Results for prophase
On this page:
 
Dictionary:

prophase

  (prō'fāz') pronunciation
n.
  1. The first stage of mitosis, during which the chromosomes condense and become visible, the nuclear membrane breaks down, and the spindle apparatus forms at opposite poles of the cell.
  2. The first stage of meiosis, constituted by a series of events that include the thickening and coiling of the chromosomes, synapsis of homologous chromosomes, tetrad formation, and crossing over.
prophasic pro·pha'sic (-fā'zĭk) adj.
 
 

The first stage of cell replication in either meiosis or mitosis.

 
Wikipedia: prophase
Newt lung cell in Prophase, with the mitotic spindles stained green and the cell nucleus and chromatin stained blue.
Enlarge
Newt lung cell in Prophase, with the mitotic spindles stained green and the cell nucleus and chromatin stained blue.
An illustration of prophase in Gray's Anatomy. The chromatin has condensed.
Enlarge
An illustration of prophase in Gray's Anatomy. The chromatin has condensed.


Prophase is a stage of mitosis in which chromatin condenses into a highly ordered structure called a chromosome (it is at this stage giemsa staining can be applied to elicit G-banding in chromosomes). This process, called chromatin condensation, is mediated by the condensin complex. Since the genetic material has been duplicated, there are two identical copies of each chromosome in the cell. Identical chromosomes, called sister chromatids, are attached to each other at a DNA element present on every chromosome called the centromere.

When chromosomes are paired up and attached, each individual chromosome in the pair is called a chromatid, while the whole unit is called a chromosome. When the chromatids separate, they are no longer called chromatids, but are called chromosomes again. The task of mitosis is to assure that one copy of each sister chromatid - and only one copy - goes to each daughter cell after cell division.

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-nucleating activity increased due to the recruitement 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. The nuclear envelope breaks down to allow the microtubules to reach the kinetochores on the chromosomes. The nuclear envelope break down marks the end of prophase. Prometaphase, the next step of mitosis will see the chromosome being captured by the microtubules.

Prophase in plant cells

The cells of lower plants (such as the flowering plants) undergo a series of events preparing them for mitosis before the onset of prophase. In highly vacuolated plant cells, the nucleus has to migrate into the center of the cell before mitosis can begin. This is achieved during the G2 phase of the cell cycle through the formation of a phragmosome, a transverse sheet of cytoplasm that bisects the cell along the future plane of cell division.

Prophase in plant cells is preceded by a preprophase stage only found in plants. Preprophase is characterized by the formation of a ring of microtubules and actin filaments (called preprophase band) underneath the plasmamembrane around the equatorial plane of the future mitotic spindle and predicting the position of cell plate fusion during telophase. The preprophase band disappears during nuclear envelope disassembly and spindle formation in prometaphase.

The cells of higher plants lack centrioles. Instead, the nuclear envelope serves as a microtubule organizing center. Spindle microtubules aggregate on the surface of the nuclear envelope during preprophase and prophase, forming the prophase spindle.[1]



 
Translations: Translations for: Prophase

Dansk (Danish)
n. - profase

Nederlands (Dutch)
eerste fase in de celdeling

Français (French)
n. - prophase

Deutsch (German)
n. - Prophase (Stadium in der Zellteilung)

Ελληνική (Greek)
n. - πρόφαση (πρώτη φάση της πυρηνικής διαίρεσης)

Italiano (Italian)
profase

Português (Portuguese)
n. - prófase (f) (Biol.)

Русский (Russian)
профаза

Español (Spanish)
n. - profase

Svenska (Swedish)
n. - förstadium, profas (biol.)

中文(简体) (Chinese (Simplified))
前期

中文(繁體) (Chinese (Traditional))
n. - 前期

한국어 (Korean)
n. - (유사분열의) 전기

日本語 (Japanese)
n. - 前期

العربيه (Arabic)
‏(الاسم) الطور الأول في انقسام الخليه‏

עברית (Hebrew)
n. - ‮השלב הראשון בחלוקת תאי הצמח או החי - התכווצות כרומוזומים‬


 
 

Join the WikiAnswers Q&A community. Post a question or answer questions about "prophase" at WikiAnswers.

 

Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Prophase" Read more
Translations. Copyright © 2007, WizCom Technologies Ltd. All rights reserved.  Read more

Search for answers directly from your browser with the FREE Answers.com Toolbar!  
Click here to download now. 

Get Answers your way! Check out all our free tools and products.

On this page:   E-mail   print Print  Link  

 

Keep Reading

Mentioned In: