical dictionary

  • Metaphase — Me|ta|pha|se 〈f. 19; Biol.〉 bestimmtes Stadium der Kernteilung einer Zelle [<grch. meta „mitten, zwischen, nach, hinter“ + Phase] * * * Metaphase,   Phase der Zellteilung. * * * Me|ta|pha|se, die; , n [aus ↑meta , ↑Me …   Universal-Lexikon


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.