Chapter 12. The Cell Cycle

Август 2, 2022

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Chapter 12. The Cell Cycle

Содержание

2. Overview: The Key Roles of Cell Division The ability of organisms to reproduce best distinguishes living
3. Fig. 12-1
4. In unicellular organisms, division of one cell reproduces the entire organism Multicellular organisms depend on cell
5. Fig. 12-2 100 µm 200 µm 20 µm (a) Reproduction (b) Growth and development (c) Tissue
6. Fig. 12-2a 100 µm (a) Reproduction
7. Fig. 12-2b 200 µm (b) Growth and development
8. Fig. 12-2c 20 µm (c) Tissue renewal
9. Concept 12.1: Cell division results in genetically identical daughter cells Most cell division results in daughter
10. Cellular Organization of the Genetic Material All the DNA in a cell constitutes the cell’s genome
11. Fig. 12-3 20 µm
12. Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus Somatic cells (nonreproductive
13. Distribution of Chromosomes During Eukaryotic Cell Division In preparation for cell division, DNA is replicated and
14. Fig. 12-4 0.5 µm Chromosomes Chromosome duplication (including DNA synthesis) Chromo- some arm Centromere Sister chromatids
15. Eukaryotic cell division consists of: Mitosis, the division of the nucleus Cytokinesis, the division of the
16. Concept 12.2: The mitotic phase alternates with interphase in the cell cycle In 1882, the German
17. Phases of the Cell Cycle The cell cycle consists of Mitotic (M) phase (mitosis and cytokinesis)
18. Interphase (about 90% of the cell cycle) can be divided into subphases: G1 phase (“first gap”)
19. Fig. 12-5 S (DNA synthesis) MITOTIC (M) PHASE Mitosis Cytokinesis G1 G2 INTERPHASE
20. Mitosis is conventionally divided into five phases: Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis is well underway
21. Fig. 12-6 G2 of Interphase Centrosomes (with centriole pairs) Chromatin (duplicated) Nucleolus Nuclear envelope Plasma membrane
22. Prophase Fig. 12-6a Prometaphase G2 of Interphase
23. Fig. 12-6b Prometaphase Prophase G2 of Interphase Nonkinetochore microtubules Fragments of nuclear envelope Aster Centromere Early
24. Fig. 12-6c Metaphase Anaphase Telophase and Cytokinesis
25. Fig. 12-6d Metaphase Anaphase Telophase and Cytokinesis Cleavage furrow Nucleolus forming Metaphase plate Centrosome at one
26. The Mitotic Spindle: A Closer Look The mitotic spindle is an apparatus of microtubules that controls
27. An aster (a radial array of short microtubules) extends from each centrosome The spindle includes the
28. During prometaphase, some spindle microtubules attach to the kinetochores of chromosomes and begin to move the
29. Fig. 12-7 Microtubules Chromosomes Sister chromatids Aster Metaphase plate Centrosome Kineto- chores Kinetochore microtubules Overlapping nonkinetochore
30. In anaphase, sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the
31. Fig. 12-8 EXPERIMENT Kinetochore RESULTS CONCLUSION Spindle pole Mark Chromosome movement Kinetochore Microtubule Motor protein Chromosome
32. Fig. 12-8a Kinetochore Spindle pole Mark EXPERIMENT RESULTS
33. Fig. 12-8b Kinetochore Microtubule Tubulin Subunits Chromosome Chromosome movement Motor protein CONCLUSION
34. Nonkinetochore microtubules from opposite poles overlap and push against each other, elongating the cell In telophase,
35. Cytokinesis: A Closer Look In animal cells, cytokinesis occurs by a process known as cleavage, forming
36. Video: Sea Urchin (Time Lapse) Video: Animal Mitosis Copyright © 2008 Pearson Education, Inc., publishing as
37. Fig. 12-9 Cleavage furrow 100 µm Contractile ring of microfilaments Daughter cells (a) Cleavage of an
38. Cleavage furrow Fig. 12-9a 100 µm Daughter cells (a) Cleavage of an animal cell (SEM) Contractile
39. Fig. 12-9b Daughter cells (b) Cell plate formation in a plant cell (TEM) Vesicles forming cell
