The Cell Cycle and Mitosis

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The Cell Cycle and Mitosis

• Biology Chapter 10

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Cell Growth and Reproduction

• What is the NUCLEUS??? Organelle that directs
  the activities of the cell.
• CHROMOSOMES Threadlike material made of DNA
  that determine an organisms characteristics.
  Characteristics are things like
• Eye color, hair color, skin tone, etc.
• A human has 46 chromosomes
• A horse has 60 chromosomes
• A mouse has 40 chromosomes
• Corn has 20 chromosomes

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The Cell Cycle

• The Cell cycle is divided into several stages.
• G1, S, G2 are all called Interphase this is
  about 90 of the cell cycle time.
• G1 Cell Growth
• S (Synthesis phase) DNA Replication.
• G2 Preparation for Mitosis
• M Mitosis Phase

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What is Mitosis

• Approximately 10 trillion cells in the human body
  all arose from a single cell by mitosis. Ex
  red blood cells are made at the rate of one
  million per second!
• Mitosis is the process by which a cell replicates.

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Mitosis

• Mitosis has two basic functions
• Duplicate the cell
• Ensure that each daughter cell has a complete
  copy of the DNA.
• Mitosis makes up about 10 of the cell cycle time.

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Why is Mitosis Important?

• Mitosis is important because it allows organisms
  to grow, and replace worn out or damaged cells.

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Mitosis

• Before cells prepare for Mitosis, its DNA
  molecules are stretched out like threads.
• Each DNA molecule with its protein is a
  chromosome.
• That one protein contributes to a trait (gene)
  that is inherited.
• Each person has 46 chromosomes 23 from Mom and
  23 from Dad.

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Mitosis Steps

• Each time new cells are produced , there is a
  cycle it must go through. Cell division occurs
  in a series of stages, or phases.
• Interphase (Before Mitosis)
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis
• INTELLIGENT People Meet At Three OClock

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Mitosis Steps

• PROPHASE Mitosis begins (cells begin to divide)
• The chromosomes shorten and thicken.
• Centrioles (or poles) appear and begin to move to
  opposite ends of the cell.

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Mitosis Steps

• METAPHASE Chromatids (or pairs of chromosomes)
  attach to spindle fibers and line up along the
  middle of the cell.

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Mitosis Steps

• ANAPHASE Chromatids separate and begin to move
  to opposite ends of the cell.

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Mitosis Steps

• TELOPHASE
• Two new nuclei form.
• Chromosomes appear as chromatin (threads rather
  than rods).
• Mitosis ends
• Spindle fibers dissolve.

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Mitosis Steps

• CYTOKINESIS Cell membrane moves inward to
  create two daughter cells each with its own
  nucleus and identical chromosomes cytoplasm
  pinches into creating TWO IDENTICAL DAUGHTER
  CELLS!!!!

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Regulating the Cell Cycle

• Cyclins
• Proteins that cause spindle fibers to form
• Regulate the timing of the cell cycle in
  eukaryotic cells.
• Two types
• Internal respond to events inside the cell
• Ex. They make sure the cell does not enter
  mitosis until all its chromosomes have been
  replicated.
• External respond to events outside the cell
• Ex. Prevent excessive cell growth and they keep
  the tissues of the body from disrupting each
  other.

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Uncontrolled Cell Growth

• Cancer a disorder in which some of the bodys
  own cells lose the ability to control growth.
• Cancer cells do not respond to the signals that
  regulate the growth of most cells.
• Tumors masses of cells that grow uncontrollably
• Damage surrounding tissues.
• Some causes
• Smoking tobacco
• Exposure to radiation
• Viral infections
• many other causes of cancer.

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Uncontrolled Cell Growth