Cell Division - Mitosis

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Introduction

cartoon of mitosis and meiosis
Mitosis and meiosis

Normal cell division in all cells, except germ cells, occurs by 2 mechanical processes that initially divide the nucleus then the cell cytoplasm. This process produces two (daughter) cells that should be genetically identical to the parent cell.


Germ cells, oocyte and spermatozoa, undergo meiotic cell division.


  • Mitosis segregation of chromosomes and formation of 2 nuclei
  • Cytokinesis splitting of the cell as a whole into 2 daughter cells
  • Recent Nobel Prizes- 2001 Cell Cycle, 2002 Cell Death


Mitosis of the single zygote produces how many cells in the adult?  
Mark Hill.jpg
Not a straightforward calculation! Cells through development and in the adult divide and die influenced by cell type, genetics and environment. In the adult, most tissues though would have a relatively contestant balance between loss and gain in cell numbers. A recent paper has attempted to estimate the number for humans[1] "In particular, the reported total cell number of a human being ranges between 1012 and 1016 and it is widely mentioned without a proper reference. ...A current estimation of human total cell number calculated for a variety of organs and cell types is presented. These partial data correspond to a total number of 3.72 × 1013."


Cell Division Links: Meiosis | Mitosis | Lecture - Cell Division and Fertilization | Spermatozoa Development | Oocyte Development | Fertilization | Zygote | Genetics

Some Recent Findings

  • Review - Mosaicism in Preimplantation Human Embryos: When Chromosomal Abnormalities Are the Norm[2] "Along with errors in meiosis, mitotic errors during post-zygotic cell division contribute to pervasive aneuploidy in human embryos. Relatively little is known, however, about the genesis of these errors or their fitness consequences. Rapid technological advances are helping to close this gap, revealing diverse molecular mechanisms contributing to mitotic error. These include altered cell cycle checkpoints, aberrations of the centrosome, and failed chromatid cohesion, mirroring findings from cancer biology. Recent studies are challenging the idea that mitotic error is abnormal, emphasizing that the fitness impacts of mosaicism depend on its scope and severity. In light of these findings, technical and philosophical limitations of various screening approaches are discussed, along with avenues for future research."
  • Golgi apparatus self-organizes into the characteristic shape via postmitotic reassembly dynamics[3]

"The Golgi apparatus is a membrane-bounded organelle with the characteristic shape of a series of stacked flat cisternae. During mitosis in mammalian cells, the Golgi apparatus is once fragmented into small vesicles and then reassembled to form the characteristic shape again in each daughter cell. The mechanism and details of the reassembly process remain elusive. ...We show that the characteristic Golgi shape is spontaneously organized from the assembly of vesicles by proper tuning of the two additional mechanisms, i.e., the Golgi reassembly process is modeled as self-organization. We also demonstrate that the fine Golgi shape forms via a balance of three reaction speeds: vesicle aggregation, membrane fusion, and shape relaxation. Moreover, the membrane fusion activity decreases thickness and the number of stacked cisternae of the emerging shapes."

  • The nucleoporin ELYS/Mel28 regulates nuclear envelope subdomain formation in HeLa cells[4] "In open mitosis, the nuclear envelope (NE) reassembles at the end of each mitosis. This process involves the reformation of the nuclear pore complex (NPC), the inner and outer nuclear membranes, and the nuclear lamina. In human cells, cell cycle-dependent NE subdomains exist, characterized as A-type lamin-rich/NPC-free or B-type lamin-rich/NPC-rich, which are initially formed as core or noncore regions on mitotic chromosomes, respectively. Although postmitotic NE formation has been extensively studied, little is known about the coordination of NPC and NE assembly. ...Our data show, that ELYS/Mel28 plays a role in NE subdomain formation in late mitosis."
More recent papers  
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This table shows an automated computer PubMed search using the listed sub-heading term.

  • Therefore the list of references do not reflect any editorial selection of material based on content or relevance.
  • References appear in this list based upon the date of the actual page viewing.

References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability.

