Mitotic cell division

MITOTIC CELL DIVISION

  • Its essential functions, five stages, and relevance to human biology 


Learning outcomes:

  • The Spindle Enables Chromosome Movement During Mitosis

  • Mitotic Cell Division Performs Many Essential Bodily Functions

    • Adult Stem Cells Reproduce (Divide) By Mitotic Cell Division

    • Mitotic Cell Division Ensures That Each Independent “Daughter Cell” Receives A Nucleus With 46 Chromosomes, A Complete Set Of Organelles, Is The Correct Size, And Can Perform Its Bodily Function

  • Mitotic Cell Division Occurs During The Mitotic (M) Phase Of The Cell Cycle 

  • Mitotic Cell Division Consists Of Two Major Events Called Mitosis And Cytokinesis 

    • Mitosis Consists Of Five Stages (PPMAT)

      •  Each Stage Is Defined By Specific Cellular Events And Chromosome Structure

    • After Mitosis Is Complete, The Cell Physically Separates Into Two Identical “Daughter Cells” During Cytokinesis


Stage of the Eukaryotic cell cycle:

  • G1 - S - G2 - parts of interphase 

  • prophase

  • prometaphase

  • metaphase

  • anaphase

  • telophase 


The spindle moves chromosomes during mitosis

  • The spindle is formed from many protein filaments called microtubules

  • Each microtubules is formed form the polymerization of tubulin proteins 


Spindle microtubules attach to a structure on each chromosome called the kinetochore

  • The kinetochore consists of proteins that bind to the centromere nucleotide sequence (think of a handle, that's how it grabs onto the chromosomes)



Mitotic cell division enables cells to reproduce

  • Single-celled eukaryotes use mitotic cell division to reproduce asexually and also to eliminate 

    • Defective organelles and toxins 


Mitotic cell division enables your existence

  • It supplies new cells enabling you to - 

    • Defend yourself (White Blood cells) 

    • Grow including hair 

    • renew/replace/repair

  • Adult stem cells in your bone marrow produce ~100-500 billion new blood cells daily 


Mitotic cell division occurs during mitotic (M) phase (mitosis and cytokinesis) 

  • It forms two, independent, functional, daughter cells with - 

    • 46 DNA molecules in the nucleus 

    • A complete set of organelles and other cellular structures 

    • The exact size required to perform bodily functions 


Mitotic cel division consists mitosis and cytokinesis

  • Mitosis enables the cell to duplicate the nucleus 

    • Mitosis produces two nuclei in the adult stem cell to ensure that each daughter cell inherits a nucleus with 46 DNA molecules (Chromosomes) 


Prophase - the 1st stage of mitosis 

  • Chromatin molecules condense into shorter chromosomes that are easier for the spindle to move

  • The cytokinesis and large organelles(ER, Golgi Apparatus, Nucleus) Disassemble

  • The Spindle becomes functional  


Prometaphase - the 2nd stage of mitosis

  • Kinetochore forms at the centromere of each sister chromatid 

  • Spindle microtubules attach to each kinetochore

  • The spindle moves all 46 pairs of sister chromatids towards the cell center 


Metaphase - 3rd stage of mitosis 

  • The spindle positions all 46 pairs of sister chromatids at the cell center (Equator) to form the metaphase plate 

  • The mitotic phase (Spindle) checkpoint verifies the attachment of spindle microtubules to every kinetochore


Anaphase is the 4th stage of mitosis 

  • The spindle delivers 46 chromosomes to the opposite ends of the cell

    • Each chromatic is attached to a different half of the spindle to ensure that each end of the cell receives 46 chromosomes. 


Telophase is the 5th stage of mitosis 

  • Each chromosome unwinds into its longer chromatin form 

  • Golgi apparatus and ER reform 

  • Nuclear envelope reforms around the 46 chromatin molecules at the opposite ends of the cell to form two nuclei 

  • Spindle disassembles 

    • Released tubulin proteins reform the cytoskeleton in each daughter cell


Cytokinesis begins after mitosis is complete 

  • The cell physically separates to produce two daughter cells

    • Myosin and Microfilament interactions constrict the cell membrane to enable cell separation


M Phase (Spindle) Checkpoint failure 

  • Nondisjunction occurs when the spindle cannot separate one or more pairs of sister chromatids 

    • Nondisjunction causes aneuploidy (Abnormal Chromosome #) 

      • Many Aneuploid cells self-destruct by Apoptosis

      • Aneuploidy increases rate of aging, Risk of cancer risk, and suppresses immunity