1. LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 12
The Cell Cycle
Lectures by
Erin Barley
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.

2. Overview: The Key Roles of Cell Division
• The ability of
organisms to
produce more of
their own kind best
distinguishes living
things from
nonliving matter
• The continuity of
life is based on the
reproduction of
cells, or cell
division
• “Every cell from a
cell” (Virchow, 1855).
© 2011 Pearson Education, Inc.
Figure 12.1 How do a cell’s chromosomes change during cell division?

3. • 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
© 2011 Pearson Education, Inc.

4. Figure 12.2 The functions of cell division.
100 µm
(a) Reproduction
200 µm
(b) Growth and
development
20 µm
(c) Tissue renewal

5. Concept 12.1: Most cell division results in
genetically identical daughter cells
• Most cell division results in daughter cells with
identical genetic information, DNA
• The exception is meiosis, a special type of division
that can produce sperm and egg cells
© 2011 Pearson Education, Inc.

6. 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
© 2011 Pearson Education, Inc.
Figure 12.3 Eukaryotic chromosomes.
20 µm

7. • Eukaryotic chromosomes consist of
chromatin, a complex of DNA and
protein that condenses during cell
division
• Every eukaryotic species has a
characteristic number of
chromosomes in each cell nucleus
• Somatic cells (nonreproductive cells)
have two sets of chromosomes
• Gametes (reproductive cells: sperm
and eggs) have half as many
chromosomes as somatic cells
© 2011 Pearson Education, Inc.

8. 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
(joined copies of the original chromosome), which separate
during cell division
• The centromere is the narrow “waist” of the duplicated
chromosome, where the two chromatids are most closely
attached
Figure 12.4 A highly condensed, duplicated human chromosome (SEM).
Sister
chromatids
Cohesins
© 2011 Pearson Education, Inc.
Centromere
0.5 µm

9. Figure 12.5 Chromosome duplication and distribution during cell division.
Chromosomal
DNA molecules
Chromosomes
• During cell
division, the two
sister
chromatids of
each duplicated
chromosome
separate and
move into two
nuclei
• Once separate,
the chromatids
are called
chromosomes
© 2011 Pearson Education, Inc.
1
Centromere
Chromosome
arm
Chromosome duplication
(including DNA replication)
and condensation
2
Sister
chromatids
Separation of sister
chromatids into
two chromosomes
3

10. • Eukaryotic cell division consists of
– Mitosis, the division of the genetic material in the
nucleus
– Cytokinesis, the division of the cytoplasm
• Gametes are produced by a variation of cell
division called meiosis
– Meiosis yields nonidentical daughter cells that
have only one set of chromosomes, half as many
as the parent cell
© 2011 Pearson Education, Inc.

11. Concept 12.2: The mitotic phase alternates
with interphase in the cell cycle
• Walther Flemming, the German anatomist, was
responsible for the discovery of mitosis and
cytokinesis, which refers to cell division.
– He used aniline dyes to isolate from the gills and fins
of salamanders a substance that he called
"chromatin”
• In 1882, his results on the stages of mitosis were
published in a book entitled, "Cell Substance,
Nucleus and Cell Division”
• Based on his research, Flemming concluded that
each cell's nuclei comes from another cell nucleus.
© 2011 Pearson Education, Inc.

12. Phases of the Cell Cycle
• The cell cycle consists of:
–Mitotic (M) phase -mitosis and cytokinesis
• Mitosis is conventionally divided into five phases:
– Prophase, Prometaphase, Metaphase, Anaphase and Telophase
• Cytokinesis overlaps the latter stages of mitosis
–Interphase -cell growth and copying of chromosomes in
preparation for cell division (about 90% of the cell cycle)
Figure 12.6 The cell cycle.
– G1 phase (“first gap”)
– S phase (“synthesis”)
– G2 phase (“second gap”)
INTERPHASE
M
o
yt
MIT C
(M) OTIC
P
sis
ne
ki
sis
• The cell grows during all three
phases, but chromosomes are
duplicated only during the S phase
HAS
BioFlix: Mitosis
© 2011 Pearson Education, Inc.
S
(DNA synthesis)
G1
ito
• Can be divided into subphases:
E
G2

