Cell Division - Mitosis: Difference between revisions

Revision as of 17:06, 14 July 2010

Introduction

Features 2 mechanical processes

Mitosis segregation of chromosomes and formation of 2 nuclei
Cytokinesis splitting of the cell as a whole into 2 daughter cells

Cell Division Milestones
Recent Nobel Prizes- 2001 Cell Cycle, 2002 Cell Death

Cell Changes

Nucleus
- Chromosome condensation
- Nuclear envelope breakdown

Cytoplasm
- Cytoskeleton reorganization
- Spindle formation (MT) Contractile ring (MF)
- Organelle redistribution

Mitosis Energy
- Cell division uses up a lot of energy, so cells ensure they have enough resources to complete the job before committing to it.

Mitosis Phases

Based on light microscopy of living cells light and electron microscopy of fixed and stained cells
5 Phases - prophase, prometaphase, metaphase, anaphase, and telophase
- Cytokinesis 6th stage overlaps the end of mitosis

MBC The stages of mitosis and cytokinesis in an animal cell

Interphase

not a mitotic phase (discussed in cell cycle)
Chromosomes dispersed in nucleus
Gene expression
Cytoskeleton and cell organelles - Distributed and functioning
Mitochondria undergo independent proliferation/division

Chromosome Changes

Prophase

Mammalian cell - prophase^[1]

Chromosome DNA has been earlier duplicated (S Phase)
Chromosomes begin condensing
Chromosome pairs (chromatids) held together at centromere

Microtubules disassemble
Mitotic spindle begins to form

Spindle Apparatus

3 sets of microtubules - (+) ends point away from centrosome at each pole.

astral microtubules - anchor the pole end in position
kinetochore microtubules - connected to chromosomes
polar microtubules - form the structure of the spindle apparatus

Spindle Apparatus EM | Spindle Apparatus | MBC Movie- Microtubule dynamics during mitosis

At end of prophase nuclear envelope breaks down

Prometaphase

Microtubules now enter nuclear region
Nuclear envelope forms vesicles around mitotic spindle
Kinetochores form on centromere attach to some MTs of spindle

Dynamic instability and the capture of chromosomes

Centromeric attachment of microtubules

At end of prometaphase chromosomes move to metaphase plate

Metaphase

Mitosis - Metaphase

Kinetochore MTs align chromosomes in one midpoint plane

Proposed alternative mechanisms for chromosome congression

Metaphase ends when sister kinetochores separate

Anaphase

Chromosome motility anaphase

Separation of sister Kinetochores
shortening of Kinetochore microtubules pulls chromosome to spindle pole

Experiment - during anaphase A chromosomes move poleward along stationary kinetochore microtubules, which coordinately disassemble from their kinetochore ends

Anaphase ends as nuclear envelope (membrane) begins to reform

Telophase

Mitosis - Telophase

Chromosomes arrive at spindle poles
Kinetochore MTs lost
Condensed chromosomes begin expanding
- Continues through cytokinesis

Links: Figure 19-41 Microtubule dynamics during mitosis | Figure 19-34. The stages of mitosis and cytokinesis in an animal cell | Cytokinetic abscission: cellular dynamics at the midbody

Cytokinesis

Division of cytoplasmic contents
Contractile ring forms at midpoint under membrane
Microfilament ring - contracts forming cleavage furrow
- myosin II is the motor
Eventually fully divides cytoplasm

Links: Cytokinesis | Cytokinesis in Plants

Cell Organelles

Mitochondria

Divide independently of cell mitosis
distributed into daughter cells

Peroxisomes

localise at spindle poles

Endoplasmic Reticulum

Golgi

File:Post-mitotic Golgi stack formation.png

Post-mitotic Golgi stack formation

2 processes - disassembly and reassembly
Golgi stack undergoes a continuous fragmentation process
fragments are distributed into daughter cells
are reassembled into new Golgi stacks

