Chapter 8
DNA Replication and Cell Division
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Cells Divide, and Cells Die
Your cells are rapidly dying and
being replaced.
Section 8.1
Cells Divide, and Cells Die
Cell division produces a continuous
supply of replacement cells.
Section 8.1
Cells Divide, and Cells Die
Cell division also has a role in
reproduction, growth, and
development.
Section 8.1
Two Types of Cell Division
Interact in the Sexual Life Cycle
A fertilized egg, or
zygote, divides by
mitosis. The fetus grows
and develops into a
mature adult consisting
of countless cells with
identical DNA.
Section 8.1
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Figure 8.1
Two Types of Cell Division
Interact in the Sexual Life Cycle
Each mature individual
produces sex cells by
another form of cell
division called meiosis.
Section 8.1
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Figure 8.1
Two Types of Cell Division
Interact in the Sexual Life Cycle
Sex cells combine at
fertilization.
Section 8.1
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Figure 8.1
Mitosis Has Many Roles
Mitotic cell divisions allow an organism to grow and develop,
repair tissues, and regenerate lost body parts.
Some organisms reproduce asexually by mitosis.
Section 8.1
Figure 8.2
Cell Death Is Part of Life
Apoptosis, or cell death,
carves out distinctive
structures.
Section 8.1
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Figure 8.3
DNA Replication Precedes Cell Division
For each of the daughter cells
from this division to have
identical DNA, the cell must
first replicate its genome.
Section 8.2
DNA Replication Precedes Cell Division
DNA replication occurs
in multiple steps.
Section 8.2
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Figure 8.4
DNA Replication Precedes Cell Division
Enzymes, such as
helicases, unwind and
hold the DNA apart.
Section 8.2
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Figure 8.4
DNA Replication Precedes Cell Division
Enzymes called
DNA polymerases
create strands that
are complementary
to the original
strands.
Section 8.2
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Figure 8.4
DNA Replication Precedes Cell Division
Ligases form
covalent bonds
between adjacent
nucleotides.
Section 8.2
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Figure 8.4
DNA Replication Precedes Cell Division
After replication, each
DNA molecule has one
parental strand and
one daughter strand.
Section 8.2
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Figure 8.4
Clicker Question #2
The image at right shows a cell’s
DNA before replication. Which of
the following best represents the
position of the newly created (red)
DNA strands after replication is
complete?
A.
B.
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Clicker Question #2
The image at right shows a cell’s
DNA before replication. Which of
the following best represents the
position of the newly created (red)
DNA strands after replication is
complete?
A.
B.
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Prokaryotes Divide by Binary Fission
In prokaryotes,
reproduction occurs by
binary fission, an asexual
process that replicates DNA
and distributes it to two
daughter cells.
Section 8.3
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Figure 8.5
Prokaryotes Divide by Binary Fission
Prokaryotes have one
circular chromosome.
Section 8.3
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Figure 8.5
Prokaryotes Divide by Binary Fission
As the cell prepares to
divide, DNA replicates
and attaches to the
cell membrane.
Section 8.3
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Figure 8.5
Prokaryotes Divide by Binary Fission
The cell membrane
grows between the
two DNA molecules.
Section 8.3
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Figure 8.5
Prokaryotes Divide by Binary Fission
The cell divides in half,
forming two daughter
cells, each identical to
the original.
Section 8.3
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Figure 8.5
Clicker Question #3
Why is binary fission an asexual process?
A. It occurs only in prokaryotes.
B. It does not require DNA replication.
C. It produces two identical cells.
D. The chromosome is circular.
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Clicker Question #3
Why is binary fission an asexual process?
A. It occurs only in prokaryotes.
B. It does not require DNA replication.
C. It produces two identical cells.
D. The chromosome is circular.
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Replicated Chromosomes Condense
Before Cell Division
Eukaryotic cells do not divide
by binary fission. Instead,
they divide by mitosis.
Section 8.4
Figure 8.6
Replicated Chromosomes Condense
Before Cell Division
The DNA in the cell on the
left is loose in the nucleus.
The DNA in the cell on the
right has condensed into
visible chromosomes.
Section 8.4
Figure 8.6
Replicated Chromosomes Condense
Before Cell Division
DNA replication and protein
synthesis occur when DNA is
loosely packed.
Section 8.4
Figure 8.6
Replicated Chromosomes Condense
Before Cell Division
Cell division occurs when
DNA has condensed into
chromosomes.