13. 10 µm
Figure 12.7 Exploring: Mitosis in an Animal Cell
G2 of Interphase
Centrosomes
(with centriole pairs)
Nucleolus
Chromatin
(duplicated)
Nuclear
envelope
Plasma
membrane
Prophase
Early mitotic
spindle
Aster
Centromere
Chromosome, consisting
of two sister chromatids
Prometaphase
Fragments
of nuclear
envelope
Kinetochore
Metaphase
Nonkinetochore
microtubules
Kinetochore
microtubule
Anaphase
Metaphase
plate
Spindle
Centrosome at
one spindle pole
Telophase and Cytokinesis
Cleavage
furrow
Daughter
chromosomes
Nuclear
envelope
forming
Nucleolus
forming

14. Figure 12.7 Exploring: Mitosis in an Animal Cell
G2 of Interphase
Centrosomes
(with centriole
pairs)
Chromatin
(duplicated)
Prophase
Early mitotic
spindle
Plasma
membrane
Nucleolus
Nuclear
envelope
• A nuclear envelope
encloses the nucleus
• Nucleolus (nucleoli) are
visible
• Centrosome (two centroles)
duplicated, therefore two
centrosomes
• Duplicated chromosomes
have not yet condensed
Aster
Centromere
Chromosome, consisting
of two sister chromatids
• Chromatin is condensing into
chromosomes
• Nucleolus (nucleoli) disappear
• Duplicated chromosomes
appear as two identical sister
chromatids
• Mitotic spindle begins to form,
see asters
• Centrosome move away from
each other
Prometaphase
Fragments
of nuclear
envelope
Kinetochore
Nonkinetochore
microtubules
Kinetochore
microtubule
• Nuclear envelope fragments
• Microtubules from centrosomes
invade nuclear area
• Chromosomes more condensed,
have kinetochores
• Microtubules attach to
kinetochores, become
‘kinetochores microtubules’
• Nonkinetochores microtubules
interact with those of opposite pole
of spindle

15. Figure 12.7 Exploring: Mitosis in an Animal Cell
Metaphase
Metaphase
plate
Spindle
Centrosome at
one spindle pole
• Centrosomes at opposite poles
of the cells
• Chromosomes convened at
metaphase plate, centromere lie
at the metaphase plate
• For each chromosome, the
kinetochores of the sister
chromatids are attach
to,kinetochores microtubules
coming from opposite poles.
Anaphase
Telophase and Cytokinesis
Cleavage
furrow
Nucleolus
forming
Nuclear
Daughter
envelope
chromosomes
forming
• Shortest stage of mitosis
• Two daughter nuclei. Nuclear
• Sister chromatids of each pair
envelope arise.
• Nucleolus (nucleoli) reappear
separate (each one now is a
• Chromosomes are less
chromosome)
• Kinetochores microtubules
condensed
• Remaining spindle microtubules
shorten and chromosomes
move toward opposite ends of
are depolymerized.
• Mitosis, the nucleus division into
the cell
• Nonkinetochores microtubules
two identical nuclei is complete
lengthen and the cell elongates --------------------------------------------• End of anaphase, two complete • Cytokinesis in animal cells is
equivalent collections of
sinchronized with telophase
chromosomes

16. 10 µm
Figure 12.7 Exploring: Mitosis in an Animal Cell
G2 of Interphase
Prophase
Prometaphase

17. 10 µm
Figure 12.7 Exploring: Mitosis in an Animal Cell
Metaphase
Anaphase
Telophase and Cytokinesis

18. The Mitotic Spindle: A Closer Look
• The mitotic spindle is a structure made of
microtubules that controls chromosome movement
during mitosis
• In animal cells, assembly of spindle microtubules
begins in the centrosome, the microtubule
organizing center
• The centrosome replicates during interphase, forming
two centrosomes that migrate to opposite ends of the
cell during prophase and prometaphase
• An aster (a radial array of short microtubules)
extends from each centrosome
• The spindle includes: the centrosomes, the spindle
microtubules, and the asters
© 2011 Pearson Education, Inc.