40. Fig. 12-10 Chromatin condensing Metaphase Anaphase Telophase Prometaphase Nucleus Prophase 1 2 3 5 4 Nucleolus
41. Fig. 12-10a Nucleus Prophase 1 Nucleolus Chromatin condensing
42. Fig. 12-10b Prometaphase 2 Chromosomes
43. Fig. 12-10c Metaphase 3
44. Fig. 12-10d Anaphase 4
45. Fig. 12-10e Telophase 5 Cell plate 10 µm
46. Binary Fission Prokaryotes (bacteria and archaea) reproduce by a type of cell division called binary fission
47. Fig. 12-11-1 Origin of replication Two copies of origin E. coli cell Bacterial chromosome Plasma membrane
48. Fig. 12-11-2 Origin of replication Two copies of origin E. coli cell Bacterial chromosome Plasma membrane
49. Fig. 12-11-3 Origin of replication Two copies of origin E. coli cell Bacterial chromosome Plasma membrane
50. Fig. 12-11-4 Origin of replication Two copies of origin E. coli cell Bacterial chromosome Plasma membrane
51. The Evolution of Mitosis Since prokaryotes evolved before eukaryotes, mitosis probably evolved from binary fission Certain
52. Fig. 12-12 (a) Bacteria Bacterial chromosome Chromosomes Microtubules Intact nuclear envelope (b) Dinoflagellates Kinetochore microtubule Intact
53. Fig. 12-12ab Bacterial chromosome Chromosomes Microtubules (a) Bacteria (b) Dinoflagellates Intact nuclear envelope
54. Fig. 12-12cd Kinetochore microtubule (c) Diatoms and yeasts Kinetochore microtubule (d) Most eukaryotes Fragments of nuclear
55. Concept 12.3: The eukaryotic cell cycle is regulated by a molecular control system The frequency of
56. Evidence for Cytoplasmic Signals The cell cycle appears to be driven by specific chemical signals present
57. Fig. 12-13 Experiment 1 Experiment 2 EXPERIMENT RESULTS S G1 M G1 M M S S
58. The Cell Cycle Control System The sequential events of the cell cycle are directed by a
59. Fig. 12-14 S G1 M checkpoint G2 M Control system G1 checkpoint G2 checkpoint
60. For many cells, the G1 checkpoint seems to be the most important one If a cell
61. Fig. 12-15 G1 G0 G1 checkpoint Cell receives a go-ahead signal G1 (b) Cell does not
62. The Cell Cycle Clock: Cyclins and Cyclin-Dependent Kinases Two types of regulatory proteins are involved in
63. Fig. 12-16 Protein kinase activity (– ) % of dividing cells (– ) Time (min) 300
64. Fig. 12-17 M G1 S G2 M G1 S G2 M G1 MPF activity Cyclin concentration
65. Fig. 12-17a Time (a) Fluctuation of MPF activity and cyclin concentration during the cell cycle Cyclin
66. Fig. 12-17b Cyclin is degraded Cdk MPF Cdk M S G1 G2 checkpoint Degraded cyclin Cyclin
67. Stop and Go Signs: Internal and External Signals at the Checkpoints An example of an internal
68. Fig. 12-18 Petri plate Scalpels Cultured fibroblasts Without PDGF cells fail to divide With PDGF cells
69. Another example of external signals is density-dependent inhibition, in which crowded cells stop dividing Most animal
70. Fig. 12-19 Anchorage dependence Density-dependent inhibition Density-dependent inhibition (a) Normal mammalian cells (b) Cancer cells 25
71. Cancer cells exhibit neither density-dependent inhibition nor anchorage dependence Copyright © 2008 Pearson Education, Inc., publishing
72. Loss of Cell Cycle Controls in Cancer Cells Cancer cells do not respond normally to the
73. A normal cell is converted to a cancerous cell by a process called transformation Cancer cells
74. Fig. 12-20 Tumor A tumor grows from a single cancer cell. Glandular tissue Lymph vessel Blood
75. Fig. 12-UN1 Telophase and Cytokinesis Anaphase Metaphase Prometaphase Prophase MITOTIC (M) PHASE Cytokinesis Mitosis S G1
76. Fig. 12-UN2
77. Fig. 12-UN3
78. Fig. 12-UN4
79. Fig. 12-UN5
80. Fig. 12-UN6
81. You should now be able to: Describe the structural organization of the prokaryotic genome and the
83. Скачать презентацию

