Cell Cycle

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Cell Cycle
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How do cells make more cells?

• They grow and divide!
• The process of cells growing and dividing is
  known as the cell cycle.
• Why do cells need to do this? Hmmm
• Cell cycle cells growing and dividing

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Stages of Cell Cycle

• There are 3 stages
• Interphase
• Mitosis
• Cytokinesis
• All of the cell cycle occurs in the nucleus!

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Parts to know

• We need to understand some parts of the cell
  before we begin looking at each step.
• Centrioles
• Chromatin
• DNA
• Chromosomes

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Centrioles

• Come in pairs
• Look like a macaroni noodle or barreled shape
• Found in the cytoplasm
• Like to hang out at the north pole of the cell
• They are orange here

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Centrioles
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Chromatin

• Definition Mass of genetic material composed of
  DNA and proteins.
• Chromatin is located in the nucleus of a cell.
• During mitosis (2nd stage), chromatin condenses
  to form chromosomes.

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DNA in Chromatin

• I mentioned that chromatin
• is made of DNA.
• What is DNA?
• DNA, or deoxyribonucleic acid, is the hereditary
  material in humans and almost all other
  organisms.
• Most DNA is located in the cell nucleus.
• So, chromatin is composed of DNA and chromatin
  condenses to form chromosomes.

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Chromosomes

• Once again chromatin is composed of DNA and
  chromatin condenses to form chromosomes.
• What are chromosomes?
• It is a single piece of coiled DNA

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Chromosomes
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Structure of Chromosome
The centromere acts like a button. It keeps the
2 chromatids together making the double rod X
structure.
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Stage 1- Interphase

• Interphase Growth Phase
• This is the period where the cell grows and
  prepares for division.  It is divided into three
  parts
• G1 The cell grows
• S The cell replicates its chromosomes (DNA).
• G2 The cell replicates its organelles and
  prepares for division.

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Stage 1- Interphase

• During interphase, the chromosomes are not
  visible.  They are uncoiled.  When the DNA is in
  this uncoiled form its called chromatin. 
• The reason its uncoiled is this allows it to be
  copied more easily.

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Stage 1- Interphase

• The cell spends most of its life in the
  interphase stage.

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Visit Stage 1- Interphase

• http//www.phschool.com/atschool/phsciexp/active_a
  rt/cell_cycle/index.html
• Now the cell is ready to divide. Next stage

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Stage 2 - Mitosis

• Mitosis Division of the Nucleus
• This is divided into four steps
• Prophase
• Metaphase
• Anaphase
• Telophase

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Stage 2 MitosisStep 1 Prophase

• Chromatin condenses to form chromosomes
• Centrioles move to opposite ends of cell
• Nuclear envelope starts to break down.

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Visit Mitosis Step 1 Prophase

• http//www.phschool.com/atschool/phsciexp/active_a
  rt/cell_cycle/index.html
• Time to move to the next step of mitosis

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Stage 2 MitosisStep 2 Metaphase

• The chromosomes line up in the MIDDLE of the
  cell.
• The centrioles are at north south poles.
• MMMMetaphase..MMMMiddle

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Visit Mitosis Step 2 Metaphase

• http//www.phschool.com/atschool/phsciexp/active_a
  rt/cell_cycle/index.html
• Time to move to the next step of mitosis

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Stage 2 MitosisStep 3 Anaphase

• Remember the centromeres
• that act like a button and hold
• the chromosomes together?
• Well, not anymore. The centromeres break.
• Thus, the chromosome is seperated and becomes two
  chromatids again.
• Each chromataid moves
• to opposite ends of cell.
• AAAnaphaseAAAway

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Visit Mitosis Step 3 Anaphase

• http//www.phschool.com/atschool/phsciexp/active_a
  rt/cell_cycle/index.html
• Time to move to the last step of mitosis

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Stage 2 MitosisStep 4 Telophase

• A new nuclear envelope has formed around each
  region of chromosomes
• TTTwo Nucleus(Nuclei)TTTelophase

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Stage 2 Mitosis.Step 4 Telophase

• http//www.phschool.com/atschool/phsciexp/active_a
  rt/cell_cycle/index.html
• The last step of mitosis.

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Stage 3 - Cytokinesis

• cyto- (cell) and kinesis (motion, movement)
• Cytokinesis is the process in which the cytoplasm
  of a single eukaryotic cell is divided to form
  two daughter cells.

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Stage 3 - Cytokinesis

• http//www.phschool.com/atschool/phsciexp/active_a
  rt/cell_cycle/index.html
• A look at the last stage of the cell cycle.