Mitosis Overview

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Mitosis Overview
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Objectives

• Name and describe the two types of reproduction.
• Explain what happens during the cell cycle.
• Explain what happens in the stages of mitosis.
• Discuss how mitotic cell division in unicellular
  and multicellular organisms are controlled.

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Terms to know

• -mitosis -cytokinesis
• -interphase -prophase
• -metaphase -anaphase
• -telophase -cell cycle
• -asexual reproduction -chromosomes
• -sexual reproduction -binary fission
• -budding -spores
• -gametes -chromatin

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Why must cells divide

• Cells must divide in order for an organism to be
  able to
• Grow
• Maintain and repair body tissues
• Reproduce

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Function of mitotic cell division

• Mitosis is important for the growth, maintenance,
  repair, reproduction of eukaryotic body cells.
• Kidney, liver, skin, heart, pancreas cells etc.
  all reproduce by mitotic cell divisions.
• Mitosis results in 2 daughter cells that have the
  exact same DNA as the mother cells.

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Two major types of reproduction

1. Asexual reproduction Only 1 parent organism
   reproduces by itself, no sex cells are involved.
   Offspring are genetically identical to parent.
2. Sexual reproduction Two parent organisms
   reproduce to form a new organism. Gametes or sex
   cells (sperm and egg) are involved. Offspring are
   contains genes from both parents.

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Two types of reproduction

• Asexual reproduction occurs in single celled
  organisms, some plants, and some animals.
• Sexual reproduction occurs in most animals and
  plants.

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Cell Division

• Before it becomes too large, a growing cell must
  divide forming two daughter cells.
• The process by which a cell divides into two new
  daughter cells is called cell division.

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Cell Division

• Before cell division occurs, the cell replicates,
  or copies, all of its DNA.
• This replication of DNA solves the problem of
  information storage because each new daughter
  cell gets one complete set of genetic
  information.
• Thus, each daughter cell now contains its own
  genetic library.

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The cell cycle and mitosis

• During the cell cycle, a cell grows, prepares for
  division, and divides to form two daughter cells
  each of which then begins the cycle again.
• Mitosis A process of the cell cycle that occurs
  when a cell with a distinct nucleus divides to
  form two daughter cells.

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5 Phases of the cell cycle

1. The cell grows and develops (G1)
2. The genetic material is replicated inside the
   parent cell (S)
3. The cell continues to grow and develop (G2)
4. The nucleus divides in two separating the genetic
   material into two equal parts (mitosis)
5. The cytoplasm divides forming two new daughter
   cells (cytokinesis)

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Cell cycle and mitosis
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Questions

• What does the nucleus contain and why must it
  divide?
• What kinds of cells can undergo mitosis?
• (eukaryotic or prokaryotic)

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Mitosis and changes in the nucleus

• DNA is the genetic information needed to make
  important cell structures. It also determines how
  the organism will look, behave, and function.
• Before a cell divides, the DNA must be replicated
  so that each new daughter cell has a copy of the
  information.

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Mitosis and changes in the nucleus

• Before the cell divides, the DNA in the nucleus
  appears as loose fibers called chromatin.
• Before mitosis begins, the DNA must be
  replicated.
• As the cell enters mitosis, the chromatin coils
  up into structure called chromosomes.

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Mitosis and changes in the nucleus

• Imagine Each strand of DNA within each of your
  cells is about 6 feet long. The DNA becomes so
  tightly coiled into the chromosomes that it can
  actually fit into a microscopic cell!!
• Humans have 46 chromosomes in each of our body
  cells.

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What exactly is a chromosome?

• Chromosomes are composed of tightly coiled DNA
  and proteins called histones, which allow the DNA
  to coil into these compact structures.
• Chromosomes contain genes which code for various
  traits.

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Chromatid
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Mitosis and changes in the nucleus

• During cell division, before mitosis, it is the
  chromosomes that duplicate.
• Why must the chromosomes duplicate before mitosis?

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Interphase and Mitosis

• When a cell is not dividing, it is in interphase.
• During interphase the cell
• Grows in size
• Replicates its chromosomes (they double in
  number)
• Metabolic activity is at its highest

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Mitosis Division of the nucleus

• Mitosis involve 4 phases.
• Prophase
• Metaphase
• Anaphase
• Telophase
• Plainedge Made A Touchdown

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Prophase

• The chromatin thickens and coils into chromosomes
• The nuclear membrane disappears
• Mitotic spindle fibers form from centrioles

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Metaphase

• Spindle fibers align the chromosomes along the
  middle of the cell nucleus. This line is called
  the metaphase plate.
• This organization helps to ensure that in the
  next phase, when the chromosomes are separated,
  each new nucleus will receive one copy of each
  chromosome.

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Anaphase

• The paired chromosomes separate at the
  kinetochores and move to opposite sides of the
  cell.
• Kinetochore part of chromosomes where spindle
  fiber attaches
• Motion results from a combination of kinetochore
  movement along the spindle microtubules

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Kinetochore and Spindle Microtubules
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Telophase

• Chromatids arrive at opposite poles of cell, and
  new membranes form around the daughter nuclei.
• The chromosomes disperse and are no longer
  visible under the light microscope.
• The spindle fibers disperse, and cytokinesis or
  the partitioning of the cell may also begin
  during this stage.

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Cytokinesis

• In animal cells, cytokinesis results when a fiber
  ring composed of a protein called actin around
  the center of the cell contracts pinching the
  cell into two daughter cells, each with one
  nucleus.
• In plant cells, the rigid wall requires that a
  cell plate be synthesized between the two
  daughter cells.

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Whitefish Mitosis
prophase
interphase
metaphase
anaphase
telophase
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What Phase is this?

• Prophase
• Nuclear membrane is gone.
• DNA condensed into chromosomes

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How about this?

• Anaphase
• Chromosomes are being pulled apart to opposite
  ends of the cell.

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What Phase is this?

• Telophase
• Nuclear membrane has reappeared
• DNA is now in chromatin form.
• Cell membrane pinches cell into 2 new daughter
  cells.

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What Phase is this?

• Metaphase
• Chromosomes are lined up in the center of the
  cell.
• Spindle fiber network is visible

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What Phase is this?

• Interphase
• Nuclear membrane is visible
• DNA in form of chromatin.

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Related Websites

• http//www.cellsalive.com/mitosis.htm
• http//www.biology.arizona.edu/cell_bio/tutorials/
  cell_cycle/cells3.html
• http//www.sci.sdsu.edu/multimedia/mitosis/
• http//biologyinmotion.com/cell_division/
• http//www.life.umd.edu/CBMG/faculty/wolniak/wolni
  akmitosis.html
• http//www.bio.unc.edu/faculty/salmon/lab/mitosis/
  mitosis.html