Disassembly

Unstacking - mediated by two mitotic kinases (cdc2 and plk)
Vesiculation - mediated by COPI budding machinery ARF1 and the coatomer complex

Reassembly

Fusion - formation of single cisternae by membrane fusion
Restacking - requires dephosphorylation of Golgi stacking proteins by protein phosphatase PP2A

Links: Tang D, Mar K, Warren G, Wang Y. Molecular mechanism of mitotic Golgi disassembly and reassembly revealed by a defined reconstitution assay. J Biol Chem. 2008 Mar 7;283(10):6085-94. Epub 2007 Dec 21. PMID: 18156178

Some Recent Findings

References

↑ Russan NM. Let's Build a Spindle. ASCB Image & Video Library. 2008;CYT-190. Available at: http://cellimages.ascb.org/u?/p4041coll12,521

Reviews

Articles

Search Pubmed

Search Pubmed: mitosis

Additional Images

Cite this page: Hill, M.A. (2024, June 26) Embryology Cell Division - Mitosis. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Cell_Division_-_Mitosis

What Links Here?

[1] Russan NM. Let's Build a Spindle. ASCB Image & Video Library. 2008;CYT-190. Available at: http://cellimages.ascb.org/u?/p4041coll12,521

[1]

@@ Line 1: / Line 1: @@
 == Introduction ==
+Features 2 mechanical processes
+* Mitosis segregation of chromosomes and formation of 2 nuclei
+* Cytokinesis splitting of the cell as a whole into 2 daughter cells
+* [http://www.nature.com/celldivision/milestones/index.html Cell Division Milestones]
+* Recent Nobel Prizes-  2001 Cell Cycle, 2002 Cell Death
+==Cell Changes==
+* Nucleus
+** Chromosome condensation
+** Nuclear envelope breakdown
+* Cytoplasm
+** Cytoskeleton reorganization
+** Spindle formation (MT) Contractile ring (MF)
+** Organelle redistribution
+* Mitosis Energy
+** Cell division uses up a lot of energy, so cells ensure they have enough resources to complete the job before committing to it.
+==Mitosis Phases==
+* Based on light microscopy of living cells light and electron microscopy of fixed and stained cells
+* 5 Phases - prophase, prometaphase, metaphase, anaphase, and telophase
+** Cytokinesis 6th stage overlaps the end of mitosis
+[http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mcb&part=A5499&rendertype=figure&id=A5500 MBC The stages of mitosis and cytokinesis in an animal cell]
+Interphase
+* not a mitotic phase (discussed in cell cycle)
+* Chromosomes dispersed in nucleus
+* Gene expression
+* Cytoskeleton and cell organelles - Distributed and functioning
+* Mitochondria undergo independent proliferation/division
+==Chromosome Changes==
+[[Image:Mitosis fl.jpg]]
+===Prophase ===
+[[File:Mammalian cell - prophase.jpg|thumb|Mammalian cell - prophase<ref>Russan NM. Let's Build a Spindle. ASCB Image & Video Library. 2008;CYT-190. Available at: http://cellimages.ascb.org/u?/p4041coll12,521</ref>]]
+* Chromosome DNA has been earlier duplicated (S Phase)
+* Chromosomes begin condensing
+* Chromosome pairs (chromatids) held together at centromere
+* Microtubules disassemble
+* Mitotic spindle begins to form
+====Spindle Apparatus====
+* 3 sets of microtubules -  (+) ends point away from centrosome at each pole.
+# astral microtubules - anchor the pole end in position
+# kinetochore microtubules - connected to chromosomes
+# polar microtubules - form the structure of the spindle apparatus
+[http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mboc4&part=A3349&rendertype=figure&id=A3350 Spindle Apparatus EM] | [http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mcb&part=A5499&rendertype=figure&id=A5505 Spindle Apparatus] | [http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mcb&part=A5499&rendertype=figure&id=A5514 MBC Movie- Microtubule dynamics during mitosis]
+At end of prophase nuclear envelope breaks down