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Overview: The Key Roles of Cell Division
The ability of organisms to

reproduce 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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Fig. 12-1

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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

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Fig. 12-2
100 µm
200 µm
20 µm
(a) Reproduction
(b) Growth and
development
(c) Tissue renewal

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Fig. 12-2a
100 µm
(a) Reproduction

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Fig. 12-2b
200 µm
(b) Growth and development

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Fig. 12-2c
20 µm
(c) Tissue renewal

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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)

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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

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Fig. 12-3
20 µm

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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
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

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Fig. 12-4
0.5 µm
Chromosomes
Chromosome
duplication
(including DNA
synthesis)
Chromo-
some arm
Centromere
Sister
chromatids
DNA molecules
Separation of
sister chromatids
Centromere
Sister chromatids

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Eukaryotic cell division consists of:
Mitosis, the division of 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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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

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Phases of the Cell Cycle
The cell cycle consists of
Mitotic (M) phase

(mitosis and cytokinesis)
Interphase (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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Fig. 12-5
S
(DNA synthesis)
MITOTIC
(M) PHASE
Mitosis
Cytokinesis
G1
G2
INTERPHASE

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Mitosis is conventionally divided into five phases:
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis is well underway by

late telophase

BioFlix: Mitosis

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Fig. 12-6
G2 of Interphase
Centrosomes
(with centriole
pairs)
Chromatin
(duplicated)
Nucleolus
Nuclear
envelope
Plasma
membrane
Early mitotic
spindle
Aster
Centromere
Chromosome, consisting
of two sister chromatids
Prophase
Prometaphase
Fragments
of

nuclear
envelope

Nonkinetochore
microtubules

Kinetochore

Kinetochore
microtubule

Metaphase

Metaphase
plate

Spindle

Centrosome at
one spindle pole

Anaphase

Daughter
chromosomes

Telophase and Cytokinesis

Cleavage
furrow

Nucleolus
forming

Nuclear
envelope
forming

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Prophase
Fig. 12-6a
Prometaphase
G2 of Interphase

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Fig. 12-6b
Prometaphase
Prophase
G2 of Interphase
Nonkinetochore
microtubules
Fragments
of nuclear
envelope
Aster
Centromere
Early mitotic
spindle
Chromatin
(duplicated)
Centrosomes
(with centriole
pairs)
Nucleolus
Nuclear
envelope
Plasma
membrane
Chromosome, consisting
of two sister chromatids
Kinetochore
Kinetochore
microtubule

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Fig. 12-6c
Metaphase
Anaphase
Telophase and Cytokinesis

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Fig. 12-6d
Metaphase
Anaphase
Telophase and Cytokinesis
Cleavage
furrow
Nucleolus
forming
Metaphase
plate
Centrosome at
one spindle pole
Spindle
Daughter
chromosomes
Nuclear
envelope
forming

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The Mitotic Spindle: A Closer Look
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

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An aster (a 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
At metaphase, the chromosomes are all lined up at the metaphase plate, the midway point between the spindle’s two poles

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Fig. 12-7
Microtubules
Chromosomes
Sister
chromatids
Aster
Metaphase
plate
Centrosome
Kineto-
chores
Kinetochore
microtubules
Overlapping
nonkinetochore
microtubules
Centrosome
1 µm
0.5 µm

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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

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Fig. 12-8
EXPERIMENT
Kinetochore
RESULTS
CONCLUSION
Spindle
pole
Mark
Chromosome
movement
Kinetochore
Microtubule
Motor
protein
Chromosome
Tubulin
subunits

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Fig. 12-8a
Kinetochore
Spindle
pole
Mark
EXPERIMENT
RESULTS