Links: References | Discussion Page | Pubmed Most Recent | Journal Searches


Search term: Mitosis

Majd Haj, Andrea Wijeweera, Sergei Rudnizky, Jack Taunton, Lilach Pnueli, Philippa Melamed Mitogen and stress-activated protein kinase 1 is required for gonadotropin-releasing hormone-mediated activation of gonadotropin α subunit expression. J. Biol. Chem.: 2017; PubMed 29054929

Zhaojun Qiu, Nancy L Oleinick, Junran Zhang ATR/CHK1 inhibitors and cancer therapy. Radiother Oncol: 2017; PubMed 29054375

Tony Ly, Arlene Whigham, Rosemary Clarke, Alejandro J Brenes-Murillo, Brett Estes, Diana Madhessian, Emma Lundberg, Patricia Wadsworth, Angus I Lamond Proteomic analysis of cell cycle progression in asynchronous cultures, including mitotic subphases, using PRIMMUS. Elife: 2017, 6; PubMed 29052541

Ronghua Wang, Fangming Liu, Yongxu Zhao, Dan Wu, Lihan Chen, Edward T H Yeh, Chao Huang Reversible regulation of ORC2 SUMOylation by PIAS4 and SENP2. Oncotarget: 2017, 8(41);70142-70155 PubMed 29050267

Eun Hee Han, Jin-Young Min, Shin-Ae Yoo, Sung-Joon Park, Yun-Jeong Choe, Hee Sub Yun, Zee-Won Lee, Sun Woo Jin, Hyung Gyun Kim, Hye Gwang Jeong, Hyun Kyoung Kim, Nam Doo Kim, Young-Ho Chung A small-molecule inhibitor targeting the AURKC-IκBα interaction decreases transformed growth of MDA-MB-231 breast cancer cells. Oncotarget: 2017, 8(41);69691-69708 PubMed 29050234

Movies

Mitosis

This movie shows a cell dividing by mitosis with a fluorescently labelled protein that is located at the kinetochores and along the axes of the chromosome arms. This allows you to see the chromosomes and the linking region (kinetochore) between chromosome pairs and the mitotic spindle microtubules.[5]

Mitosis 01 icon.jpg
 ‎‎Mitosis
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Mitosis Links: MP4 movie | Cell Division - Mitosis | Week 1 | Lecture - Cell Division and Fertilization | Movies
Mitosis 01 icon.jpg
 ‎‎Mitosis
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Mouse zygote division icon.jpg
 ‎‎Zygote Mitosis
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Mouse zygote division 02 icon.jpg
 ‎‎Early Division
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Parental genome mix 01 icon.jpg
 ‎‎Parental Genomes
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Human cytokinesis movie 01 icon.jpg
 ‎‎Cytokinesis Mito
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Links: MCB Movie - The stages of mitosis and cytokinesis in an animal cell

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

Mitosis fl.jpg

Prophase

Mammalian cell - prophase
Mammalian cell - prophase[6]
  • 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.
  1. astral microtubules - anchor the pole end in position
  2. kinetochore microtubules - connected to chromosomes
  3. 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.
    • Astrin is a spindle-associated protein required for chromosome alignment at the metaphase plate.[7]

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.
  • Katanin is a microtubule-severing complex involved with this stage of microtubule dynamics.[8]

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

Cleavage of Zygote

Mouse zygote mitosis[9]

Mouse zygote mitosis metaphase.jpg Mouse zygote mitosis anaphase.jpg
First metaphase First anaphase

Cleavage of the zygote forms 2 blastomeres and is cleavage with no cytoplasm synthesis.

  • special "embryonic" cell cycle S phases and M phases alternate without any intervening G1 or G2 phases (MSMSMSMS, adult MG1SG2) therefore individual cell volume decreases

Cell division within these cells is initially synchronous (at the same time), then becomes asynchronously (at different times).

  • slow- centre cells, larger fast- peripheral cells


Links: Zygote | Cell Division - Mitosis | Movie - Early Cell Division | Movie - Week 1 Cell Cleavage | Carnegie stage 1

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

Mitotic Spindle

Spindle assembly motors 01.jpg

Spindle assembly motors[10]

Microtubule (MT)-bound motors promote bipolar spindle formation, whereas chromosome-associated motors drive proper kinetochore orientation and chromosome movement to the equator.

Box 1 Box 2 Box 3 Box 4 Box 5
Motor-dependent mechanisms establish bipolarity as Eg5 (kinesin-5) motors slide antiparallel microtubules apart with their minus ends leading and their plus ends directed toward the spindle equator. Minus end–directed motors such as dynein move microtubules poleward with their minus ends leading, thereby incorporating K-fibers into the spindle and focusing spindle poles. Kinetochore-associated dynein transports chromosomes along astral microtubules toward the spindle poles from the periphery. Plus end–directed chromokinesins (kinesin-4 and -10) eject chromosome arms outward. CENP-E (kinesin-7) transports unattached kinetochores toward the equator along spindle microtubules. MTOC, microtubule organizing centre.