+===Prometaphase===
+* Microtubules now enter nuclear region
+* Nuclear envelope forms vesicles around mitotic spindle
+* Kinetochores form on centromere attach to some MTs of spindle
+[http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mcb&part=A5499&rendertype=figure&id=A5520 Dynamic instability and the capture of chromosomes]
+[http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mcb&part=A5499&rendertype=figure&id=A5509 Centromeric attachment of microtubules]
+At end of prometaphase chromosomes move to metaphase plate
+===Metaphase===
+[[File:Mitosis_-_Metaphase.jpg|thumb|Mitosis - Metaphase]]
+* Kinetochore MTs align chromosomes in one midpoint plane
+[http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mcb&part=A5499&rendertype=figure&id=A5522 Proposed alternative mechanisms for chromosome congression]
+Metaphase ends when sister kinetochores separate
+===Anaphase===
+[[Image:Chromosome_motility_anaphase.jpg|thumb|Chromosome motility anaphase]]
+* Separation of sister Kinetochores
+* shortening of Kinetochore microtubules pulls chromosome to spindle pole
+[http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mcb&part=A5499&rendertype=figure&id=A5526 Experiment - during anaphase A chromosomes move poleward along stationary kinetochore microtubules, which coordinately disassemble from their kinetochore ends]
+Anaphase ends as nuclear envelope (membrane) begins to reform
+===Telophase===
+[[File:Mitosis - Telophase.jpg|thumb|Mitosis - Telophase]]
+* Chromosomes arrive at spindle poles
+* Kinetochore MTs lost
+* Condensed chromosomes begin expanding
+** Continues through cytokinesis
+'''Links:''' [http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mcb&part=A5499&rendertype=figure&id=A5514 Figure 19-41 Microtubule dynamics during mitosis] | [http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mcb&part=A5499&rendertype=figure&id=A5500 Figure 19-34. The stages of mitosis and cytokinesis in an animal cell] | [http://www.cell.com/trends/cell-biology/fulltext/S0962-8924(09)00158-5 Cytokinetic abscission: cellular dynamics at the midbody]
+==Cytokinesis==
+* Division of cytoplasmic contents
+* Contractile ring forms at midpoint under membrane
+* Microfilament ring - contracts forming cleavage furrow
+** myosin II is the motor
+* Eventually fully divides cytoplasm
+'''Links:''' [http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=cooper&part=A1790&rendertype=figure&id=A1802 Cytokinesis] | [http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mboc4&part=A3381&rendertype=figure&id=A3396 Cytokinesis in Plants]
+== Cell Organelles ==
+===Mitochondria===
+* Divide independently of cell mitosis
+* distributed into daughter cells
+===Peroxisomes===
+* localise at spindle poles
+===Endoplasmic Reticulum===
+===Golgi===
+[[Image:Post-mitotic Golgi stack formation.png|thumb|Post-mitotic Golgi stack formation]]
+* 2 processes - disassembly and reassembly
+* Golgi stack undergoes a continuous fragmentation process
+* fragments are distributed into daughter cells
+* are reassembled into new Golgi stacks
+'''Disassembly'''
+* Unstacking - mediated by two mitotic kinases (cdc2 and plk)
+* Vesiculation - mediated by COPI budding machinery ARF1 and the coatomer complex
+'''Reassembly'''
+* Fusion - formation of single cisternae by membrane fusion
+* Restacking - requires dephosphorylation of Golgi stacking proteins by protein phosphatase PP2A
+Links: Tang D, Mar K, Warren G, Wang Y. Molecular mechanism of mitotic Golgi disassembly and reassembly revealed by a defined reconstitution assay. J Biol Chem. 2008 Mar 7;283(10):6085-94. Epub 2007 Dec 21. PMID: 18156178
 ==Some Recent Findings==