The%20Cell%20Cycle

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Chapter 9

• The Cell Cycle

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Cell Division Key Terms

• Genome cells genetic information
• Somatic (body cells) cells
• Gametes (germ cells) sperm and egg cells
• Chromosomes DNA molecules
• Diploid (2n) 2 sets of chromosomes
• Haploid (1n) 1 set of chromosomes

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Cell Division Key Terms

• Chromatin DNA-protein complex
• Chromatids replicated strands of a chromosome
• Centromere narrowing waist of sister
  chromatids
• Mitosis nuclear division
• Cytokinesis cytoplasm division
• Meiosis gamete cell division

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Purpose of cell division

• Multicellular organisms depend on cell division
  for
• Development from a fertilized cell
• Growth
• Repair

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The Cell Cycle

• Interphase (90 of cycle)
• G1 phase growth
• S phase synthesis of DNA
• G2 phase preparation for cell division

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The Cell Cycle

• Mitotic phase
• Mitosis nuclear division
• Cytokinesis cytoplasm division

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Mitosis

• Prophase
• Prometaphase
• Metaphase
• Anaphase
• Telophase

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Mitosis Animation
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Spindle microtubules
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Prophase

• Chromosomes visible
• Nucleoli disappear
• Sister chromatids
• Mitotic spindle forms
• Centrosomes move

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Prometaphase

• Nuclear membrane fragments
• Spindle interaction with chromosomes
• Kinetochore develops

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Metaphase

• Centrosomes at opposite poles
• Centromeres are aligned
• Kinetochores of sister chromatids attached to
  microtubules (spindle)

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Anaphase

• Paired centromeres separate sister chromatids
  liberated
• Chromosomes move to opposite poles
• Each pole now has a complete set of chromosomes

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Telophase

• Daughter nuclei form
• Nuclear envelopes reappear
• Chromatin becomes less coiled
• Two new nuclei complete mitosis

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Cytokinesis

• Cytoplasmic division
• Animals cleavage furrow

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Cytokinesis

• In plant cells, during cytokinesis
• A cell plate forms

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Binary Fission

• Prokaryotes (bacteria)
• Reproduce by a type of cell division called
  binary fission
• The bacterial chromosome replicates
• The two daughter chromosomes actively move apart

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Binary Fission
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The Evolution of Mitosis

• Since prokaryotes preceded eukaryotes by billions
  of years
• It is likely that mitosis evolved from bacterial
  cell division
• Certain protists
• Exhibit types of cell division that seem
  intermediate between binary fission and mitosis
  carried out by most eukaryotic cells

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Cell Cycle Regulation

• Growth factors
• Density-dependent inhibition
• Anchorage dependence

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The Cell Cycle Control System

• The sequential events of the cell cycle

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The clock has specific checkpointsWhere the cell
cycle stops until a go-ahead signal is received
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The Cell Cycle Clock Cyclins and
Cyclin-Dependent Kinases

• Two types of regulatory proteins are involved in
  cell cycle control
• Cyclins and cyclin-dependent kinases (Cdks)

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Loss of Cell Cycle Controls in Cancer Cells

• Cancer cells
• Do not respond normally to the bodys control
  mechanisms
• Form tumors

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Cancer

• Transformation
• Tumor benign or malignant
• Metastasis