The Continuity of Life: How Cells Reproduce Chapter 10

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The Continuity of Life How Cells Reproduce
Chapter 10
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Cell division is required for growth and
development

• Cell division is the process by which one cell
  gives rise to two or more daughter cells.
• Prokaryotic cells divide by binary fission.
• Eukaryotic cells divide by mitotic cell division.
• Reproductive cells (ex. ova/sperm) are produced
  by meiotic cell division.
• All cells go through a cell cycle during their
  reproduction.
• After cells reproduce they either differentiate
  into specific cell types or they continue to
  divide.

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Mitotic cell division is required for asexual
reproduction
Single celled organisms are able to reproduce
asexually. This occurs when a life form
reproduces 2 genetically identical offspring. In
other words, an organism clones itself.
a) Paramecium, cell division produces two new,
independent organisms.
b) Yeast, a unicellular fungus, reproduces by
cell division.
Fig. 10-1
c) Hydra, a freshwater relative of the sea
anemone, grows a bud on its side. When fully
developed, the bud breaks off and assumes
independent life.
a) Paramecium, cell division produces two new,
independent organisms.
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What occurs during prokaryotic binary fission
(cell division)?

• The prokaryotic cell
• cycle has a long period
• of cell growth followed
• by a rapid cell division.
• This process usually occurs very rapidly.
• E. coli can reproduce every 20 minutes!!!

Fig. 10-2
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The process of binary fission
Step 1 the circular DNA double helix is
attached to the plasma membrane at one point.
Fig. 10-2
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The process of binary fission
Step 2 The DNA replicates and the two DNA double
helices attach to the plasma membrane at nearby
points.
Fig. 10-2
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The process of binary fission
Step 3 New plasma membrane is added between the
attachment points, pushing them further apart.
Fig. 10-2
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The process of binary fission
Step 4 The plasma membrane grows inward at the
middle of the cell.
Fig. 10-2
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The process of binary fission
Step 5 The parent cell divides into two
daughter cells.
Fig. 10-2
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The life cycles of eukaryotic organisms include
both mitotic and meiotic cell division
Fig. 10-4
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What occurs during the eukaryotic cell cycle?

• The eukaryotic cell cycle is divided into 2
  major phases Interphase and Mitotic division.
• There are two types of division in eukaryotic
  cells mitotic cell division and meiotic cell
  division.

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The eukaryotic cell cycle

• Interphase the period of time during which the
  cell grows, replicates its DNA and prepares for
  division.
• 2. Mitotic division - the period of time when the
  cell undergoes nuclear division.

Fig. 10-3
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DNA is organized into chromosomes in eukaryotic
cells.

• Eukaryotic chromosomes consist of DNA bound to
  proteins.
• Remember that a single chromosome contains many
  genes.

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How does DNA in eukaryotic cells organize during
the cell cycle?

• Chromosomes replicate themselves during the DNA
  synthesis phase of the cell cycle.
• Chromosomes then condense during the mitotic
  phase of the cell cycle.
• Sister chromatids are duplicated chromosomes
  joined at the centromere.

Fig. 10-5
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How does mitotic cell division produce
genetically identical daughter cells?

• Step 1 Mitotically active cells first grow in
  the first part of interphase.
• Step 2 Cells then duplicate their DNA.
• Step 3 Cells continue to grow and the new DNA is
  checked for duplication errors.
• Step 4 Cells enter the mitotic phase which is
  made up of 4 parts.

Fig. 10-3
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How do chromosomes change during the mitotic cell
cycle?
Interphase Chromosomes (blue) are thin and
appear as a mass in the center of the cell. The
spindle microtubules (red) extend outward from
the nucleus to all parts of the cell.
Fig. 10-7
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How do chromosomes change during the mitotic cell
cycle?
Prophase The chromosomes (blue) have condensed
and are attached to the spindle microtubules
(red).
Fig. 10-7
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How do chromosomes change during the mitotic cell
cycle?
Metaphase The chromosomes have moved to the
equator of the cell.
Fig. 10-7
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How do chromosomes change during the mitotic cell
cycle?
Anaphase Sister chromatids have separated, and
each set moves toward each pole.
Fig. 10-7
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How do chromosomes change during the mitotic cell
cycle?
Telophase The chromosomes have gathered into
two clusters at either end of the cell. Each
cluster of chromosomes is the site of a future
nucleus. Cytokinesis occurs after the
chromosomes have been separated and are located
at opposite poles of the cell.
Fig. 10-7
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How do chromosomes change during the mitotic cell
cycle?
Resumption of interphase The chromosomes are
relaxing again into a loose state. The spindle
microtubules are disappearing, and the cellular
microtubules of the two new daughter cells are
rearranging into the interphase pattern.
Fig. 10-7
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Cytokinesis in a plant cell
Carbohydrate-filled vesicles bud off the
Golgi complex and move to the equator of the
cell.
Fig. 10-10
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Cytokinesis in a plant cell
The carbohydrate-filled vesicles bud off
the Golgi complex and move to the equator of
the cell.
Fig. 10-10
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Cytokinesis in a plant cell
Vesicles fuse to form a new cell wall (red)
and plasma membrane (yellow) between daughter
cells.
Fig. 10-10
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Cytokinesis in a plant cell
Fig. 10-10
Complete separation of daughter cells.
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How does meiotic cell division produce haploid
cells?

• Meiosis produces four haploid daughter nuclei
  following cell divisions that occur at the end of
  Meiosis I and Meiosis II (2 cell divisions in
  total!)

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Fig. 10-11
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Fig. 10-11
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What are the differences between Mitosis and
Meiosis?
Fig. 10-13
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How does meiotic cell division and sexual
reproduction produce genetic variability?

• Shuffling of homologous chromosomes creates new
• combinations of chromosomes.

See Table 10-1
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How does meiotic cell division and sexual
reproduction produce genetic variability?

• The process of crossing over during Prophase I
  creates chromosomes with new combinations of
  genetic material.
• The fusion of gametes at fertilization creates
  genetically variable offspring.

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Vocabulary ListKnow the following terms
Cell division Daughter cells Binary fission Cell
cycle Differentiate Binary fission Mitosis Meiosis
Mitotic cell division Meiotic cell
division Chromosomes Centromere Chiasmata Crossing
over
Interphase Prophase Metaphase Anaphase Telophase C
ytokinesis Meiosis I Meiosis II