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Biology
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10-2 Cell Division
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10-2 Cell Division
Cell Division
In prokaryotes, cell division is matter of separating
the contents of the cell into 2 or more parts.
In eukaryotes, cell division is more complex and
occurs in two major stages.
Two main stage of cell division:
Mitosis
Cytokinesis
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10-2 Cell Division
The first stage, division of the cell nucleus, is
called mitosis.
The second stage, division of the cell cytoplasm, is
called cytokinesis.
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10-2 Cell Division
Chromosomes
Chromosomes
•In eukaryotes, genetic information is carried by
chromosomes.
•Chromosomes are made up of DNA and proteins.
•Cells have a specific number of chromosomes.
Example:
Fruit Flies
8 chromosomes
Humans
46 chromosomes
Carrots
18 chromosomes
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10-2 Cell Division
Chromosomes
•Each chromosome
consists of two identical
“sister” chromatids.
Sister chromatids
•Each pair of chromatids
is attached at an area
called the centromere.
•When the cell divides,
the sister chromatids
separate.
Centromere
•One chromatid goes to
each of the new cells.
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10-2 Cell Division
The Cell Cycle
What are the main events of the cell
cycle?
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10-2 Cell Division
The Cell Cycle
Cell Cycle
The cell cycle is the series of events that cells go
through as they grow and divide.
Interphase is the period of growth that occurs
between cell divisions.
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10-2 Cell Division
The Cell Cycle
During the cell cycle:
• a cell grows
• prepares for division
• divides to form two daughter cells, each
of which begins the cycle again
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10-2 Cell Division
The Cell Cycle
The cell cycle consists of four phases:
• G1 (First Gap Phase)
• S Phase
• G2 (Second Gap Phase)
• M Phase
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10-2 Cell Division
Events of the Cell Cycle
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10-2 Cell Division
Events of the Cell Cycle
Events of the Cell Cycle
During G1, the cell
• increases in size
• synthesizes new proteins and organelles
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10-2 Cell Division
Events of the Cell Cycle
During the S phase,
• chromosomes are replicated
• DNA synthesis takes place
Once a cell enters the S phase, it usually completes
the rest of the cell cycle.
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10-2 Cell Division
Events of the Cell Cycle
The G2 Phase (Second Gap Phase)
• organelles and molecules required for cell
division are produced
• Once G2 is complete, the cell is ready to start the
M phase—Mitosis
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10-2 Cell Division
Mitosis
What are the four phases of mitosis?
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10-2 Cell Division
Events of the Cell Cycle
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10-2 Cell Division
Mitosis
Mitosis
Biologists divide the events of mitosis
into four phases:
• Prophase
• Metaphase
• Anaphase
• Telophase
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10-2 Cell Division
Mitosis
Mitosis
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10-2 Cell Division
Mitosis
Section 10-2
Spindle
forming
Prophase
Prophase
Chromosomes
(paired
chromatids)
Centromere
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10-2 Cell Division
Mitosis
Spindle
forming
Prophase
Prophase is the first and
longest phase of mitosis.
The centrioles separate
and take up positions on
opposite sides of the
nucleus.
Centromere
Chromosomes
(paired
chromatids)
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10-2 Cell Division
Mitosis
The centrioles lie in a
region called the
centrosome.
The centrosome helps
to organize the spindle,
a fanlike microtubule
structure that helps
separate the
chromosomes.
Spindle
forming
Centromere
Chromosomes
(paired
chromatids)
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10-2 Cell Division
Mitosis
Spindle
forming
Chromatin condenses
into chromosomes.
The centrioles separate
and a spindle begins to
form.
The nuclear envelope
breaks down.
Centromere
Chromosomes
(paired
chromatids)
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10-2 Cell Division
Mitosis
Metaphase
Centriole
Spindle
Centriole
Metaphase
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10-2 Cell Division
Mitosis
Centriole
Metaphase
The second phase of
mitosis is metaphase.
The chromosomes line
up across the center of
the cell.
Microtubules connect
the centromere of each
chromosome to the
poles of the spindle.
Spindle
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10-2 Cell Division
Mitosis
Anaphase
Individual
chromosomes
Anaphase
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10-2 Cell Division
Mitosis
Anaphase
Individual
chromosomes
Anaphase is the third
phase of mitosis.
The sister chromatids
separate into individual
chromosomes.
The chromosomes
continue to move until
they have separated into
two groups.
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10-2 Cell Division
Mitosis
Telophase
Nuclear
envelope
reforming
Telophase
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10-2 Cell Division
Mitosis
Telophase
Telophase is the
fourth and final phase
of mitosis.
Chromosomes gather
at opposite ends of the
cell and lose their
distinct shape.
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10-2 Cell Division
Mitosis
A new nuclear envelope
forms around each cluster
of chromosomes.
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10-2 Cell Division
Cytokinesis
Cytokinesis
Cytokinesis
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10-2 Cell Division
Cytokinesis
During cytokinesis, the
cytoplasm pinches in
half.
Each daughter cell has
an identical set of
duplicate chromosomes
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10-2 Cell Division
Cytokinesis in Plants
In plants, a structure known as the cell plate forms
midway between the divided nuclei.
Cell plate
Cell wall
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10-2 Cell Division
Cytokinesis in Plants
The cell plate gradually develops into a separating
membrane.
A cell wall then begins to appear in the cell plate.
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10-2
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10-2
The series of events that cells go through as
they grow and divide is called
a. the cell cycle.
b. mitosis.
c. interphase.
d. cytokinesis.
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10-2
The phase of mitosis during which the
chromosomes line up across the center of the
cell is
a. prophase.
b. metaphase.
c. anaphase.
d. telophase.
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10-2
Cytokinesis usually occurs
a. at the same time as telophase.
b. after telophase.
c. during interphase.
d. during anaphase
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10-2
DNA replication takes place during the
a. S phase of the cell cycle.
b. G1 phase of the cell cycle.
c. G2 phase of the cell cycle.
d. M phase of the cell cycle.
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10-2
During mitosis, “sister” chromatids separate from
one another during
a. telophase.
b. interphase.
c. anaphase.
d. metaphase.
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