Cellular Reproduction

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Ch. 9

• Cellular Reproduction

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I. Cellular Growth

• - Cells grow until they reach their size limit,
  then they either stop growing or divide.

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A. Cell Size Limitations

• - Why are cells so small?

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1. Ratio of Surface Area to Volume

• - As a cell grows, its volume increases faster
  than its surface area.

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1. Ratio of Surface Area to Volume

• - As a cell grows, its volume increases faster
  than its surface area.

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1. Ratio of Surface Area to Volume

• - As a cell grows, its volume increases faster
  than its surface area.
• - Large cells dont have enough surface area
  (cell membrane) to support the cell with food and
  oxygen by diffusion.

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2. Transport of Substances

• - Most materials (O2, CO2, water, wastes, etc.)
  enter and exit the cell by diffusion.
• - Diffusion is efficient only over very short
  distances.

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3. Cellular Communications

• - If the cell is too large, it cannot make
  proteins fast enough to support itself.

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B. The Cell Cycle

• - Cell reproduction enables an organism to grow,
  heal injuries, or to reproduce.

Sea Urchin Embryo
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B. The Cell Cycle

• - Cell reproduction enables an organism to grow,
  heal injuries, or to reproduce.

Mitotic cell division Differentiation
Multicell stage (embryo)
Fertilized egg (zygote)
Tissues
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Asexual Reproduction by Mitosis
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Asexual Reproduction by Mitosis
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• - The cell cycle is a continuous process
  consisting of 3 stages Interphase, Mitosis,
  and Cytokinesis.
• - Takes place in 12 24 hours.

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1. Interphase

• - Stage of normal cell activity, growth, and DNA
  replication.
• - Occurs in 3 phases

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• a) G1 cell growth and normal activity
• b) S DNA replication
• - Chromosomes structure in nucleus that
  contain DNA
• - Chromatin active, extended form of
  chromosomes
• c) G2 preparation for mitosis

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Chromosome Structure
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2. Mitosis

• - Division of the nucleus

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3. Cytokinesis

• - Division of the cell into 2 identical
  daughter cells

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4. Prokaryotic Cell Division

• - Binary fission simple cell division

E. coli
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Binary Fission in Bacteria
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Binary Fission in Bacteria
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II. Cell Division

• - Mitosis and Cytokinesis
• A. Mitosis
• - 4 stages (P, M, A, T)

Prophase
Anaphase
Metaphase
Telophase
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1. Prophase

• - first and longest stage
• a. Chromatin condenses to form chromosomes.
• - Each replicated chromosome consists of 2
  identical sister chromatids
• attached at the centromere.

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Human Chromosomes
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• b. Nuclear membrane and nucleoli disappear.
• c. Spindle fibers form
• - microtubule structures that aid in movement
  of chromosomes
• d. Centrioles move to opposite ends of the
  cell (animal cells only).

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2. Metaphase

• - second and shortest stage
• - Chromosomes line up along the middle of the
  cell.

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3. Anaphase

• - Centromeres split and chromosomes move apart to
  opposite sides of the cell.

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4. Telophase

• - last stage
• - "reverse" of prophase
• a. Chromosomes revert to chromatin.
• b. Spindle fibers disappear.
• c. Nuclear membrane and nucleolus reform.

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B. Cytokinesis

• 1. Animal Cells
• - Cell membrane pinches in forming 2 daughter
  cells.

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2. Plant Cells

• - Cell plate forms between 2 daughter cells.

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Which stage of the cell cycle?
Anaphase
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Which stage of the cell cycle?
Interphase
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Which stage of the cell cycle?
Metaphase
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Which stage of the cell cycle?
Prophase
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Which stage of the cell cycle?
Telophase
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Which stages of the cell cycle?
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Which stage of the cell cycle?
Early Anaphase
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Which stage of the cell cycle?
Metaphase
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Which stage of the cell cycle?
Prophase
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Which stage of the cell cycle?
Telophase
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III. Cell Cycle Regulation

• - The timing and rate of cell division varies by
  cell type.

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A. Normal Cell Cycle

• - Cell division is complex, crucial, and highly
  regulated.
• 1. Cyclins and Cyclin-dependent Kinases (CDKs)
• - Various combinations trigger different
  stages of the cell cycle.
• 2. Quality Control Checkpoints
• - Coordinate important events in the cell
  cycle.

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B. Abnormal Cell Cycle Cancer

• - disease in which cells have lost the ability to
  control their own growth

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1. Causes of Cancer

• - due to changes in a gene (mutations) that
  controls cell division

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• - Carcinogens cancer causing agents (asbestos,
  tobacco smoke, dioxin, UV radiation, X rays)

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2. Cancer Genetics

• - More than 1 mutation is required to produce a
  cancer cell.
• - Some genes that lead to cancer (oncogenes)
  can be inherited.

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3. Characteristics of Cancer Cells

• a) Rapid cell division
• b) Undifferentiated cells
• c) Metastasis
• - cells don't stick together and can
  move elsewhere

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C. Apoptosis

• - programmed cell death
• - occurs in worn out cells and during embryonic
  development

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Fate Map of Cell Lineage in C. elegans
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Caenorhabditis elegans Adult crawling
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C. elegans Embryonic Development
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D. Stem Cells

• - unspecialized cells that can differentiate into
  specialized cells

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1. Embryonic Stem Cells

• - Cells from an early embryo that can
  differentiate into any cell type.

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2. Adult Stem Cells

• - Cells found in various tissues that can
  regenerate several types of tissues where they
  are found.

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The End
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C. Apoptosis

• - programmed cell death
• - occurs in worn out cells and during embryonic
  development