Transcript cell renewal

CAMPBELL BIOLOGY IN FOCUS
Urry • Cain • Wasserman • Minorsky • Jackson • Reece
9
The Cell Cycle
Lecture Presentations by
Kathleen Fitzpatrick and Nicole Tunbridge
© 2014 Pearson Education, Inc.
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
© 2014 Pearson Education, Inc.
Figure 9.1
© 2014 Pearson Education, Inc.
 In unicellular organisms, division of one cell
reproduces the entire organism
 Cell division enables multicellular eukaryotes to
develop from a single cell and, once fully grown, to
renew, repair, or replace cells as needed
 Cell division is an integral part of the cell cycle, the
life of a cell from formation to its own division
© 2014 Pearson Education, Inc.
Figure 9.2
100 m
200 m
(a) Reproduction
(b) Growth and
development
20 m
(c) Tissue renewal
© 2014 Pearson Education, Inc.
Figure 9.2a
100 m
(a) Reproduction
© 2014 Pearson Education, Inc.
Figure 9.2b
200 m
(b) Growth and development
© 2014 Pearson Education, Inc.
Figure 9.2c
20 m
(c) Tissue renewal
© 2014 Pearson Education, Inc.
Concept 9.1: Most cell division results in
genetically identical daughter cells
 Most cell division results in the distribution of
identical genetic material—DNA—to two daughter
cells
 DNA is passed from one generation of cells to the
next with remarkable fidelity
© 2014 Pearson Education, Inc.
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
© 2014 Pearson Education, Inc.
Figure 9.3
20 m
Eukaryotic chromosomes
© 2014 Pearson Education, Inc.
 Eukaryotic chromosomes consist of chromatin, a
complex of DNA and protein
 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
one set of chromosomes
© 2014 Pearson Education, Inc.
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 identical copies of the original
chromosome
 The centromere is where the two chromatids are
most closely attached
© 2014 Pearson Education, Inc.
Figure 9.4
Sister
chromatids
Centromere
© 2014 Pearson Education, Inc.
0.5 m
 During cell division, the two sister chromatids of each
duplicated chromosome separate and move into two
nuclei
 Once separate, the chromatids are called
chromosomes
© 2014 Pearson Education, Inc.
Figure 9.5-1
Chromosomes
1
Chromosomal
DNA molecules
Centromere
Chromosome
arm
© 2014 Pearson Education, Inc.
Figure 9.5-2
Chromosomes
1
Chromosomal
DNA molecules
Centromere
Chromosome
arm
Chromosome duplication
2
Sister
chromatids
© 2014 Pearson Education, Inc.
Figure 9.5-3
Chromosomes
1
Chromosomal
DNA molecules
Centromere
Chromosome
arm
Chromosome duplication
2
Sister
chromatids
Separation of sister
chromatids
3
© 2014 Pearson Education, Inc.
 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
© 2014 Pearson Education, Inc.
Concept 9.2: 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
© 2014 Pearson Education, Inc.
Phases of the Cell Cycle
 The cell cycle consists of
 Mitotic (M) phase, including mitosis and cytokinesis
 Interphase, including cell growth and copying of
chromosomes in preparation for cell division
© 2014 Pearson Education, Inc.
 Interphase (about 90% of the cell cycle) can be
divided into subphases
 G1 phase (“first gap”)
 S phase (“synthesis”)
 G2 phase (“second gap”)
 The cell grows during all three phases, but
chromosomes are duplicated only during the
S phase
© 2014 Pearson Education, Inc.
Figure 9.6
G1
S
(DNA synthesis)
G2
© 2014 Pearson Education, Inc.
 Mitosis is conventionally divided into five phases
 Prophase
 Prometaphase
 Metaphase
 Anaphase
 Telophase
 Cytokinesis overlaps the latter stages of mitosis
© 2014 Pearson Education, Inc.
Video: Animal Mitosis
Video: Microtubules Mitosis
VIDEO: Mitosis
Video: Microtubules Anaphase
Video: Nuclear Envelope
10 m
Figure 9.7a
G2 of Interphase
Centrosomes
(with centriole
pairs)
Nucleolus
Chromosomes Early mitotic
Centromere
(duplicated,
spindle
Aster
uncondensed)
Nuclear
envelope
© 2014 Pearson Education, Inc.