19. • During prometaphase, some spindle microtubules attach to
the kinetochores of chromosomes and begin to move the
chromosomes
• Kinetochores are
protein complexes
associated with
centromeres
• At metaphase, the
chromosomes are
all lined up at the
metaphase plate,
an imaginary
structure at the
midway point
between the
spindle’s two poles
Figure 12.8 The mitotic spindle at metaphase.
Aster
Centrosome
Sister
chromatids
Metaphase
plate
(imaginary)
Chromosomes
Kinetochores
Centrosome
1 µm
Overlapping
nonkinetochore
microtubules
Kinetochore
microtubules
0.5 µm
© 2011 Pearson Education, Inc.
Microtubules

20. Figure 12.9 Inquiry: At which end do kinetochore microtubules shorten during anaphase?
• In anaphase, sister
chromatids
separate and move
along the
kinetochore
microtubules
toward opposite
ends of the cell
• The microtubules
shorten by
depolymerizing at
their kinetochore
ends
EXPERIMENT
Kinetochore
Spindle
pole
Mark
RESULTS
CONCLUSION
Chromosome
movement
Microtubule
Motor protein
Chromosome
© 2011 Pearson Education, Inc.
Kinetochore
Tubulin
subunits

21. Figure 12.9 Inquiry: At which end do kinetochore microtubules shorten during anaphase?
CONCLUSION
Microtubule
Chromosome
movement
Motor protein
Chromosome
Kinetochore
Tubulin
subunits

22. • Nonkinetochore microtubules from opposite poles
overlap and push against each other, elongating
the cell
• In telophase, genetically identical daughter nuclei
form at opposite ends of the cell
• Cytokinesis begins during anaphase or telophase
and the spindle eventually disassembles
© 2011 Pearson Education, Inc.

23. Cytokinesis: A Closer Look
• In animal cells, cytokinesis occurs by a process
known as cleavage, forming a cleavage furrow
• In plant cells, a cell plate forms during cytokinesis
Video: Animal Mitosis
Video: Sea Urchin (Time Lapse)
Animation: Cytokinesis
© 2011 Pearson Education, Inc.

24. Figure 12.10 Cytokinesis in animal and plant cells.
(a) Cleavage of an animal cell (SEM)
Cleavage furrow
Contractile ring of
microfilaments
100 µm
(b) Cell plate formation in a plant cell (TEM)
Vesicles
forming
cell plate
Wall of parent cell
Cell plate
1 µm
New cell wall
Daughter cells
Daughter cells

25. Figure 12.10 Cytokinesis in animal and plant cells.
(a) Cleavage of an animal cell (SEM)
Cleavage furrow
Contractile ring of
microfilaments
100 µm
Daughter cells

26. Figure 12.10 Cytokinesis in animal and plant cells.
(b) Cell plate formation in a plant cell (TEM)
Vesicles Wall of parent cell
forming
Cell plate
cell plate
1 µm
New cell wall
Daughter cells

27. Figure 12.11 Mitosis in a plant cell.
Nucleus
Chromatin
condensing
Nucleolus
1 Prophase
Chromosomes
2 Prometaphase 3 Metaphase
Cell plate
4 Anaphase
10 µm
5 Telophase

28. Binary Fission in Bacteria
• 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), and the
two daughter chromosomes actively move apart
• The plasma membrane pinches inward, dividing
the cell into two
© 2011 Pearson Education, Inc.

29. Figure 12.12 Bacterial cell division by binary fission.
Origin of
replication
E. coli cell
1 Chromosome
replication
begins.
2 Replication
continues.
3 Replication
finishes.
4 Two daughter
cells result.
Cell wall
Plasma membrane
Bacterial chromosome
Two copies
of origin
Origin
Origin

30. 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
(a) Bacteria
Bacterial
chromosome
Chromosomes
(b) Dinoflagellates
Microtubules
Intact nuclear
envelope
Kinetochore
microtubule
(c) Diatoms and
some yeasts
Intact nuclear
envelope
Kinetochore
microtubule
(d) Most eukaryotes
Fragments of
nuclear envelope
© 2011 Pearson Education, Inc.
Figure 12.13 Mechanisms of cell division in several groups of organisms.

31. 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 differences result from regulation at the
molecular level
• Cancer cells manage to escape the usual controls
on the cell cycle
© 2011 Pearson Education, Inc.