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Fig. 12-8b
Kinetochore
Microtubule
Tubulin
Subunits
Chromosome
Chromosome
movement
Motor
protein
CONCLUSION

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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

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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

Animation: Cytokinesis

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Video: Sea Urchin (Time Lapse)
Video: Animal Mitosis
Copyright © 2008 Pearson Education,

Inc., publishing as Pearson Benjamin Cummings

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Fig. 12-9
Cleavage furrow
100 µm
Contractile ring of
microfilaments
Daughter cells
(a) Cleavage of an animal

cell (SEM)

(b) Cell plate formation in a plant cell (TEM)

Vesicles
forming
cell plate

Wall of
parent cell

Cell plate

Daughter cells

New cell wall

1 µm

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Cleavage furrow
Fig. 12-9a
100 µm
Daughter cells
(a) Cleavage of an animal cell (SEM)
Contractile

ring of
microfilaments

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Fig. 12-9b
Daughter cells
(b) Cell plate formation in a plant cell (TEM)
Vesicles
forming
cell

plate

Wall of
parent cell

New cell wall

Cell plate

1 µm

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Fig. 12-10
Chromatin
condensing
Metaphase
Anaphase
Telophase
Prometaphase
Nucleus
Prophase
1
2
3
5
4
Nucleolus
Chromosomes
Cell plate
10 µm

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Fig. 12-10a
Nucleus
Prophase
1
Nucleolus
Chromatin
condensing

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Fig. 12-10b
Prometaphase
2
Chromosomes

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Fig. 12-10c
Metaphase
3

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Fig. 12-10d
Anaphase
4

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Fig. 12-10e
Telophase
5
Cell plate
10 µm

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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), and the two daughter chromosomes actively move apart

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Fig. 12-11-1
Origin of
replication
Two copies
of origin
E. coli cell
Bacterial
chromosome
Plasma
membrane
Cell wall

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Fig. 12-11-2
Origin of
replication
Two copies
of origin
E. coli cell
Bacterial
chromosome
Plasma
membrane
Cell wall
Origin
Origin

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Fig. 12-11-3
Origin of
replication
Two copies
of origin
E. coli cell
Bacterial
chromosome
Plasma
membrane
Cell wall
Origin
Origin

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Fig. 12-11-4
Origin of
replication
Two copies
of origin
E. coli cell
Bacterial
chromosome
Plasma
membrane
Cell wall
Origin
Origin

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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

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Fig. 12-12
(a) Bacteria
Bacterial
chromosome
Chromosomes
Microtubules
Intact nuclear
envelope
(b) Dinoflagellates
Kinetochore
microtubule
Intact nuclear
envelope
(c) Diatoms and yeasts
Kinetochore
microtubule
Fragments of
nuclear envelope
(d)

Most eukaryotes

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Fig. 12-12ab
Bacterial
chromosome
Chromosomes
Microtubules
(a) Bacteria
(b) Dinoflagellates
Intact nuclear
envelope

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Fig. 12-12cd
Kinetochore
microtubule
(c) Diatoms and yeasts
Kinetochore
microtubule
(d) Most eukaryotes
Fragments of
nuclear envelope
Intact nuclear
envelope

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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

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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

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Fig. 12-13
Experiment 1
Experiment 2
EXPERIMENT
RESULTS
S
G1
M
G1
M
M
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.

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.

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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

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Fig. 12-14
S
G1
M checkpoint
G2
M
Control
system
G1 checkpoint
G2 checkpoint

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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

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Fig. 12-15
G1
G0
G1 checkpoint
Cell receives a go-ahead
signal
G1
(b) Cell does not receive

a
go-ahead signal

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The Cell Cycle Clock: Cyclins and Cyclin-Dependent Kinases
Two types of regulatory

proteins are involved in cell cycle control: cyclins and cyclin-dependent kinases (Cdks)
The activity of cyclins and Cdks fluctuates during 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

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Fig. 12-16
Protein kinase activity (– )
% of dividing cells (– )
Time

(min)

300

200

400

100

500

RESULTS

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Fig. 12-17
M
G1
S
G2
M
G1
S
G2
M
G1
MPF activity
Cyclin
concentration
Time
(a) Fluctuation of MPF activity and cyclin concentration during

the cell cycle

Degraded
cyclin

Cdk

checkpoint

Cyclin is
degraded

Cyclin

MPF

(b) Molecular mechanisms that help regulate the cell cycle

Cyclin accumulation

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Fig. 12-17a
Time
(a) Fluctuation of MPF activity and cyclin concentration during
the

cell cycle

Cyclin
concentration

MPF activity

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Fig. 12-17b
Cyclin is
degraded
Cdk
MPF
Cdk
M
S
G1
G2
checkpoint
Degraded
cyclin
Cyclin
(b) Molecular mechanisms that help regulate the cell cycle
G2
Cyclin

accumulation

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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

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Fig. 12-18
Petri
plate
Scalpels
Cultured fibroblasts
Without PDGF
cells fail to divide
With PDGF
cells prolifer-
ate
10 µm

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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

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Fig. 12-19
Anchorage dependence
Density-dependent inhibition
Density-dependent inhibition
(a) Normal mammalian cells
(b) Cancer cells
25 µm
25

µm

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Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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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

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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

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Fig. 12-20
Tumor
A tumor grows
from a single
cancer cell.
Glandular
tissue
Lymph
vessel
Blood
vessel
Metastatic
tumor
Cancer
cell
Cancer cells
invade neigh-
boring tissue.
Cancer cells

spread
to other parts of
the body.

Cancer cells may
survive and
establish a new
tumor in another
part of the body.

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Fig. 12-UN1
Telophase and
Cytokinesis
Anaphase
Metaphase
Prometaphase
Prophase
MITOTIC (M) PHASE
Cytokinesis
Mitosis
S
G1
G2
INTERPHASE

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Fig. 12-UN2

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Fig. 12-UN3

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Fig. 12-UN4

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Fig. 12-UN5

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Fig. 12-UN6

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You should now be able to:
Describe the structural organization of the

prokaryotic genome and the eukaryotic genome
List the phases of the cell cycle; describe the sequence of events during each phase
List the phases of mitosis and describe the events characteristic of each phase
Draw or describe the mitotic spindle, including centrosomes, kinetochore microtubules, nonkinetochore microtubules, and asters

Chapter 12. The Cell Cycle

Содержание

Overview: The Key Roles of Cell DivisionThe ability of organisms to

Fig. 12-1

In unicellular organisms, division of one cell reproduces the entire organismMulticellular

Fig. 12-2100 µm200 µm20 µm(a) Reproduction(b) Growth and development(c) Tissue renewal

Fig. 12-2a100 µm(a) Reproduction

Fig. 12-2b200 µm(b) Growth and development

Fig. 12-2c20 µm(c) Tissue renewal

Concept 12.1: Cell division results in genetically identical daughter cellsMost cell

Cellular Organization of the Genetic MaterialAll the DNA in a cell

Fig. 12-320 µm

Every eukaryotic species has a characteristic number of chromosomes in each

Distribution of Chromosomes During Eukaryotic Cell DivisionIn preparation for cell division,

Fig. 12-40.5 µmChromosomesChromosomeduplication(including DNAsynthesis)Chromo-some armCentromereSisterchromatidsDNA moleculesSeparation ofsister chromatidsCentromereSister chromatids

Eukaryotic cell division consists of:Mitosis, the division of the nucleusCytokinesis, the

Concept 12.2: The mitotic phase alternates with interphase in the cell cycleIn

Phases of the Cell CycleThe cell cycle consists ofMitotic (M) phase

Interphase (about 90% of the cell cycle) can be divided into

Fig. 12-5S(DNA synthesis)MITOTIC(M) PHASEMitosisCytokinesisG1G2INTERPHASE

Mitosis is conventionally divided into five phases:ProphasePrometaphaseMetaphaseAnaphaseTelophaseCytokinesis is well underway by