Section 8.4
Figure 8.6
Replicated Chromosomes Condense
Before Cell Division
Naked DNA wraps
nucleosomes, groups of
histone proteins.
Section 8.4
Figure 8.7
Replicated Chromosomes Condense
Before Cell Division
Before cell division, nucleosomes
cluster together into chromatin.
Scaffold proteins within
chromatin keep it tightly packed.
Section 8.4
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Figure 8.7
Replicated Chromosomes Condense
Before Cell Division
Eventually, discrete chromosomes
form. The highly folded DNA
takes up less space and is easier
to move than unwound
chromatin.
Section 8.4
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Figure 8.7
Mitotic Cell Division Generates
Exact Copies
The cell cycle describes the
events that occur in one
round of cell division.
Section 8.5
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Figure 8.8
Mitotic Cell Division Generates
Exact Copies
During interphase, the cell
replicates its DNA and carries
out many functions unrelated
to cell division.
Section 8.5
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Figure 8.8
Mitotic Cell Division Generates
Exact Copies
During interphase, the cell
replicates its DNA and carries
out many functions unrelated
to cell division.
Section 8.5
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Figure 8.8
Mitotic Cell Division Generates
Exact Copies
During interphase, the cell
replicates its DNA and carries
out many functions unrelated
to cell division.
Section 8.5
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Figure 8.8
Mitotic Cell Division Generates
Exact Copies
During interphase, the cell
replicates its DNA and carries
out many functions unrelated
to cell division.
Section 8.5
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Figure 8.8
Mitotic Cell Division Generates
Exact Copies
Mitosis is the division of the
nucleus, and cytokinesis is
the division of the cell itself.
Section 8.5
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Figure 8.8
Chromosomes Divide During Mitosis
Section 8.5
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Figure 8.9
Chromosomes Divide During Mitosis
Section 8.5
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Figure 8.9
Cytoplasm Splits in Cytokinesis
In an animal cell, the first
sign of cytokinesis is the
cleavage furrow.
Section 8.5
Figure 8.10
Cytoplasm Splits in Cytokinesis
The cleavage furrow
deepens as the ring of
proteins beneath the cell
membrane contracts.
Section 8.5
Figure 8.10
Clicker Question #4
In some fungi and slime molds, mitosis may
occur without cytokinesis. What would you
expect to find in these species?
A. Cells that don’t contain nuclei.
B. Cells that contain multiple nuclei.
C. DNA that never condenses into visible
chromosomes.
D. Nuclei that never enter interphase.
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Clicker Question #4
In some fungi and slime molds, mitosis may
occur without cytokinesis. What would you
expect to find in these species?
A. Cells that don’t contain nuclei.
B. Cells that contain multiple nuclei.
C. DNA that never condenses into visible
chromosomes.
D. Nuclei that never enter interphase.
© 1996 PhotoDisc, Inc./Getty Images/RF
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cancer Arises When Cells Divide
Out of Control
Chemical checkpoints
regulate the cell cycle. But
what if the body loses
control of cell division?
Section 8.6
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Cancer Arises When Cells Divide
Out of Control
A tumor is an abnormal
mass of tissue. The cells of
a tumor divide out of
control. Tumors are either
benign or malignant.
Section 8.6
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Figure 8.11
Cancer Arises When Cells Divide
Out of Control
Genes and the
environment both can
increase cancer risk.
Section 8.6
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Figure 8.12
Cancer Arises When Cells Divide
Out of Control
Cancer treatments include
surgery, drugs (chemotherapy),
and radiation.
Section 8.6
Investigating Life: Cutting Off a Tumor’s
Supply Lines in the War Against Cancer
Tumor cells mutate and divide
quickly, often developing
resistance to drugs.
Section 8.7
Investigating Life: Cutting Off a Tumor’s
Supply Lines in the War Against Cancer
One class of drugs does not
target cancer cells. Instead,
the drugs attack the blood
vessels that supply nutrients
to the tumor.
Section 8.7
Investigating Life: Cutting Off a Tumor’s
Supply Lines in the War Against Cancer
Cells lining blood vessels
divide and accumulate
mutations slowly. Therefore,
blood vessels are less likely
than tumor cells to become
resistant to drugs.
Section 8.7
Investigating Life: Cutting Off a Tumor’s
Supply Lines in the War Against Cancer
Endostatin targets blood
vessel cells. It reduced
tumor growth in mice.
Traditional chemotherapy
drugs delay cancer growth,
but do not prevent it.
Section 8.7
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Figure 8.13