32. 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
© 2011 Pearson Education, Inc.
EXPERIMENT
Experiment 1
S
Experiment 2
G1
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 G1nucleus immediately
began mitosis—a spindle
formed and chromatin
condensed, even though
the chromosome had not
been duplicated.
Figure 12.14 Inquiry: Do molecular signals in the cytoplasm
regulate the cell cycle?

33. 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
© 2011 Pearson Education, Inc.
G1 checkpoint
Control
system
G1
M
M checkpoint
S
G2
G2 checkpoint
Figure 12.15 Mechanical analogy for the
cell cycle control system.

34. Figure 12.16 The G1 checkpoint.
• For many cells, the G1 checkpoint seems to be the most
important
• 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
G0
G1 checkpoint
G1
(a) Cell receives a go-ahead signal.
© 2011 Pearson Education, Inc.
G1
(b) Cell does not receive ago-ahead signal.

35. The Cell Cycle Clock: Cyclins and CyclinDependent Kinases
• Two types of regulatory proteins are involved in
cell cycle control: cyclins and cyclin-dependent
kinases (Cdks)
• Cdks activity fluctuates during the cell cycle
because it is controled by cyclins, so named
because their concentrations vary with the cell
cycle
• MPF (maturation-promoting factor) is a cyclin-Cdk
complex that triggers a cell’s passage past the G 2
checkpoint into the M phase
© 2011 Pearson Education, Inc.

36. Figure 12.17 Molecular control of the cell cycle at the G2 checkpoint.
M
G1
S G2
M
G1 S
G2
M
G1
MPF activity
Cyclin
concentration
G
S
1
Time
(a) Fluctuation of MPF activity and cyclin concentration
during the cell cycle
Cdk
Cyclin is
degraded
2
M
G
Degraded
cyclin
G2
Cdk
checkpoint
MPF
Cyclin
(b) Molecular mechanisms that help regulate the cell cycle

37. 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
• 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
© 2011 Pearson Education, Inc.

38. Figure 12.18 The effect of platelet-derived growth factor (PDGF) on cell division.
Scalpels
1 A sample of human
connective tissue is
cut up into small
pieces.
2 Enzymes digest
the extracellular
matrix, resulting in
a suspension of
free fibroblasts.
Petri
dish
3 Cells are transferred to
culture vessels.
Without PDGF
4 PDGF is added
to half the
vessels.
With PDGF
10 µm

39. Figure 12.19 Density-dependent inhibition and
anchorage dependence of cell division.
Anchorage dependence
Density-dependent inhibition
Density-dependent inhibition
(a) Normal mammalian cells
© 2011 Pearson Education, Inc.
20 µm
• A clear 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
• Cancer cells exhibit neither
density-dependent inhibition
nor anchorage dependence
(b) Cancer cells
20 µm

40. Loss of Cell Cycle Controls in Cancer Cells
• 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
© 2011 Pearson Education, Inc.

41. • A normal cell is converted to a cancerous cell by a
process called transformation
• Cancer cells that are not eliminated by the
immune system, 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 additional
tumors
© 2011 Pearson Education, Inc.

42. Figure 12.20 The growth and metastasis of a malignant breast tumor.
Tumor
Lymph
vessel
Blood
vessel
Glandular
tissue
Cancer
cell
1 A tumor grows
from a single
cancer cell.
Metastatic
tumor
2 Cancer
cells invade
neighboring
tissue.
3 Cancer cells spread
through lymph and
blood vessels to
other parts of the
body.
4 Cancer cells
may survive
and establish
a new tumor
in another part
of the body.

43. • Recent advances in understanding the cell cycle and cell
cycle signaling have led to advances in cancer treatment
– Intracellular receptors that can trigger cell division
• Herceptin (HER2)- cell-surface receptor tyrosine kinase hormone
treatment
• Estrogen Receptor (ER) treated with Tamoxifen
Figure 12.21 Impact: Advances in Treatment of Breast Cancer
© 2011 Pearson Education, Inc.

44. Figure 12.UN01
INTERPHASE
G1
S
Cytokinesis
G2
Mitosis
MITOTIC (M) PHASE
Prophase
Telophase and
Cytokinesis
Prometaphase
Anaphase
Metaphase

45. Figure 12.UN02

46. Figure 12.UN03

47. Figure 12.UN04

48. Figure 12.UN05

49. Figure 12.UN06