Prometaphase: Difference between revisions
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{{short description|Stage of cell division}} |
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<!-- Deleted image removed: [[Image:Prometaphase-flourescent.jpg|thumb|left|In early prometaphase, the nuclear membrane has just degraded, allowing the [[microtubule]]s to quickly interact with the kinetochores on the chromosomes, which have just condensed.]] --> |
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[[File:Prometaphase.svg|thumb|300px]] |
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[[File:PLoSBiol3.5.Fig1bNucleus46Chromosomes.jpg|thumb|200px|The 23 human chromosome territories during prometaphase in [[fibroblast]] cells.]] |
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<!-- Deleted image removed: [[Image:Prometaphase-flourescent2.jpg|thumb|160px|In late prometaphase, most of the chromosomes have begun the events of [[metaphase]] while the rest should have at least have one kinetochore connected.]] --> |
<!-- Deleted image removed: [[Image:Prometaphase-flourescent2.jpg|thumb|160px|In late prometaphase, most of the chromosomes have begun the events of [[metaphase]] while the rest should have at least have one kinetochore connected.]] --> |
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| ⚫ | [[File:Prometaphase.svg|thumb]]'''Prometaphase''' is the phase of [[mitosis]] following [[prophase]] and preceding [[metaphase]] in [[eukaryote|eukaryotic]] [[Somatic (biology)|somatic]] [[Cell (biology)|cell]]s. In prometaphase, the [[nuclear membrane]] breaks apart into numerous "membrane vesicles," and the chromosomes inside form protein structures called [[kinetochores]].<ref name="Nature Education">{{cite web|title=prometaphase|url=http://www.nature.com/scitable/definition/prometaphase-281|publisher=Nature Education|access-date=9 December 2012}}</ref> Kinetochore microtubules emerging from the centrosomes at the poles (ends) of the spindle reach the chromosomes and attach to the kinetochores,<ref name="Nature Education" /> throwing the chromosomes into agitated motion.<ref name="Campbell Biology">{{Cite book|last=Reece| first=Jane B. | title = The Cell Cycle | edition = 9th | year = 2011 | publisher = Pearson Education, Inc. | location = San Francisco | chapter = 12 }}</ref> Other spindle microtubules make contact with microtubules coming from the opposite pole. Forces exerted by protein "motors" associated with spindle microtubules move the chromosomes toward the centre of the cell.[[File:Stages of early mitosis in a vertebrate cell with micrographs of chromatids.svg|thumb|right|Stages of early mitosis in a vertebrate cell with micrographs of chromatids]] |
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'''Prometaphase''' is the phase of [[mitosis]] following [[prophase]] and preceding [[metaphase]], in [[eukaryote|eukaryotic]] [[Somatic (biology)|somatic]] [[Cell (biology)|cell]]s. Prometaphase is sometimes simply included as part of the end of prophase and early metaphase. |
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Prometaphase is not always presented as a distinct part of mitosis. In sources that do not use the term, the events described here are instead assigned to late prophase and early metaphase. |
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| ⚫ | In prometaphase, the [[nuclear membrane]] breaks apart into numerous "membrane vesicles |
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==Types of microtubules== |
==Types of microtubules== |
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==Transition from prometaphase to metaphase== |
==Transition from prometaphase to metaphase== |
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The role of prometaphase is completed when all of the kinetochore microtubules have attached to their kinetochores, upon which [[metaphase]] begins. An unattached kinetochore, and thus a non-aligned chromosome, even when most of the other chromosomes have lined up, will trigger the [[spindle checkpoint]] signal. This prevents premature progression into [[anaphase]] by inhibiting the [[anaphase-promoting complex]] until all kinetochores are attached and all the chromosomes aligned.<ref name="Journal of Cell Science">{{cite journal|last=May|first=Karen M|author2=Kevin G. Hardwick |title=The spindle checkpoint|journal=Journal of Cell Science|url=http://jcs.biologists.org/content/119/20/4139.full| |
The role of prometaphase is completed when all of the kinetochore microtubules have attached to their kinetochores, upon which [[metaphase]] begins. An unattached kinetochore, and thus a non-aligned chromosome, even when most of the other chromosomes have lined up, will trigger the [[spindle checkpoint]] signal. This prevents premature progression into [[anaphase]] by inhibiting the [[anaphase-promoting complex]] until all kinetochores are attached and all the chromosomes aligned.<ref name="Journal of Cell Science">{{cite journal|last=May|first=Karen M|author2=Kevin G. Hardwick |title=The spindle checkpoint|journal=Journal of Cell Science|url=http://jcs.biologists.org/content/119/20/4139.full|access-date=9 December 2012|pmid=17038540|doi=10.1242/jcs.03165|year=2006|volume=119|issue=Pt 20|pages=4139–42|doi-access=}}</ref> |
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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. |
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. |
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Latest revision as of 15:31, 7 March 2024
Prometaphase is the phase of mitosis following prophase and preceding metaphase in eukaryotic somatic cells. In prometaphase, the nuclear membrane breaks apart into numerous "membrane vesicles," and the chromosomes inside form protein structures called kinetochores.[1] Kinetochore microtubules emerging from the centrosomes at the poles (ends) of the spindle reach the chromosomes and attach to the kinetochores,[1] throwing the chromosomes into agitated motion.[2] Other spindle microtubules make contact with microtubules coming from the opposite pole. Forces exerted by protein "motors" associated with spindle microtubules move the chromosomes toward the centre of the cell.
Prometaphase is not always presented as a distinct part of mitosis. In sources that do not use the term, the events described here are instead assigned to late prophase and early metaphase.
Types of microtubules
[edit]The microtubules are composed of two types, kinetochore microtubules and non-kinetochore microtubules.
- Kinetochore microtubules begin searching for kinetochores to attach to.
- A number of non-kinetochore microtubules or polar microtubules find and interact with corresponding nonkinetochore microtubules from the opposite centrosome to form the mitotic spindle.
Transition from prometaphase to metaphase
[edit]The role of prometaphase is completed when all of the kinetochore microtubules have attached to their kinetochores, upon which metaphase begins. An unattached kinetochore, and thus a non-aligned chromosome, even when most of the other chromosomes have lined up, will trigger the spindle checkpoint signal. This prevents premature progression into anaphase by inhibiting the anaphase-promoting complex until all kinetochores are attached and all the chromosomes aligned.[3]
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.
References
[edit]- ^ a b "prometaphase". Nature Education. Retrieved 9 December 2012.
- ^ Reece, Jane B. (2011). "12". The Cell Cycle (9th ed.). San Francisco: Pearson Education, Inc.
- ^ May, Karen M; Kevin G. Hardwick (2006). "The spindle checkpoint". Journal of Cell Science. 119 (Pt 20): 4139–42. doi:10.1242/jcs.03165. PMID 17038540. Retrieved 9 December 2012.
External links
[edit]
Media related to Prometaphase at Wikimedia Commons
