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Chapter 12
The Cell Cycle
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cellular Growth
Ratio of Surface Area to Volume
Cellular Growth
 As the cell grows, its volume
increases much more rapidly than
the surface area.
 The cell might have difficulty supplying
nutrients and expelling enough waste
products.
Cellular Growth
Transport of Substances
 Substances move by diffusion or by
motor proteins.
 Diffusion over large distances is
slow and inefficient.
 Small cells maintain more efficient
transport systems.
Cellular Growth
Cellular Communications
 The need for signaling proteins to
move throughout the cell also limits
cell size.
 Cell size affects the ability of the cell
to communicate instructions for
cellular functions.
Cellular Growth
The Cell Cycle
 Cell division prevents the cell from
becoming too large.
 It also is the way the cell reproduces so
that you grow and heal certain injuries.
 Cells reproduce by a cycle of growing
and dividing called the cell cycle.
In unicellular organisms, division of one cell
reproduces the entire organism
Multicellular organisms depend on cell
division for:
Development from a fertilized cell
Growth
Repair
Cell division is an integral part of the cell
cycle, the life of a cell from formation to its
own division
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 12-2a
100 µm
(a) Reproduction
Fig. 12-2b
200 µm
(b) Growth and development
Fig. 12-2c
20 µm
(c) Tissue renewal
Concept 12.1: Cell division results in
genetically identical daughter cells
 Most cell division results in daughter cells with identical genetic
information, DNA
 A special type of division produces nonidentical daughter cells
(gametes, or sperm and egg cells)
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cellular Organization of the Genetic
Material
 All the DNA in a cell constitutes the cell’s genome
 A genome can consist of a single DNA molecule (common in
prokaryotic cells) or a number of DNA molecules (common in
eukaryotic cells)
 DNA molecules in a cell are packaged into chromosomes
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 12-3
chromatin
20 µm
 Every eukaryotic species has a characteristic number of
chromosomes in each cell nucleus
 Somatic cells (nonreproductive cells) have two sets of
chromosomes (diploid number)
 Gametes (reproductive cells: sperm and eggs) have half as many
chromosomes as somatic cells (haploid number)
 Eukaryotic chromosomes consist of chromatin, a complex of DNA
and protein that condenses during cell division
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Distribution of Chromosomes During
Eukaryotic Cell Division
 In preparation for cell division, DNA is replicated and the
chromosomes condense
 Each duplicated chromosome has two sister chromatids, which
separate during cell division
 The centromere is the narrow “waist” of the duplicated
chromosome, where the two chromatids are most closely attached
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 12-4
0.5 µm
Chromosomes
Chromosome arm
DNA molecules
Chromosome
duplication
(including DNA
synthesis)
Centromere
Sister
chromatids
Separation of
sister chromatids
Centromere
Sister chromatids
Cellular Growth
 Interphase is the stage during which
the cell grows, carries out cellular
functions, and replicates.
 Mitosis is the stage of the cell cycle
during which the cell’s nucleus and
nuclear material divide.
 Cytokinesis is the method by which a
cell’s cytoplasm divides, creating a new
cell.
Cellular Growth
The Stages of Interphase
 The first stage of interphase, G1
 The cell is growing, carrying out
normal cell functions, and preparing to
replicate DNA.
Cellular Growth
The Second Stage of Interphase, S
 The cell copies its DNA in
preparation for cell division.
Cellular Growth
The Third Stage of Interphase, G2
 The cell prepares for the division of its
nucleus.
Interphase
occurs before mitosis begins
•
•
Chromosomes are copied (# doubles)
Chromosomes appear as threadlike coils (chromatin) at the start, but
each chromosome and its copy(sister chromosome) change to sister
chromatids at end of this phase
•Nucleus
•CELL
MEMBRANE
•Cytoplasm
Interphase
•Animal
Cell
•Plant Cell
•Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Prophase
1st step in Mitosis
•
Mitosis begins (cell begins to divide)
•
Centrioles (or poles) appear and begin to move to opposite end of the
cell.
•
Spindle fibers form between the poles.
