Cellular Division

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Cellular Division

• Mitosis
• Meiosis

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Cell Division

• Necessary for reproduction of a single cell or of
  an entire multicellular organism.
• Two types
• Asexual
• Sexual

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Why a Cell Divides

• Specific issues a cell has
• DNA Overload
• Trouble Exchanging Materials (easier to move
  things short distances than long)
• Surface Area to Volume (too much volume not
  enough surface)

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Asexual Reproduction

• Production of offspring from one parent.
  Cytoplasm, organelles and genetic material are
  identical to the parent cell.

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Sexual Reproduction

• Formation of a new individual from the union of
  two specialized parent cells. Offspring usually
  show some characteristics of each parent.

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Mitosis Asexual Reproduction

• Each daughter cell receives an exact copy of the
  chromosomes present in the parent cell.
• The daughter cells have the same number of
  chromosomes as the parent cell.
• Mitosis involves the duplication of the
  chromosomes, growth of the cytoplasm, and
  division of the nucleus and cytoplasm.

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Cell Cycle
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The Chromosome

• Chromosome- DNA - genetic information
• 46 human chromosomes or 23 pairs
• Sister Chromatids- chromosomes are replicated and
  there are 2 identical parts
• Centromere- point where sister chromatids are
  attached

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Phases of Mitosis

• Interphase (part of cell cycle G1, S, G2 - but
  not mitosis)
• 4 Phase
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis (splitting of the cytoplasm)
• Mitosis is a continuous process in which each
  phase merges into the next.

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Interphase (Cell growth and Preparation for cell
division)

• G1 phase
• Where most cell growth takes place
• Cell increases in size
• Synthesize new proteins and organelles
• S phase
• Chromosomes are replicated here
• DNA and proteins associated
• G2 phase
• Many organelles and molecules required for cell
  division are produced

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ProphaseLongest Phase

• Nuclear Membrane break down and begin to
  disappear
• Centrioles begin moving apart to opposite ends of
  the cell
• Spindle fibers begin to form between the
  centrioles

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PROPHASE
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Metaphase

• Chromosomes are pushed and pulled by the spindle
  fibers and line up along the cells midplane
  (equator).
• The centromere (point where chromatids are
  attached) of each chromosome is attached to a
  separate spindle fiber.
• Chromatid each chromosome consist of two joined
  strands called chromatids each chromatid is a
  duplicate of its partner

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METAPHASE
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Anaphase

• Centromeres divide
• Chromatids separate and move to opposite poles
• The two sets of separated chromosomes move
  through the cytoplasm to opposite ends (poles) of
  the cell.

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ANAPHASE
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ANAPHASE
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Telophase

• Nuclear membrane forms around each group of
  chromosomes
• Chromosomes unwind
• Cytokinesis begins

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Cytokinesis

• The process by which the cytoplasm divides and
  one cell becomes two individual cells. The
  process is different in plants and animals.
• Animals cell pinches inward
• Plants a new cell wall (cell plate) forms
  between the two new cells

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Figure 12.8 Cytokinesis in animal and plant cells
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Figure 12.5x Mitosis
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When cells come into contact with other cells,
they stop growing..
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Effect of Cyclin on the cell cycle Cyclins-
regulate the timing of the cell cycle in
eukaryotic cells
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Somatic Cells(Body cells)

• Humans 46 chromosomes
• Mosquitoes 6 chromosomes
• Goldfish 96 chromosomes
• Corn 20 chromosomes
• Humans have 46 chromosomes in all cells of their
  body (stomach, brain) except the gametes (sex
  cells)
• Diploid number 2n

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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. As a result,
  they form masses of cells called tumors that can
  damage the surrounding tissues.
• Benign vs. malignant tumors benign are
  localized and not spreading malignancies are
  capable of breaking off and starting up in
  another location --
• An astonishing number of cancer cells have a
  defect in a gene called p53, which normally halts
  the cell cycle until all chromosomes have been
  properly replicated. As a result, chromosome
  damage builds up in such cells. This damage
  causes the cells to lose the information needed
  to respond to signals that would normally control
  their growth.

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Types of Cells

• Somatic Cells- regular body cells (skin, muscle,
  etc)
• Diploid (2n)- have two kinds of each chromosome
• Somatic cells undergo mitosis
• Germ Cells- gametes - sex cells
• (sperm and egg)
• Haploid (n)- have one kind of each chromosome.
• Haploid cells will fuse to form a diploid zygote
• Cells undergo meiosis to form germ cells

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Meiosis Sexual Reproduction

• Meiosis does not increase the number of
  chromosomes because gametes have only half the
  number of chromosomes found in somatic cells.
• Gametes of humans have 23 chromosomes
• Haploid number 23n (one half of 46)
• Gametes are formed by Meiosis

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