Download Ch9 Slides - Mrs. Brenner`s Biology

Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 9
The Cell Cycle and
Cellular
Reproduction
Lecture Outline
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Outline
•
•
•
•
9.1 The Cell Cycle
9.2 Mitosis and Cytokinesis
9.3 The Cell Cycle and Cancer
9.4 Prokaryotic Cell Division
2
9.1 The Cell Cycle
• The cell cycle is an orderly set of stages
from the first division to the time the
resulting daughter cells divide
• Just prior to the next division:
 The cell grows larger
 The number of organelles doubles
 The DNA is replicated
• The two major stages of the cell cycle:
 Interphase (includes several stages)
 Mitotic Stage (includes mitosis and cytokinesis)
3
The Cell Cycle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Interphase
G1 checkpoint
Cell cycle main checkpoint.
If DNA is damaged, apoptosis
will occur. Otherwise, the cell
is committed to divide when
growth signals are present
and nutrients are available.
S
(growth and DNA
replication)
G1
G0
G1
(growth)
M
G2
(growth and final
preparations for
G2
division)
G2 checkpoint
Mitosis checkpoint.
Mitosis will occur
if DNA has
replicated properly.
Apoptosis will
occur if the DNA is
damaged and
cannot be repaired.
M
M checkpoint
Spindle assembly
checkpoint. Mitosis
will not continue if
chromosomes are
not properly aligned.
4
The Cell Cycle
• Interphase
 Most of the cell cycle is spent in
interphase
 Cell performs its usual functions
 Time spent in interphase varies by cell
type
 Nerve and muscle cells do not
complete the cell cycle (remain in the
G0 stage)
5
The Cell Cycle
• Interphase consists of: G1, S, and G2 phases
 G1 Phase:
•
•
•
•
Recovery from previous division
Cell doubles its organelles
Cell grows in size
Cell accumulates raw materials for DNA synthesis
•
•
•
•
DNA replication
Proteins associated with DNA are synthesized
Chromosomes enter with 1 chromatid each
Chromosomes leave with 2 identical chromatids (sister
chromatids) each
 S Phase:
 G2 Phase:
• Between DNA replication and onset of mitosis
• Cell synthesizes proteins necessary for division
6
The Cell Cycle
• M (Mitotic) Stage
 Includes:
• Mitosis
– Nuclear division
– Daughter chromosomes are distributed by the mitotic
spindle to two daughter nuclei
• Cytokinesis
– Division of the cytoplasm
 Results in two genetically identical daughter
cells
7
The Cell Cycle
• The cell cycle is controlled by internal and
external signals
• A signal is a molecule that either stimulates or
inhibits a metabolic event.
 Internal signals
• Family of proteins called cyclins that increase and
decrease as the cell cycle continues
• Without cyclins, the cell cycle stops at G1, M or G2
(checkpoints)
• Allows time for any damage to be repaired
8
The Cell Cycle
• Apoptosis is programmed cell death
• It involves a sequence of cellular events:
 fragmenting of the nucleus,
 blistering of the plasma membrane
 engulfing of cell fragments.
• Apoptosis is caused by enzymes called
caspases.
• Mitosis and apoptosis are opposing forces
 Mitosis increases cell number
 Apoptosis decreases cell number
9
Apoptosis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
apoptotic cell
blebs
Cell rounds
up, and nucleus
collapses.
Chromatin
condenses, and
nucleus fragments.
Plasma membrane
blisters, and blebs
form.
DNA
fragment
Cell fragments
contain DNA
fragments.
cell
fragment
Courtesy Douglas R. Green/LaJolla Institute for Allergy and Immunology
10
The Cell Cycle
• Apoptosis
 Cells harbor caspases that are kept in
check by inhibitors
• Can be unleashed by internal or external
signals
 Signal protein p53
• Stops the cell cycle at G1 when DNA is
damaged
• Initiates an attempt at DNA repair
–If successful, the cycle continues to
mitosis
–If not, apoptosis is initiated
11
Regulation at the G1
Checkpoint
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
CDK
not present
CDK present
E2F binds to DNA.
P
P
RB
E2F
protein
E2F not released
E2F
RB
E2F
protein
released
E2F
phosphorylated RB
DNA
cell cycle
proteins
a.
no DNA
damage
breakdown
of p53
p53
DNA
damage
P
P
P
P
p53 binds to DNA.
DNA
DNA
phosphorylated p53
DNA repair
proteins
apoptosis
b.
12
9.2 Mitosis and Cytokinesis
• DNA is in very long threads




Chromosomes
Stretched out and intertwined between divisions
DNA is associated with histones (proteins)
DNA and histone proteins are collectively called
chromatin
• Before mitosis begins:
 Chromatin condenses (coils) into distinctly
visible chromosomes
 Each species has a characteristic
chromosome number
13
Diploid Chromosome Numbers of
Some Eukaryotes
14
Mitosis and Cytokinesis
• The diploid (2n) number includes two sets
of chromosomes of each type
 Humans have 23 different types of
chromosomes
• Each type is represented twice in each body cell
(diploid)
• Only sperm and eggs have one of each type
·termed haploid (n)
 The haploid (n) number for humans is 23
• Two representatives of each chromosome type
• Makes a total of 2n = 46 in each nucleus
– One set of 23 from individual’s father (paternal)
– Other set of 23 from individual’s mother (maternal)
15
Mitosis and Cytokinesis
• At the end of S phase:
 Each chromosome internally duplicated
 Consists of two identical DNA chains
• Sister chromatids (two strands of genetically identical
chromosomes)
• Attached together at a single point (called centromere)
• During mitosis:
 Centromeres holding sister chromatids together
separate
 Sister chromatids separate
 Each becomes a daughter chromosome
 Sisters of each type are distributed to opposite
daughter nuclei
16
Duplicated Chromosomes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
sister chromatids
centromere
kinetochore
a.
9,850
b.
one chromatid
© Andrew Syred/Photo Researchers, Inc.
17
Mitosis and Cytokinesis
• Just outside the nucleus is the centrosome
 This is the microtubule organizing center in animal
cells
 Organizes the mitotic spindle
• Contains many fibers
• Each fiber is composed of a bundle of microtubules
 In animals, the centrosome contains two barrelshaped centrioles
• Oriented at right angles to each other within the centrosome
• Each has 9 triplets of microtubules arranged in a cylinder
• Centrosome was also replicated in S-phase, so
there are two centrosomes before mitosis begins
18
Mitosis and Cytokinesis
• Phases of Mitosis:
 Prophase
• Chromatin has condensed
– Chromosomes are distinguishable with microscope
– Each chromosome has two sister chromatids attached at
the centromere
•
•
•
•
•
Nucleolus disappears
Nuclear envelope disintegrates
Spindle begins to assemble
The two centrosomes move away from each other
Microtubules form star-like arrays termed asters
19
Mitosis and Cytokinesis
• Phases of Mitosis
 Prometaphase
• The centromere of each chromosome
develops two kinetochores
– Specialized protein complex
– One attached to each sister chromatid
» Physically connect sister chromatids with specialized
microtubules (kinetochores)
» These connect sister chromatids to opposite poles of
the mother cell
20
Mitosis and Cytokinesis
• Stages of Mitosis
 Metaphase
• Chromosomes are pulled around by kinetochore fibers
• Forced to align across the equatorial plane of the cell
– Metaphase plate - Represents plane through which
mother cell will be divided
 Anaphase
• Centromere dissolves, releasing sister chromatids
• Sister chromatids separate
– Now called daughter chromosomes
– Pulled to opposite poles along kinetochore fibers
21
Mitosis and Cytokinesis
• Stages of Mitosis
 Telophase
• Spindle disappears
• Now two clusters of daughter chromosomes
– Still two of each type with all types represented
– Clusters are incipient daughter nuclei
• Nuclear envelopes form around the two
incipient daughter nuclei
– Each daughter nucleus receives one chromosome of
each type
22
Mitosis and Cytokinesis
• Cytokinesis = division of cytoplasm
• Allocates the mother cell’s cytoplasm equally to
daughter nucleus
• Encloses each daughter cell in its own plasma
membrane
• Often begins in anaphase
• Animal cytokinesis:




A cleavage furrow appears between daughter nuclei
Formed by a contractile ring of actin filaments
Like pulling on a drawstring
Eventually pinches the mother cell in two
23
Mitosis and Cytokinesis
• Cytokinesis in plant cells begins with the formation of a
cell plate
 Rigid cell walls outside plasma membrane do not
permit furrowing
 Many small membrane-bounded vesicles
 Eventually fuse into one thin vesicle extending across
the mother cell
 The membranes of the cell plate become the plasma
membrane between the daughter cells
 The space between the daughter cells becomes filled
with the middle lamella
 Daughter cells later secrete primary cell walls on
opposite sides of the middle lamella
24
Cytokinesis in Animal Cells
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
X 4,000
Cleavage furrow
Contractile ring
X 4,000
25
(top): © Thomas Deerinck/Visuals Unlimited; (bottom): © SPL/Getty RF
Cytokinesis in Plant Cells
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
daughter cells
cell plate formation
daughter nucleus
vesicles containing
membrane components
fusing to form cell plate
nucleoli
daughter
nucleus
(left): © B.A. Palevitz and E.H. Newcomb/BPS/Tom Stack & Associates
26
Phases of Mitosis in Animal and
Plant Cells
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
centrosome
has centrioles
Animal Cell
at Interphase
aster
duplicated
chromosome
20 µm
20 µm
spindle
pole
MITOSIS
nuclear
envelope
fragments
chromosomes at
metaphase plate
9 µm
centromere
daughter chromosome
20µm
cleavage furrow
16µm
kinetochore
nucleolus
chromatin
condenses
nucleolus
disappears
kinetochore
spindle fiber
spindle
fibers forming
polar spindle fiber
centrosome
20µm
Early Prophase
Centrosomes have duplicated.
Chromatin is condensing into
chromosomes, and the nuclear
envelope is fragmenting.
Prophase
Nucleolus has disappeared, and
duplicated chromosomes are visible.
Centrosomes begin moving apart,
and spindle is in process of forming.
Prophase
Nucleolus has disappeared, and
duplicated chromosomes are visible.
Centrosomes begin moving apart,
and spindle is in process of forming.
kinetochore
spindle fiber
Metaphase
Anaphase
Centromeres of duplicated chromosomes
Sister chromatids part and become daughter
are aligned at the metaphase plate (center
chromosomes that move toward the spindle
of fully formed spindle). Kinetochore spindle
poles. In this way, each pole receives the same
fibers attached to the sister chromatids
number and kinds of chromosomes as the parent cell.
come from opposite spindle poles.
Telophase
Daughter cells are forming
as nuclear envelopes and
nucleoli reappear. Chromosomes will
become indistinct chromatin.
lacks centrioles
Plant Cell
at Interphase
25µm
cell wall
chromosomes
6.2µm
spindle pole lacks
centrioles and aster
20µm
spindle fibers
6.2µm
6.2µm
cell plate
6.6µm
Animal cell(Early prophase, Prophase, Metaphase, Anaphase, Telophase): © Ed Reschke; Animal cell(Prometaphase): © Michael Abbey/Photo Researchers, Inc.;
Plant cell(Early prophase, Prometaphse): © Ed Reschke; Plant cell(Prophase, Metaphase, Anaphase): © R. Calentine/Visuals Unlimited; Plant cell(Telophase): © Jack M.
Bostrack/Visuals Unlimited;
27
Phases of Mitosis in Animal and Plant Cells
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
centrosome
has centrioles
Animal Cell
at Interphase
aster
20 µm
MITOSIS
nuclear
envelope
fragments
Early Prophase
Centrosomes have duplicated.
chromatin
condenses
Chromatin is condensing into
nucleolus
disappears
chromosomes, and the nuclear
envelope is fragmenting.
Early Prophase
centrosome
lacks centrioles
Plant Cell
at Interphase
25 µm
Animal cell(Early prophase): © Ed Reschke; Plant cell(Early prophase): © Ed Reschke
Phases of Mitosis in Animal and Plant Cells
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
centrosome
has centrioles
Animal Cell
at Interphase
aster
20 µm
duplicated
chromosome
Prophase
nuclear
envelope
fragments
MITOSIS
20 µm
centromere
Nucleolus has disappeared, and
duplicated chromosomes are
chromatin
condenses
visible. Centrosomes begin moving
nucleolus
disappears
spindle
fibers forming
Early Prophase
Centrosomes have duplicated.
Chromatin is condensing into
chromosomes, and the nuclear
envelope is fragmenting.
apart, and spindle is in process
of forming.
Prophase
centrosome
lacks centrioles
Plant Cell
at Interphase
25 µm
cell wall chromosomes
6.2 µm
Animal cell(Early prophase, Prophase): © Ed Reschke; Plant cell(Early prophase): © Ed Reschke; Plant cell(Prophase): © R. Cal entine/Visuals Unlimited
Phases of Mitosis in Animal and Plant Cells
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
centrosome
has centrioles
Animal Cell
at Interphase
aster
20 µm
duplicated
chromosome
MITOSIS
nuclear
envelope
fragments
20 µm
spindle
pole
9 µm
kinetochore
Prometaphase
centromere
The kinetochore of each
chromatid is attached to a
chromatin
condenses
nucleolus
disappears
kinetochore spindle fiber. Polar
spindle
fibers forming
kinetochore
spindle fiber
spindle fibers stretch from each
polar spindle fiber
Early Prophase
Centrosomes have duplicated.
Chromatin is condensing into
chromosomes, and the nuclear
envelope is fragmenting.
Prophase
Nucleolus has disappeared, and
duplicated chromosomes are visible.
Centrosomes begin moving apart,
and spindle is in process of forming.
spindle pole and overlap.