•Sister
chromatids
•Centrioles
•Spindle fibers
 The mitotic spindle is an apparatus of microtubules that
controls chromosome movement during mitosis
 During prophase, assembly of spindle microtubules begins in
the centrosome, the microtubule organizing center
 The centrosome replicates, forming two centrosomes that
migrate to opposite ends of the cell, as spindle microtubules
grow out from them
 An aster (a radial array of short microtubules) extends from each
centrosome
•
The spindle includes the centrosomes, the spindle microtubules, and
the asters
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Prophase
•Animal
Cell
•Plant Cell
•Spindle fibers
•Centrioles
•Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Metaphase
2nd step in Mitosis
•
Chromatids (or pairs of chromosomes) attach to the spindle fibers.
•Centrioles
•Spindle fibers
Metaphase
•Animal
Cell
•Plant Cell
•Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Anaphase
3rd step in Mitosis
•
Chromatids (or pairs of chromosomes) separate and begin to move to
opposite ends of the cell.
•Centrioles
•Spindle fibers
Anaphase
•Animal
Cell
•Plant Cell
•Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Telophase
4th step in Mitosis
•
Two new nuclei form.
•
Chromosomes appear as chromatin (threads rather than rods).
•
Mitosis ends.
•Nuclei
•Chromatin
•Nuclei
Telophase
•Animal
Cell
•Plant Cell
•Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Cytokinesis
occurs after mitosis
•
Cell membrane moves inward to create two daughter cells – each with
its own nucleus with identical chromosomes.
•Animal Mitosis -- Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
•Plant Mitosis -- Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
Concept 12.2: The mitotic phase
alternates with
interphase in the cell cycle
 In 1882, the German anatomist Walther Flemming developed dyes to
observe chromosomes during mitosis and cytokinesis
 Which we already talked about
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 12-8
EXPERIMENT
Kinetochore
Spindle
pole
Mark
RESULTS
CONCLUSION
Chromosome
movement
Kinetochore
Motor
Microtubule protein
Chromosome
Tubulin
subunits
Fig. 12-8a
EXPERIMENT
Kinetochore
Spindle
pole
Mark
RESULTS
Fig. 12-8b
CONCLUSION
Chromosome
movement
Kinetochore
Microtubule
Motor
protein
Chromosome
Tubulin
Subunits
Binary Fission
 Prokaryotes (bacteria and archaea) reproduce by a type of cell
division called binary fission
 In binary fission, the chromosome replicates (beginning at the
origin of replication), the two origins move to opposite sides of the
cell and the two daughter chromosomes actively move apart
 No mitosis is involved
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 12-11-1
Cell wall
Origin of
replication
E. coli cell
Two copies
of origin
Plasma
membrane
Bacterial
chromosome
Fig. 12-11-2
Cell wall
Origin of
replication
E. coli cell
Two copies
of origin
Origin
Plasma
membrane
Bacterial
chromosome
Origin
Fig. 12-11-3
Cell wall
Origin of
replication
E. coli cell
Two copies
of origin
Origin
Plasma
membrane
Bacterial
chromosome
Origin
Fig. 12-11-4
Cell wall
Origin of
replication
E. coli cell
Two copies
of origin
Origin
Plasma
membrane
Bacterial
chromosome
Origin
The Evolution of Mitosis
 Since prokaryotes evolved before eukaryotes, mitosis probably
evolved from binary fission
 Certain protists exhibit types of cell division that seem intermediate
between binary fission and mitosis
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 12-12
Bacterial
chromosome
•Mechanism not known
(a) Bacteria
Chromosomes
•dinoflagellatesCs attach to
Microtubules
•the nuclear
•Membrane; microtubules
Intact nuclear
envelope
(b) Dinoflagellates
•Pass through the nucleus;
•Then cell divides
•Diatoms and yeast
Kinetochore
microtubule
•Microtubules form
•Within the cell (not
Intact nuclear
envelope
•The nucleus into the
•Cytosol like in
(c) Diatoms and yeasts
•flagellates
Kinetochore
microtubule
Fragments of
nuclear envelope
(d) Most eukaryotes
•eukaryotes
Concept 12.3: The eukaryotic cell cycle
is regulated by a molecular control
system
 The frequency of cell division varies with the type of cell
 These cell cycle differences result from regulation at the molecular
level
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Evidence for Cytoplasmic Signals
 The cell cycle appears to be driven by specific chemical signals
present in the cytoplasm
 Some evidence for this hypothesis comes from experiments in which
cultured mammalian cells at different phases of the cell cycle were
fused to form a single cell with two nuclei
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 12-13
EXPERIMENT
Experiment 1
S
G1
Experiment 2
M
G1
RESULTS
S
S
When a cell in the
S phase was fused
with a cell in G1, the G1
nucleus immediately
entered the S
phase—DNA was
synthesized.