Fig. 12-6G2 of InterphaseCentrosomes(with centriolepairs)Chromatin(duplicated)NucleolusNuclearenvelopePlasmamembraneEarly mitoticspindleAsterCentromereChromosome, consisting of two sister chromatidsProphasePrometaphaseFragmentsof

ProphaseFig. 12-6aPrometaphaseG2 of Interphase

Fig. 12-6cMetaphaseAnaphaseTelophase and Cytokinesis

Fig. 12-6dMetaphaseAnaphaseTelophase and CytokinesisCleavagefurrowNucleolusformingMetaphaseplateCentrosome atone spindle poleSpindleDaughterchromosomesNuclearenvelopeforming

The Mitotic Spindle: A Closer LookThe mitotic spindle is an apparatus

An aster (a radial array of short microtubules) extends from each

During prometaphase, some spindle microtubules attach to the kinetochores of chromosomes

Fig. 12-7MicrotubulesChromosomesSisterchromatidsAsterMetaphaseplateCentrosomeKineto-choresKinetochoremicrotubulesOverlappingnonkinetochoremicrotubulesCentrosome1 µm0.5 µm

In anaphase, sister chromatids separate and move along the kinetochore microtubules

Fig. 12-8EXPERIMENTKinetochoreRESULTSCONCLUSIONSpindlepoleMarkChromosomemovementKinetochoreMicrotubuleMotorproteinChromosomeTubulinsubunits

Fig. 12-8aKinetochoreSpindlepoleMarkEXPERIMENTRESULTS

Fig. 12-8bKinetochoreMicrotubuleTubulinSubunitsChromosomeChromosomemovementMotorproteinCONCLUSION

Nonkinetochore microtubules from opposite poles overlap and push against each other,

Cytokinesis: A Closer LookIn animal cells, cytokinesis occurs by a process

Video: Sea Urchin (Time Lapse)Video: Animal MitosisCopyright © 2008 Pearson Education,

Fig. 12-9Cleavage furrow100 µmContractile ring ofmicrofilamentsDaughter cells(a) Cleavage of an animal

Cleavage furrowFig. 12-9a100 µmDaughter cells(a) Cleavage of an animal cell (SEM)Contractile

Fig. 12-9bDaughter cells(b) Cell plate formation in a plant cell (TEM)Vesiclesformingcell

Fig. 12-10ChromatincondensingMetaphaseAnaphaseTelophasePrometaphaseNucleusProphase12354NucleolusChromosomesCell plate10 µm

Fig. 12-10aNucleusProphase1NucleolusChromatincondensing

Fig. 12-10bPrometaphase2Chromosomes

Fig. 12-10cMetaphase3

Fig. 12-10dAnaphase4

Fig. 12-10eTelophase5Cell plate10 µm

Binary FissionProkaryotes (bacteria and archaea) reproduce by a type of cell

Fig. 12-11-1Origin ofreplicationTwo copiesof originE. coli cellBacterialchromosomePlasmamembraneCell wall

Fig. 12-11-2Origin ofreplicationTwo copiesof originE. coli cellBacterialchromosomePlasmamembraneCell wallOriginOrigin

Fig. 12-11-3Origin ofreplicationTwo copiesof originE. coli cellBacterialchromosomePlasmamembraneCell wallOriginOrigin

Fig. 12-11-4Origin ofreplicationTwo copiesof originE. coli cellBacterialchromosomePlasmamembraneCell wallOriginOrigin

The Evolution of MitosisSince prokaryotes evolved before eukaryotes, mitosis probably evolved

Fig. 12-12(a) BacteriaBacterialchromosomeChromosomesMicrotubulesIntact nuclearenvelope(b) DinoflagellatesKinetochoremicrotubuleIntact nuclearenvelope(c) Diatoms and yeastsKinetochoremicrotubuleFragments ofnuclear envelope(d)

Fig. 12-12abBacterialchromosomeChromosomesMicrotubules(a) Bacteria(b) DinoflagellatesIntact nuclearenvelope

Fig. 12-12cdKinetochoremicrotubule(c) Diatoms and yeastsKinetochoremicrotubule(d) Most eukaryotesFragments of nuclear envelopeIntact nuclearenvelope