Structure, function and growth of prokaryote and eukaryote cells

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• Structure, function and growth of prokaryote and
  eukaryote cells
• (ii) Cell growth and Cell cycle
• Interphase
• Mitosis
• Mitotic index
• Control of the cell cycle
• Abnormal Cell division cancer cells

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Cell Control

• There are three checkpoints in the cell cycle.
• Where do you think these are and why?

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Control of Cell Cycle

• G1 Checkpoint
• End of the G1 phase
• Cell size is assessed
• If large enough the cell enters S-phase
• The cell is usually pushed past this point by
  signals (growth factors) from outside the cell

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Control of Cell Cycle G1 cont

• If conditions are met
• DNA replication enzymes called polymerases are
  transcribed to allow S-phase to begin
• If conditions are not met
• Cells dont divide and remain in G0 (roughly
  equivalent to G1)
• Many mature cells e.g. nerve cells, skeletal
  muscle cells, RBCs dont divide

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Control of Cell Cycle

• G2 Checkpoint
• DNA replication success is monitored
• If replication is successful
• DNA polymerase enzymes are deactivated
• Metaphase enzymes are activated (see MPF)
• If replication is unsuccessful
• Any cell with unreplicated or damaged DNA that
  cant be repaired is destroyed (apoptosis cell
  suicide)

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Control of Cell Cycle - MPF

• Mitosis (maturation) Promoting Factor (MPF)
• Promotes transition of G2 to M phase
• Acts as a catalyst for the conversion of
  metaphase enzymes from an inactive to an active
  state (by phosphorylation)

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Control of the Cell Cycle

• M Checkpoint
• Occurs during metaphase
• Checks the spindle has assembled properly
• All chromosomes are attached properly (by the
  kinetochores)
• If conditions are met
• Metaphase enzymes are deactivated
• Anaphase enzymes are activated

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Abnormal Cell Division Cancer

• What do you already know about cancer and its
  causes?

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Abnormal Cell Division Cancer

• Introduction
• Cancer cells by-pass normal cell control
  mechanisms. As a result they divide
  uncontrollably to form lumps of tissue (tumours)
  that no longer carry out their function.

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Mutation to Proliferation Genes

• Normal proliferation genes are called
  Proto-oncogenes
• During normal cell division proto-oncogenes code
  for proteins (e.g. growth factors) that promote
  cell division

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Mutation to Proliferation Genes

• Mutated Proliferation genes are called oncogenes
• Oncogenes act to produce cells that are not
  required.
• E.g.
• Produce a protein which triggers a response in
  the cell as if growth factors are present
• Over production of growth factors

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Mutation to Proliferation Genes

• Oncogenes are dominant
• Only 1 gene in the pair of alleles needs to
  mutate for it to have an effect.
• Mutations in several different genes are usually
  required for cancer to develop.

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Mutation to Anti-proliferation genes

• (AKA Tumour Suppressor Genes)
• Normal Anti-proliferation Genes
• Switch off cell division when something goes
  wrong
• If the cell is damaged beyond repair apoptosis
  occurs

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Mutation to Anti-proliferation Genes..

• Mutations to Anti-proliferation Genes
• Cause the cell to continue dividing when faulty
• E.g. p53 is a protein produced by a
  anti-proliferation gene. It binds to damaged DNA
  stopping cell division until it is repaired. A
  mutation to this gene results in a faulty protein
  and cell division with faulty DNA

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Mutation to Anti-proliferation Genes..

• Mutations to anti-proliferation genes are
  recessive
• Both alleles of the gene are required to be
  mutated for mutation to take affect
• Mutations in several different genes are usually
  required for cancer to develop

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Learning Activities

• Write a brochure or a story to explain what
  cancer is to a young child (assume they know
  about cells).
• Genetic Origins of Cancer worksheet
• Advanced Higher Questions
• Read Dart pg 14-17
• Scholar