Cell Organelles

Mitochondria

  • Divide independently of cell mitosis
  • distributed into daughter cells

Peroxisomes

  • localise at spindle poles

Mitosis peroxisomes 01.jpg

Peroxisome (red) location at Interphase (a) and during Mitosis (b and c)[11]

Endoplasmic Reticulum

  • Associated with nuclear membrane.

Golgi

  • 2 processes - disassembly and reassembly[12]
  • 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

References

  1. Eva Bianconi, Allison Piovesan, Federica Facchin, Alina Beraudi, Raffaella Casadei, Flavia Frabetti, Lorenza Vitale, Maria Chiara Pelleri, Simone Tassani, Francesco Piva, Soledad Perez-Amodio, Pierluigi Strippoli, Silvia Canaider An estimation of the number of cells in the human body. Ann. Hum. Biol.: 2013, 40(6);463-71 PubMed 23829164
  2. Rajiv C McCoy Mosaicism in Preimplantation Human Embryos: When Chromosomal Abnormalities Are the Norm. Trends Genet.: 2017; PubMed 28457629
  3. Masashi Tachikawa, Atsushi Mochizuki Golgi apparatus self-organizes into the characteristic shape via postmitotic reassembly dynamics. Proc. Natl. Acad. Sci. U.S.A.: 2017; PubMed 28461510
  4. Michaela Clever, Tomoko Funakoshi, Yasuhiro Mimura, Masatoshi Takagi, Naoko Imamoto The nucleoporin ELYS/Mel28 regulates nuclear envelope subdomain formation in HeLa cells. Nucleus: 2012, 3(2);187-99 PubMed 22555603
  5. Penny A Tavormina, Marie-George Côme, Joanna R Hudson, Yin-Yuan Mo, William T Beck, Gary J Gorbsky Rapid exchange of mammalian topoisomerase II alpha at kinetochores and chromosome arms in mitosis. J. Cell Biol.: 2002, 158(1);23-9 PubMed 12105179
  6. Russan NM. Let's Build a Spindle. ASCB Image & Video Library. 2008;CYT-190. Available at: http://cellimages.ascb.org/u?/p4041coll12,521
  7. Anja K Dunsch, Emily Linnane, Francis A Barr, Ulrike Gruneberg The astrin-kinastrin/SKAP complex localizes to microtubule plus ends and facilitates chromosome alignment. J. Cell Biol.: 2011, 192(6);959-68 PubMed 21402792
  8. Dong Zhang, Gregory C Rogers, Daniel W Buster, David J Sharp Three microtubule severing enzymes contribute to the "Pacman-flux" machinery that moves chromosomes. J. Cell Biol.: 2007, 177(2);231-42 PubMed 17452528
  9. Khursheed Iqbal, Seung-Gi Jin, Gerd P Pfeifer, Piroska E Szabó Reprogramming of the paternal genome upon fertilization involves genome-wide oxidation of 5-methylcytosine. Proc. Natl. Acad. Sci. U.S.A.: 2011, 108(9);3642-7 PubMed 21321204 | PMC2132672 | PNAS
  10. Rebecca Heald, Alexey Khodjakov Thirty years of search and capture: The complex simplicity of mitotic spindle assembly. J. Cell Biol.: 2015, 211(6);1103-11 PubMed 26668328
  11. Simone Kredel, Franz Oswald, Karin Nienhaus, Karen Deuschle, Carlheinz Röcker, Michael Wolff, Ralf Heilker, G Ulrich Nienhaus, Jörg Wiedenmann mRuby, a bright monomeric red fluorescent protein for labeling of subcellular structures. PLoS ONE: 2009, 4(2);e4391 PubMed 19194514 | PMC2633614 | PLoS One.
  12. Danming Tang, Kari Mar, Graham Warren, Yanzhuang Wang Molecular mechanism of mitotic Golgi disassembly and reassembly revealed by a defined reconstitution assay. J. Biol. Chem.: 2008, 283(10);6085-94 PubMed 18156178