Prophase
Plasma
membrane
Two sister chromatids of
one chromosome
Prometaphase
Fragments
of nuclear
envelope
Kinetochore
Nonkinetochore
microtubules
Kinetochore
microtubule
10 m
Figure 9.7b
Metaphase
Anaphase
Metaphase
plate
Spindle
Centrosome at
one spindle pole
© 2014 Pearson Education, Inc.
Telophase and
Cytokinesis
Cleavage
furrow
Daughter
chromosomes
Nuclear
envelope
forming
Nucleolus
forming
Figure 9.7c
G2 of Interphase
Centrosomes
(with centriole
pairs)
Chromosomes
(duplicated,
uncondensed)
Nucleolus Nuclear
envelope
© 2014 Pearson Education, Inc.
Plasma
membrane
Prophase
Early mitotic
Centromere
spindle
Aster
Two sister chromatids of
one chromosome
Figure 9.7d
Prometaphase
Fragments
of nuclear
envelope
Kinetochore
© 2014 Pearson Education, Inc.
Metaphase
Nonkinetochore
microtubules
Kinetochore
microtubule
Metaphase
plate
Spindle
Centrosome at
one spindle pole
Figure 9.7e
Telophase and
Cytokinesis
Anaphase
Cleavage
furrow
Daughter
chromosomes
© 2014 Pearson Education, Inc.
Nuclear
envelope
forming
Nucleolus
forming
10 m
Figure 9.7f
G2 of Interphase
© 2014 Pearson Education, Inc.
10 m
Figure 9.7g
Prophase
© 2014 Pearson Education, Inc.
10 m
Figure 9.7h
Prometaphase
© 2014 Pearson Education, Inc.
10 m
Figure 9.7i
Metaphase
© 2014 Pearson Education, Inc.
10 m
Figure 9.7j
Anaphase
© 2014 Pearson Education, Inc.
10 m
Figure 9.7k
Telophase and
Cytokinesis
© 2014 Pearson Education, Inc.
The Mitotic Spindle: A Closer Look
 The mitotic spindle is a structure made of
microtubules and associated proteins
 It controls chromosome movement during mitosis
 In animal cells, assembly of spindle microtubules
begins in the centrosome, the microtubule
organizing center
© 2014 Pearson Education, Inc.
 The centrosome replicates during interphase,
forming two centrosomes that migrate to opposite
ends of the cell during prophase and prometaphase
 An aster (radial array of short microtubules) extends
from each centrosome
 The spindle includes the centrosomes, the spindle
microtubules, and the asters
© 2014 Pearson Education, Inc.
 During prometaphase, some spindle microtubules
attach to the kinetochores of chromosomes and
begin to move the chromosomes
 Kinetochores are protein complexes that assemble
on sections of DNA at centromeres
 At metaphase, the centromeres of all the
chromosomes are at the metaphase plate, an
imaginary structure at the midway point between
the spindle’s two poles
© 2014 Pearson Education, Inc.
Video: Mitosis Spindle
Figure 9.8
Aster
Sister
chromatids
Centrosome
Metaphase plate
(imaginary)
Kinetochores
Microtubules
Chromosomes
Overlapping
nonkinetochore
microtubules Kinetochore
microtubules
1 m
0.5 m
© 2014 Pearson Education, Inc.
Centrosome
Figure 9.8a
Microtubules
Chromosomes
1 m
Centrosome
© 2014 Pearson Education, Inc.
Figure 9.8b
Kinetochores
Kinetochore
microtubules
0.5 m
© 2014 Pearson Education, Inc.
 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
 Chromosomes are also “reeled in” by motor proteins
at spindle poles, and microtubules depolymerize
after they pass by the motor proteins
© 2014 Pearson Education, Inc.
Figure 9.9
Experiment
Results
Kinetochore
Spindle
pole
Conclusion
Mark
Chromosome
movement
Motor
protein
Chromosome
Microtubule
© 2014 Pearson Education, Inc.
Kinetochore
Tubulin
subunits
Figure 9.9a
Experiment
Kinetochore
Spindle
pole
Mark
© 2014 Pearson Education, Inc.
Figure 9.9b
Results
Conclusion
Chromosome
movement
Motor
Microtubule
protein
Chromosome
© 2014 Pearson Education, Inc.
Kinetochore
Tubulin
subunits
 Nonkinetochore microtubules from opposite poles
overlap and push against each other, elongating
the cell
 At the end of anaphase, duplicate groups of
chromosomes have arrived at opposite ends of the
elongated parent cell
 Cytokinesis begins during anaphase or telophase
and the spindle eventually disassembles
© 2014 Pearson Education, Inc.
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
© 2014 Pearson Education, Inc.
© 2014 Pearson Education, Inc.
Animation: Cytokinesis
© 2014 Pearson Education, Inc.
Video: Cytokinesis and Myosin
Figure 9.10
(a) Cleavage of an animal cell (SEM)
Cleavage furrow
Contractile ring of
microfilaments
100 m
(b) Cell plate formation in a plant cell (TEM)
Vesicles
forming
cell plate
Wall of parent
1 m
cell
Cell plate New cell wall
Daughter cells
Daughter cells
© 2014 Pearson Education, Inc.
Figure 9.10a
(a) Cleavage of an animal cell (SEM)
Cleavage furrow
Contractile ring of
microfilaments
© 2014 Pearson Education, Inc.
100 m
Daughter cells
Figure 9.10aa
Cleavage furrow
© 2014 Pearson Education, Inc.
100 m
Figure 9.10b
(b) Cell plate formation in a plant cell (TEM)
Vesicles
forming
cell plate
Wall of parent
1 m
cell
Cell plate New cell wall
Daughter cells
© 2014 Pearson Education, Inc.
Figure 9.10ba
Vesicles
forming
cell plate
© 2014 Pearson Education, Inc.
Wall of parent
cell
1 m
Figure 9.11
Nucleus
Chromosomes
Nucleolus condensing
Chromosomes
10 m
1 Prophase
2 Prometaphase
Cell plate
3 Metaphase
© 2014 Pearson Education, Inc.
4 Anaphase
5 Telophase
Figure 9.11a
Chromosomes
Nucleus
Nucleolus condensing
10 m
1 Prophase
© 2014 Pearson Education, Inc.
Figure 9.11b
Chromosomes
10 m
2 Prometaphase
© 2014 Pearson Education, Inc.
Figure 9.11c
3 Metaphase
© 2014 Pearson Education, Inc.
10 m
Figure 9.11d
4 Anaphase
© 2014 Pearson Education, Inc.
10 m
Figure 9.11e
Cell plate
5 Telophase
© 2014 Pearson Education, Inc.
10 m
Binary Fission in Bacteria
 Prokaryotes (bacteria and archaea) reproduce by a
type of cell division called binary fission
 In E. coli, the single chromosome replicates,
beginning at the origin of replication
 The two daughter chromosomes actively move apart
while the cell elongates
 The plasma membrane pinches inward, dividing the
cell into two
© 2014 Pearson Education, Inc.
Figure 9.12-1
Origin of
replication
E. coli cell
1 Chromosome
replication
begins.
© 2014 Pearson Education, Inc.
Two copies
of origin
Cell wall
Plasma
membrane
Bacterial
chromosome
Figure 9.12-2
Origin of
replication
E. coli cell
1 Chromosome
replication
begins.
2 One copy of the
origin is now at
each end of the
cell.
© 2014 Pearson Education, Inc.
Two copies
of origin
Origin
Cell wall
Plasma
membrane
Bacterial
chromosome
Origin
Figure 9.12-3
Origin of
replication
E. coli cell
1 Chromosome
replication
begins.
2 One copy of the
origin is now at
each end of the
cell.
3 Replication
finishes.
© 2014 Pearson Education, Inc.
Two copies
of origin
Origin
Cell wall
Plasma
membrane
Bacterial
chromosome
Origin
Figure 9.12-4
Origin of
replication
E. coli cell
1 Chromosome
replication
begins.
2 One copy of the
origin is now at
each end of the
cell.
3 Replication
finishes.
4 Two daughter
cells result.
© 2014 Pearson Education, Inc.
Two copies
of origin
Origin
Cell wall
Plasma
membrane
Bacterial
chromosome
Origin
The Evolution of Mitosis
 Since prokaryotes evolved before eukaryotes,
mitosis probably evolved from binary fission
 Certain protists (dinoflagellates, diatoms, and some
yeasts) exhibit types of cell division that seem
intermediate between binary fission and mitosis
© 2014 Pearson Education, Inc.
Figure 9.13
Chromosomes
Microtubules
Intact nuclear
envelope
(a) Dinoflagellates
Kinetochore
microtubule
Intact nuclear
envelope
(b) Diatoms and some yeasts
© 2014 Pearson Education, Inc.
Concept 9.3: 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
© 2014 Pearson Education, Inc.
Evidence for Cytoplasmic Signals
 The cell cycle is driven by specific signaling
molecules present in the cytoplasm
 Some evidence for this hypothesis comes from
experiments with cultured mammalian cells
 Cells at different phases of the cell cycle were fused
to form a single cell with two nuclei at different
stages
 Cytoplasmic signals from one of the cells could
cause the nucleus from the second cell to enter the
“wrong” stage of the cell cycle
© 2014 Pearson Education, Inc.
Figure 9.14
Experiment
Experiment 1
S
G1
Experiment 2
M
G1
Results
S
S
G1 nucleus
immediately entered
S phase and DNA
was synthesized.
M
M
G1 nucleus began
mitosis without
chromosome
duplication.
Conclusion Molecules present in the cytoplasm
control the progression to S and M phases.
© 2014 Pearson Education, Inc.
Checkpoints of 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 timing device of a washing machine
 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
© 2014 Pearson Education, Inc.
Figure 9.15
G1 checkpoint
Control
system
G1
M
G2
M checkpoint
G2 checkpoint
© 2014 Pearson Education, Inc.
S
 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
© 2014 Pearson Education, Inc.
Figure 9.16
G1 checkpoint
G0
G1
G1
Without go-ahead signal,
cell enters G0.
(a) G1 checkpoint
S
M
G1
With go-ahead signal,
cell continues cell cycle.
G2
G1
G1
M G2
M
G2
M checkpoint
Prometaphase
Without full chromosome
attachment, stop signal is
received.
(b) M checkpoint
© 2014 Pearson Education, Inc.
Anaphase
G2
checkpoint
Metaphase
With full chromosome
attachment, go-ahead signal
is received.
Figure 9.16a
G1 checkpoint
G0
G1
Without go-ahead signal,
cell enters G0.
(a) G1 checkpoint
© 2014 Pearson Education, Inc.
G1
With go-ahead signal,
cell continues cell cycle.
Figure 9.16b
G1
G1
M G2
M
G2
M checkpoint
Prometaphase
Without full chromosome
attachment, stop signal is
received.
(b) M checkpoint
© 2014 Pearson Education, Inc.
Anaphase
G2
checkpoint
Metaphase
With full chromosome
attachment, go-ahead signal
is received.
 The cell cycle is regulated by a set of regulatory
proteins and protein complexes including kinases
and proteins called cyclins
© 2014 Pearson Education, Inc.
 An example of an internal signal occurs at the M
phase checkpoint
 In this case, anaphase does not begin if any
kinetochores remain unattached to spindle
microtubules
 Attachment of all of the kinetochores activates a
regulatory complex, which then activates the enzyme
separase
 Separase allows sister chromatids to separate,
triggering the onset of anaphase
© 2014 Pearson Education, Inc.
 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
© 2014 Pearson Education, Inc.
Figure 9.17-1
Scalpels
1 A sample of
human connective
tissue is cut
up into small
pieces.
Petri
dish
© 2014 Pearson Education, Inc.
Figure 9.17-2
Scalpels
1 A sample of
human connective
tissue is cut
up into small
pieces.
Petri
dish
2 Enzymes digest
the extracellular
matrix, resulting
in a suspension of
free fibroblasts.
© 2014 Pearson Education, Inc.
Figure 9.17-3
Scalpels
1 A sample of
human connective
tissue is cut
up into small
pieces.
Petri
dish
2 Enzymes digest
the extracellular
matrix, resulting
in a suspension of
free fibroblasts.
3 Cells are transferred
to culture vessels.
4 PDGF is added to
half the vessels.
© 2014 Pearson Education, Inc.
Figure 9.17-4
Scalpels
1 A sample of
human connective
tissue is cut
up into small
pieces.
Petri
dish
2 Enzymes digest
the extracellular
matrix, resulting
in a suspension of
free fibroblasts.
3 Cells are transferred
to culture vessels.
4 PDGF is added to
half the vessels.
Without PDGF
© 2014 Pearson Education, Inc.
With PDGF
Cultured fibroblasts
(SEM)
10 m
Figure 9.17a
Cultured fibroblasts
(SEM)
© 2014 Pearson Education, Inc.
10 m
 Another example of external signals is densitydependent 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
© 2014 Pearson Education, Inc.
Figure 9.18
Anchorage dependence: cells
require a surface for division
Density-dependent inhibition:
cells form a single layer
Density-dependent inhibition:
cells divide to fill a gap and
then stop
20 m
(a) Normal mammalian cells
© 2014 Pearson Education, Inc.
20 m
(b) Cancer cells
Figure 9.18a
20 m
(a) Normal mammalian cells
© 2014 Pearson Education, Inc.
Figure 9.18b
20 m
(b) Cancer cells
© 2014 Pearson Education, Inc.
Loss of Cell Cycle Controls in Cancer Cells
 Cancer cells do not respond to signals that normally
regulate the cell cycle
 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
© 2014 Pearson Education, Inc.
 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 only 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
© 2014 Pearson Education, Inc.
5 m
Figure 9.19
Breast cancer cell
(colorized SEM)
Lymph
vessel
Metastatic
tumor
Tumor
Blood
vessel
Cancer
cell
Glandular
tissue
1 A tumor grows
from a single
cancer cell.
© 2014 Pearson Education, Inc.
2 Cancer cells
invade
neighboring
tissue.
3 Cancer cells spread
through lymph and
blood vessels to
other parts of the
body.
4 A small percentage
of cancer cells may
metastasize to
another part of the
body.
Figure 9.19a
Tumor
Glandular
tissue
1 A tumor grows
from a single
cancer cell.
© 2014 Pearson Education, Inc.
2 Cancer cells
invade
neighboring
tissue.
3 Cancer cells spread
through lymph and
blood vessels to
other parts of the
body.
Figure 9.19b
Lymph
vessel
Metastatic
tumor
Blood
vessel
Cancer
cell
3 Cancer cells spread
through lymph and
blood vessels to
other parts of the
body.
© 2014 Pearson Education, Inc.
4 A small percentage
of cancer cells may
metastasize to
another part of the
body.
5 m
Figure 9.19c
Breast cancer cell
(colorized SEM)
© 2014 Pearson Education, Inc.
 Recent advances in understanding the cell cycle
and cell cycle signaling have led to advances in
cancer treatment
 Medical treatments for cancer are becoming more
“personalized” to an individual patient’s tumor
 One of the big lessons in cancer research is how
complex cancer is
© 2014 Pearson Education, Inc.
Figure 9.UN01
Control
200
A B C
Treated
A B C
Number of cells
160
120
80
40
0
0
200
400
600
0
200
400
600
Amount of fluorescence per cell (fluorescence units)
© 2014 Pearson Education, Inc.
Figure 9.UN02
G1
S
Cytokinesis
Mitosis
G2
MITOTIC (M) PHASE
Prophase
Telophase and
Cytokinesis
Prometaphase
Anaphase
Metaphase
© 2014 Pearson Education, Inc.
Figure 9.UN03
© 2014 Pearson Education, Inc.