MitosisMitosis enables organisms to Mitosis enables organisms to growgrow, , repairrepair

and and replacereplace damaged or lost parts. damaged or lost parts. The process of mitosis produces two new The process of mitosis produces two new

cells from one. cells from one. These new cells have These new cells have identicalidentical chromosome chromosome

sets to the parent cell.sets to the parent cell.Mitosis is a Mitosis is a continuous continuous process once begun, process once begun,

but for reference we divide the process into but for reference we divide the process into several stages.several stages.

Interphase

During interphase the cell is During interphase the cell is functioning functioning normallynormally. . Inside the nucleus the chromosomes Inside the nucleus the chromosomes are present as indistinguishable are present as indistinguishable threads known as threads known as chromatinchromatin..Centrioles are present.Centrioles are present.

Prophase

Chromatin in the nucleus begins to condense and becomes visible Chromatin in the nucleus begins to condense and becomes visible under the light microscope as under the light microscope as chromosomeschromosomes. . The The nuclear membrane nuclear membrane disappears. disappears. CentriolesCentrioles begin moving to begin moving to opposite ends of the cell and fibres extend from the centromeres. opposite ends of the cell and fibres extend from the centromeres. Some fibres start to cross the cell to form the mitotic spindle.Some fibres start to cross the cell to form the mitotic spindle.

Metaphase

Spindle fibres align the chromosomes along the middle of the cell Spindle fibres align the chromosomes along the middle of the cell nucleus, attached to the nucleus, attached to the centromerecentromere. This line is referred to as the . This line is referred to as the metaphase plate or metaphase plate or equatorequator. . This organization helps to ensure that in the next phase, when the This organization helps to ensure that in the next phase, when the chromosomes are separated, each new nucleus will receive one chromosomes are separated, each new nucleus will receive one copy of each chromosome.copy of each chromosome.

Anaphase

The paired chromosomes separate at the The paired chromosomes separate at the centromere and move along the spindle fibre to centromere and move along the spindle fibre to opposite poles of the cell. opposite poles of the cell.

Telophase and Cytokinesis

Chromatids Chromatids arrive at opposite arrive at opposite poles of cell, and new nuclear poles of cell, and new nuclear membranes form around the membranes form around the daughter nuclei. daughter nuclei.

The chromosomes lengthen and The chromosomes lengthen and are no longer visible under the are no longer visible under the light microscope. The spindle fibres disperse, and light microscope. The spindle fibres disperse, and cytokinesiscytokinesis or or the partitioning of the cell may also begin during this stage.the partitioning of the cell may also begin during this stage.

The cell cycle

In animal cells, cytokinesis results when a fibre ring In animal cells, cytokinesis results when a fibre ring composed composed of a protein around the centre of the cell contracts of a protein around the centre of the cell contracts pinching the cell into pinching the cell into two daughter cellstwo daughter cells, each with , each with one nucleus.one nucleus.In plant cells, the rigid wall requires that a In plant cells, the rigid wall requires that a cell plate cell plate be synthesized between the two daughter cells. be synthesized between the two daughter cells. Click on the links below to view animations: http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/MitosisFlash.html http://iknow.net/cell_div_education.html http://iknow.net/cell_div_education.html

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Can you label each of the stage of Mitosis Can you label each of the stage of Mitosis and place them in correct order?and place them in correct order?

References http://www.ias.unt.edu/~tpp001/

Mitosis_Diagram_Page.main.html http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/

cells3.html http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/

MitosisFlash.html http://iknow.net/cell_div_education.html

Collated by Debbie Alam2012