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Terms

Cell Division Terms  
Meiosis | Mitosis
  • anaphase - (Greek, ana = up, again) Mitosis term referring to the fourth stage, where the paired chromatids now separate and migrate to spindle poles. This is followed by telophase.
  • anaphase A - Mitosis term referring to the part of anaphase during which the chromosomes move.
  • anaphase B - Mitosis term referring to the part of anaphase during which the poles of the mitotic spindle move apart.
  • aster - (Latin, aster = star) star-like object visible in most dividing eukaryotic cells contains the microtubule organizing center.
  • astral microtubule - spindle apparatus microtubule (MT) originating from the centrosome which does not connect to a kinetochore. These microtubules only exist during mitosis, the other spindle types are polar and kinetochore microtubules.
  • bouquet stage - meiosis term for when in prophase transition to the zygotene stage, the chromosome telomeres attachment to the inner nuclear envelope and form a cluster. This occurs before the onset of homologous pairing and synapsis. The name comes from the chromosomes resembling a "bouquet of flowers".
  • diploid - (Greek, di = double + ploion = vessel) having two sets of chromosomes, the normal state for all cells other than the animal gametes that are haploid (a single set of chromosomes).
  • diplotene stage- (diplotene phase, diplonema; Greek, diplonema = "two threads") meiotic stage seen during prophase I, the chromosomes separate from one another a small amount giving this appearance. In the developing human ovary, oocytes remain at the diplotene stage from fetal life through postnatal childhood, until puberty when the lutenizing hormone (LH) surges stimulate the resumption of meiosis. Prophase I, is divided into 5 stages (leptotene, zygotene, pachytene, diplotene, diakinesis) based upon changes associated with the synaptonemal complex structure that forms between two pairs of homologous chromosomes.
  • FUCCI - Acronym for Fluorescence Ubiquitination Cell Cycle Indicator a molecular tool for identifying the stage in the cell cycle. In G0/G1 cells express a red fluorescent protein and S/G2/M cells express a green fluorescent protein. (More? Tooth Development Movie)
  • haploid - (Greek, haploos = single) Having a single set of chromosomes as in mature germ/sex cells (oocyte, spermatozoa) following reductive cell division by meiosis. Normally cells are diploid, containing 2 sets of chromosomes. Ploidy refers to the number of sets of chromosomes in the nucleus of a cell.
  • homologous chromosomes - meiosis term for the two matching (maternal and one paternal) chromosomes that align during meiosis I.
  • kinetochore - the protein structure formed on chromatids where the spindle kinetochore microtubules attach during cell division.
  • kinetochore microtubule - spindle apparatus microtubule (MT) that attaches to the chromosome kinetochore by its plus end, the other spindle types are astral and polar microtubules.
  • kinesin - a microtubule (MT) motor protein that exists in many isoforms and most move towards the MT positive end. Different isoforms have different functions within the spindle apparatus. PMID 20109570
  • meiosis - reductive cell division required to produce germ cells (oocyte, spermatozoa) and for sexual reproduction. Note that only spermatozoa complete meiosis before fertilisation. Chromosome number is reduced from diploid to haploid, during this process maternal and paternal genetic material are exchanged. All other non-germ cells in the body divide by mitosis. (More? Meiosis | Spermatozoa Development | Oocyte Development | Week 1)
  • meiosis I - (MI) the first part of meiosis resulting in separation of homologous chromosomes, in humans producing two haploid cells (N chromosomes, 23), a reductional division.
  • meiosis II - (MII) the second part of meiosis. In male human spermatogenesis, producing of four haploid cells (23 chromosomes, 1N) from the two haploid cells (23 chromosomes, 1N), each of the chromosomes consisting of two sister chromatids produced in meiosis I. In female human oogenesis, only a single haploid cell (23 chromosomes, 1N) is produced. Meiosis II: Prophase II - Metaphase II - Anaphase II - Telophase II.
  • meiotic silencing of unsynapsed chromatin - (MSUC) an aneuploidy protective mechanism for subsequent generations, during meiosis where chromosomes are silenced that fail to pair with their homologous partners.
  • merotelic kinetochore - cell division abnormality in chromosomal attachment that occurs when a single kinetochore is attached to microtubules arising from both spindle poles. Normal chromosomal attachment in early mitosis, is by only one of the two sister kinetochores attached to spindle microtubules (monotelic attachment) later sister kinetochores attach to microtubules arising from opposite spindle poles (amphitelic attachment).
  • metaphase - mitosis term referring to the third stage where mitotic spindle kinetochore microtubules align chromosomes in one midpoint plane. Metaphase ends when sister kinetochores separate. Originally based on light microscopy of living cells and electron microscopy of fixed and stained cells. A light microscope analysis called a "metaphase spread" was originally used to detect chromosomal abnormalities in cells. Mitosis Phases: prophase - prometaphase - metaphase - anaphase - telophase