M
M
When a cell in the
M phase was fused with
a cell in G1, the G1
nucleus immediately
began mitosis—a
spindle formed and
chromatin condensed,
even though the
chromosome had not
been duplicated.
The Cell Cycle Control System
 The sequential events of the cell cycle are directed by a distinct cell
cycle control system, which is similar to a clock
 The cell cycle control system is regulated by both internal and
external controls
 The clock has specific checkpoints where the cell cycle stops until a
go-ahead signal is received
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cell Cycle Regulation
Normal Cell Cycle
 Different cyclin/CDK
(cyclin-dependent kinases)
combinations signal other
activities, including DNA
replication, protein synthesis,
and nuclear division
throughout the cell cycle.
 MPF (maturation-promoting
factor) is a cyclin-Cdk
complex that triggers a cell’s
passage past the G2
checkpoint into the M phase
Cell Cycle Regulation
Quality Control Checkpoints
 The cell cycle has built-in checkpoints
that monitor the cycle and can stop it if
something goes wrong.
 Spindle checkpoints also have been
identified in mitosis.
•
For many cells, the G1 checkpoint seems to be the most important
one
•
If a cell receives a go-ahead signal at the G1 checkpoint, it will
usually complete the S, G2, and M phases and divide
•
If the cell does not receive the go-ahead signal, it will exit the cycle,
switching into a nondividing state called the G0 phase
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 12-15
G0
G1 checkpoint
G1
(a) Cell receives a go-ahead
signal
G1
(b) Cell does not receive a
go-ahead signal
Stop and Go Signs: Internal and
External Signals at the Checkpoints
 An example of an internal signal is that kinetochores not attached to
spindle microtubules send a molecular signal that delays anaphase
until they all have attached; making sure that the cell doesn’t divide
until it has all its parts
 Some external signals are growth factors, proteins released by
certain cells that stimulate other cells to divide
 For example, platelet-derived growth factor (PDGF) stimulates the
division of human fibroblast cells in culture
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
 Another example of external signals is density-dependent
inhibition, in which crowded cells stop dividing
 Most animal cells also exhibit anchorage dependence, in which
they must be attached to a substratum in order to divide
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 12-19
Anchorage dependence then they will grow
Density-dependent inhibition when the cells touch
Density-dependent inhibition
25 µm
25 µm
(a) Normal mammalian cells
(b) Cancer cells
Loss of Cell Cycle Controls in Cancer
Cells
 Cancer cells exhibit neither
density-dependent inhibition nor
anchorage dependence
 Cancer cells do not respond
normally to the body’s control
mechanisms
 Cancer cells may not need
growth factors to grow and
divide:
 They may make their own
growth factor
 They may convey a growth
factor’s signal without the
presence of the growth factor
 They may have an abnormal cell
cycle control system
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 A normal cell is converted to a cancerous cell by a process called
transformation
 Cancer cells form tumors, masses of abnormal cells within otherwise
normal tissue
 If abnormal cells remain at the original site, the lump is called a
benign tumor
 Malignant tumors invade surrounding tissues and can
metastasize, exporting cancer cells to other parts of the body,
where they may form secondary tumors
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 12-20
Lymph
vessel
Tumor
Blood
vessel
Cancer
cell
Metastatic
tumor
Glandular
tissue
1 A tumor grows
from a single
cancer cell.
2 Cancer cells
invade neighboring tissue.
3 Cancer cells spread
to other parts of
the body.
4 Cancer cells may
survive and
establish a new
tumor in another
part of the body.
You should now be able to:
1.
Describe the structural organization of the prokaryotic genome and
the eukaryotic genome
2.
List the phases of the cell cycle; describe the sequence of events
during each phase
3.
List the phases of mitosis and describe the events characteristic of
each phase
4.
Draw or describe the mitotic spindle, including centrosomes,
kinetochore microtubules, nonkinetochore microtubules, and asters
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
5.
Compare cytokinesis in animals and plants
6.
Describe the process of binary fission in bacteria and explain how
eukaryotic mitosis may have evolved from binary fission
7.
Explain how the abnormal cell division of cancerous cells escapes
normal cell cycle controls
8.
Distinguish between benign, malignant, and metastatic tumors
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings