Transcript cell cycle pp

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
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Chapter 9 Cell cycle
I can:
Describe the structure of the duplicated
chromosome.
Explain the cell cycle and stages of mitosis.
Identify the stages of mitosis
Explain the role of kinases and cyclin in the
regulation of the cell cycle.
Describe the loss of cell cycle control and
cancer
Figure 9.1
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 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
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Figure 9.2
100 m
200 m
(a) Reproduction
(b) Growth and
development
20 m
(c) Tissue renewal
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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
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Genome = all of a cell’s genetic info (DNA)
 Prokaryote: single, circular chromosome
 Eukaryote: more than one linear
chromosomes
 Eg. Human:46 chromosomes, mouse: 40,
fruit fly: 8
Somatic Cells
Gametes
Body cells
Sex cells (sperm/egg)
Diploid (2n): 2 of
each type of
chromosome
Haploid (n): 1 of each
type of chromosome
Divide by meiosis
Divide by mitosis
Humans: n = 23
Humans: 2n = 46
Each chromosome must be duplicated before cell division
Duplicated chromosome = 2 sister chromatids
attached by a centromere
Figure 9.5-1
Chromosomes
1
Chromosomal
DNA molecules
Centromere
Chromosome
arm
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Figure 9.5-2
Chromosomes
1
Chromosomal
DNA molecules
Centromere
Chromosome
arm
Chromosome duplication
2
Sister
chromatids
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Figure 9.5-3
Chromosomes
1
Chromosomal
DNA molecules
Centromere
Parent cell
Chromosome
arm
Chromosome duplication
2
Sister
chromatids
Two identical
daughter
cells
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Separation of sister
chromatids
3
Chromosomes in Dividing Cells
Duplicated
chromosomes are
called
chromatids &
are held
together by the
centromere
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Called Sister Chromatids
13
 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
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Phases of the Cell Cycle
The mitotic phase alternates with interphase:
G1  S  G2  mitosis  cytokinesis
Interphase (90% of cell cycle)
 G1 Phase: cell grows and carries out normal
functions
 S Phase: duplicates chromosomes
 G2 Phase: prepares for cell division
M Phase (mitotic)
 Mitosis: nucleus divides
 Cytokinesis: cytoplasm divides
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
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 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
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Control of the Cell Cycle
G1 Checkpoint - Check to see if DNA is damaged
G2 Checkpoint - Check to see if DNA is replicated properly
M Checkpoint - spindle assembly checkpoint, check for alignment of chromosomes
Apoptosis - programmed cell death, if any of the checks fail
 Mitosis is conventionally divided into five phases
 Prophase
 Prometaphase
 Metaphase
 Anaphase
 Telophase
 Cytokinesis overlaps the latter stages of mitosis
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Mitosis
 Continuous process with observable structural
features:
 Chromosomes become visible (prophase)
 Alignment at the equator (metaphase)
 Separation of sister chromatids (anaphase)
 Form two daughter cells (telophase & cytokinesis)
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10 m
Figure 9.7a
G2 of Interphase
Centrosomes
(with centriole
pairs)
Nucleolus
Chromosomes Early mitotic
Centromere
(duplicated,
spindle
Aster
uncondensed)
Nuclear
envelope
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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
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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
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Plasma
membrane
Prophase
Early mitotic
Centromere
spindle
Aster
Two sister chromatids of
one chromosome
Figure 9.7d
Prometaphase
Fragments
of nuclear
envelope
Kinetochore
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Metaphase
Nonkinetochore
microtubules
Kinetochore
microtubule
Metaphase
plate
Spindle
Centrosome at
one spindle pole
Figure 9.7e
Telophase and
Cytokinesis
Anaphase
Cleavage
furrow
Daughter
chromosomes
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Nuclear
envelope
forming
Nucleolus
forming
Cytokinesis
 Cytoplasm of cell divided
 Animal Cells: cleavage furrow
 Plant Cells: cell plate forms
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10 m
Figure 9.7f
G2 of Interphase
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10 m
Figure 9.7g
Prophase
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10 m
Figure 9.7h
Prometaphase
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10 m
Figure 9.7i
Metaphase
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10 m
Figure 9.7j
Anaphase
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10 m
Figure 9.7k
Telophase and
Cytokinesis
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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
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 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
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 During prometaphase, some spindle microtubules
attach to the kinetochores of chromosomes and
begin to move the chromosomes
 Kinetochores are protein complexes that are located
on the centromere
 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
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Figure 9.8
Aster
Sister
chromatids
Centrosome
Metaphase plate
(imaginary)
Kinetochores
Microtubules
Chromosomes
Overlapping
nonkinetochore
microtubules Kinetochore
microtubules
1 m
0.5 m
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Centrosome
Figure 9.8a
Microtubules
Chromosomes
1 m
Centrosome
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Figure 9.8b
Kinetochores
Kinetochore
microtubules
0.5 m
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 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
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Figure 9.9
Experiment
Results
Kinetochore
Spindle
pole
Conclusion
Mark
Chromosome
movement
Motor
protein
Chromosome
Microtubule
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Kinetochore
Tubulin
subunits
Figure 9.9a
Experiment
Kinetochore
Spindle
pole
Mark
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Figure 9.9b
Results
Conclusion
Chromosome
movement
Motor
Microtubule
protein
Chromosome
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Kinetochore
Tubulin
subunits
• During anaphase chromosome movement is
correlated with kinetechore microtubules
shortening at their kinetechore ends and not
the spindle pole ends
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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
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Figure 9.10a
(a) Cleavage of an animal cell (SEM)
Cleavage furrow
Contractile ring of
microfilaments
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100 m
Daughter cells
Cytokinesis in animal vs. plant cells
Figure 9.10ba
Vesicles
forming
cell plate
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Wall of parent
cell
1 m
Figure 9.11
Nucleus
Chromosomes
Nucleolus condensing
Chromosomes
10 m
1 Prophase
2 Prometaphase
Cell plate
3 Metaphase
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4 Anaphase
5 Telophase
• mitosis video
• mitosis phases video
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Types of Cell Reproduction
Asexual reproduction involves a
single cell dividing to make 2 new,
identical daughter cells
Mitosis & binary fission are
examples of asexual reproduction
Sexual reproduction involves two
cells (egg & sperm) joining to make a
new cell (zygote) that is NOT
identical to the original cells
Meiosis is an example
50
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
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Figure 9.12-1
Origin of
replication
E. coli cell
1 Chromosome
replication
begins.
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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.
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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.
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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.
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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
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Figure 9.13
Chromosomes
Microtubules
Intact nuclear
envelope
(a) Dinoflagellates
Kinetochore
microtubule
Intact nuclear
envelope
(b) Diatoms and some yeasts
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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
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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.
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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
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Figure 9.15
G1 checkpoint
Control
system
G1
M
G2
M checkpoint
G2 checkpoint
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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
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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
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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
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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
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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
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 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
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 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
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Figure 9.17-1
Scalpels
1 A sample of
human connective
tissue is cut
up into small
pieces.
Petri
dish
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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
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With PDGF
Cultured fibroblasts
(SEM)
10 m
Figure 9.17a
Cultured fibroblasts
(SEM)
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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
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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
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20 m
(b) Cancer cells
Figure 9.18a
20 m
(a) Normal mammalian cells
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Figure 9.18b
20 m
(b) Cancer cells
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9.3 The Cell Cycle and Cancer
neoplasm: abnormal growth of cells
benign: non-cancerous
malignant: cancerous
Cancer: cellular growth disorder that results from the mutation of
genes that regulate the cell cycle
Cancer cells
●lack differentiation
●have abnormal nuclei
●form tumors
●undergo metastasis
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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
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 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
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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.
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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.
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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.
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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)
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 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
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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)
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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
Test your Understanding # 6 p 190
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Ch. 9 Understanding Check
What is the correct phase of the cell cycle/mitosis for
the following:
A. Most cells that no longer divide or rarely divide are
in this phase
B. Sister chromatids separate and move apart
C. Mitotic spindle begins to form
D. Cell plate or cleavage furrow form
E. Chromosomes replicate
F. Chromosomes line up on equatorial plate
G. Nuclear membrane forms
H. Chromosomes become visible
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Ch 9 Understanding check
1.
2.
3.
4.
Compare sexual to asexual reproduction.
Compare/contrast mitosis to meiosis.
Describe the events of meiosis.
Define: genome, gametes, chromatin, chromosome,
centromere, kinetochore, checkpoint, Cdk, MPF
5. What is the longest part of the cell cycle? Why?
6. If the diploid number is 46, what is the haploid
number?
7. At the end of mitosis and cytokinesis, how do
daughter cells compare with their parent cell when it
was in G1?
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Understanding Check
1. A cell’s DNA was measured at 5 picograms. DNA
levels range from 3-6 pgms in the cell cycle . What
stage of the cell cycle is this cell in. How do you
know?
2. At metaphase, if the haploid number is 3, how many
chromatids does this cell have?
3. How do we know the cell uses chemical signals?
4. Summarize the cell control system.
5. Compare a cancer cell to a normal cell. What goes
wrong?
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More Check
1. How do we know the cell uses chemical signals?
2. Summarize the cell control system.
3. Compare a cancer cell to a normal cell. What goes
wrong?
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Test Yourself
over Mitosis
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94
Mitosis Quiz
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95
Mitosis quiz answers
•
•
•
•
•
•
•
•
•
•
A.-centrioles
k.-nuclear envelope fragments
B.- asters
l. –nonkinetechore microtubules
C.- chromatin
m.-chromosome
D.- nucleolus
n.-centriole
E.- nuclear envelope
o.- kinetechore microtubules
F.- plasma membrane
G.-spindle microtubules (kinetechore microtubules)
H.-centrioles
I.-centromere/kinetechore
J.-chromatid
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Mitosis Quiz
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97
•
•
•
•
•
•
P.- spindle
Q.-metaphase plate(equator)
R. daughter chromosomes
S. cleavage furrow
T.- nucleus forming
U.- nuclear envelope forming
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Name the Stages of Mitosis:
Early Anaphase
Early prophase
Metaphase
Interphase
Late
Prophase
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Late telophase,
Mid-Prophase
Advanced
cytokinesis
Early
Telophase,
Begin
cytokinesis
Late
Anaphase
Locate the Four Mitotic
Stages in Plants
Anaphase
Telophase
Metaphase
Prophase
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• cell division bozeman
• cell cycle interactive
• cell cycle animations
• Cell cycle game
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