  • metaphase spread - In mitosis using light microscope analysis originally used to detect chromosomal abnormalities in cells, as chromosomes are only visible during cell division.
  • microfilament - (MF) cytoskeleton filament normally required for cytoplasmic intracellular transport, motility and cell shape. Named by the actin monomers assembling into the smallest in cross-section of the three filament systems (microtubules and intermediate filaments). This system is disassembled and reassembled as the contractile ring for cytokinesis (cytoplasm division) following cell division mitosis and meiosis.
  • microtubule - (MT) cytoskeleton filament normally required for cytoplasmic intracellular transport and motility. Named by the tubulin monomers assembling into "tubes", and are the largest in cross-section of the three filament systems (microfilaments and intermediate filaments). This system is disassembled and reassembled as the spindle apparatus during cell division.
  • mitosis - (M phase) The normal division of all cells, except germ cells, where chromosome number is maintained (diploid). In germ cell division (oocyte, spermatozoa) meiosis is a modified form of this division resulting in reduction in genetic content (haploid). Mitosis, division of the nucleus, is followed by cytokinesis the division of the cell cytoplasm and the cytoplasmic contents. cytokinesis overlaps with telophase.
  • p - chromosome short arm (possibly French, petit) and used along with chromosome and band number to indicate genes located on this arm of the chromosome. The chromosome long arm is identified as q (possibly French, tall) chosen as next letter in alphabet after p. These chromosomal arms are only seen when the chromosome is folded for cell division.
  • polar microtubule - spindle apparatus microtubule (MT) that can arise from either pole and overlap at the spindle midzone. This interdigitating structure consisting of antiparallel microtubules is responsible for pushing the poles of the spindle apart. The other spindle types are astral and kinetochore microtubules.
  • prometaphase - (Greek, pro = before) mitosis term referring to the second stage, when the nuclear envelope breaks down into vesicles. Microtubules then extend from the centrosomes at the spindle poles (ends) and reach the chromosomes. This is followed by metaphase.
  • pronuclear fusion - (Greek, pro = before) the process of the fusion of the two haploid nuclear structures (pronuclei) contributed from the spermatazoa and oocyte to form the first diploid nucleus cell. Can also be called "fusion of pronuclei".
  • pronucleus - (Greek, pro = before; plural, pronuclei) the two haploid nuclei or nuclear structures containing the genetic material from the spermatozoa and the oocyte. These two haploid nuclei will fuse together to form the first diploid nucleus cell, the zygote. Therefore the nuclear structures that exist "before the nucleus", the plural term is pronuclei.
  • prophase - (Greek, pro = before) - mitosis term referring to the first stage, when the diffusely stained chromatin resolves into discrete chromosomes, each consisting of two chromatids joined together at the centromere.
  • prophase I - meiosis term refers to the first phase of meiosis I, which together with meiosis II results in the reductive cell division only occurring gametes. Prophase can be further divided into a number of stages: leptotene zygotene, pachytene, diplotene, diakinesis.
  • q - chromosome long arm (possibly French, tall), the next letter in alphabet after p, and used along with chromosome and band number to indicate genes located on this arm of the chromosome. The chromosome short arm is identified as p (possibly French, petit). These chromosomal arms are only seen when the chromosome is folded for cell division.
  • S phase - during interphase of cell cycle where DNA is duplicated prior to second growth period (G2 phase) that is followed by mitosis (M phase).
  • synapsis - (syndesis) meiosis term for the pairing of two homologous chromosomes that occurs during prophase I.
  • synaptonemal complex - meiosis term for a protein structure essential for synapsis of homologous chromosomes. (proteins SCP3 and SCP1).
  • telomere - region found at each end of the chromosome and involved in cellular ageing and the capacity for division. The regions consist of repeated sequences protecting the ends of chromosomes and harbour DNA repair proteins. In the absence of the enzyme telomerase, these regions shorten during each cell division and becoming critically short, cell senescence occurs.
  • telophase - mitosis term referring to the fifth stage, where the vesicles of the nuclear envelope reform around the daughter cells, the nucleoli reappear and the chromosomes unfold to allow gene expression to begin. This phase overlaps with cytokinesis, the division of the cell cytoplasm.
  • telomerase - the enzyme that maintains the chromosome end length, the telomeres, involved in cellular ageing and the capacity for division. Absence of telomerase activity leads to the chromosome ends shorten during each cell division, becoming critically short and cell senescence then occurs.
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Cite this page: Hill, M.A. 2017 Embryology Cell Division - Mitosis. Retrieved October 24, 2017, from https://embryology.med.unsw.edu.au/embryology/index.php/Cell_Division_-_Mitosis

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