Prometaphase
centrosome
lacks centrioles
Plant Cell
at Interphase
25 µm
cell wall chromosomes
6.2 µm
spindle pole lacks
centrioles and aster
20 µm
Animal cell(Early prophase, Prophase, Metaphase): © Ed Reschke; Animal cell(Prometaphase): © Michael Abbey/Photo Researchers, Inc.;
Plant cell(Early prophase, Prometaphse): © Ed Reschke; Plant cell(Prophase): © R. Calentine/Visuals Unlimited
Phases of Mitosis in Animal and Plant Cells
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
centrosome
has centrioles
Metaphase
Animal Cell
at Interphase
aster
20 µm
duplicated
chromosome
nuclear
envelope
fragments
20 µm
spindle
pole
9 µm
chromosomes at
metaphase plate
Centromeres of duplicated
20 µm
chromosomes are aligned at the
kinetochore
centromere
MITOSIS
metaphase plate (center of fully
chromatin
condenses
nucleolus
disappears
formed spindle). Kinetochore
spindle
fibers forming
kinetochore
spindle fiber
kinetochore
spindle fiber
sister chromatids come from
polar spindle fiber
Early Prophase
Centrosomes have duplicated.
Chromatin is condensing into
chromosomes, and the nuclear
envelope is fragmenting.
Prophase
Nucleolus has disappeared, and
duplicated chromosomes are visible.
Centrosomes begin moving apart,
and spindle is in process of forming.
Prometaphase
The kinetochore of each chromatid is
attached to a kinetochore spindle fiber.
Polar spindle fibers stretch from each
spindle pole and overlap.
Metaphase
opposite spindle poles.
centrosome
lacks centrioles
Plant Cell
at Interphase
25 µm
cell wall chromosomes
6.2 µm
spindle pole lacks
centrioles and aster
20 µm
spindle fibers attached to the
spindle fibers
6.2 µm
Animal cell(Early prophase, Prophase, Metaphase): © Ed Reschke; Animal cell(Prometaphase): © Michael Abbey/Photo Researchers, Inc.;
Plant cell(Early prophase, Prometaphse): © Ed Reschke; Plant cell(Prophase, Metaphase): © R. Calentine/Visuals Unlimited
Phases of Mitosis in Animal and Plant Cells
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
centrosome
has centrioles
Animal Cell
at Interphase
aster
20 µm
duplicated
chromosome
MITOSIS
nuclear
envelope
fragments
20 µm
spindle
pole
9 µm
chromosomes at
metaphase plate
20 µm
daughter chromosome
20 µm
Sister chromatids part and become
kinetochore
centromere
daughter chromosomes that move
toward the spindle poles. In this
chromatin
condenses
way, each pole receives the same
nucleolus
disappears
kinetochore
spindle fiber
spindle
fibers forming
polar spindle fiber
Early Prophase
Centrosomes have duplicated.
Chromatin is condensing into
chromosomes, and the nuclear
envelope is fragmenting.
Prophase
Nucleolus has disappeared, and
duplicated chromosomes are visible.
Centrosomes begin moving apart,
and spindle is in process of forming.
number and kinds of chromosomes
kinetochore
spindle fiber
Prometaphase
The kinetochore of each chromatid is
attached to a kinetochore spindle fiber.
Polar spindle fibers stretch from each
spindle pole and overlap.
Metaphase
Centromeres of duplicated chromosomes
are aligned at the metaphase plate (center
of fully formed spindle). Kinetochore spindle
fibers attached to the sister chromatids
come from opposite spindle poles.
as the parent cell.
Anaphase
centrosome
lacks centrioles
Plant Cell
at Interphase
Anaphase
25 µm
cell wall
chromosomes
6.2 µm
spindle pole lacks
centrioles and aster
20 µm
spindle fibers
6.2 µm
Animal cell(Early prophase, Prophase, Metaphase, Anaphase): © Ed Reschke; Animal cell(Prometaphase): © Michael Abbey/Photo Researchers, Inc.;
Plant cell(Early prophase, Prometaphse): © Ed Reschke; Plant cell(Prophase, Metaphase, Anaphase): © R. Calentine/Visuals Unlimited
6.2 µm
Phases of Mitosis in Animal and Plant Cells
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
centrosome
has centrioles
Animal Cell
at Interphase
aster
20 µm
duplicated
chromosome
MITOSIS
nuclear
envelope
fragments
20 µm
spindle
pole
9 µm
chromosomes at 20 µm
metaphase plate
daughter chromosome
20 µm
cleavage furrow
16 µm
Telophase
kinetochore
centromere
nucleolus
Daughter cells are forming
as nuclear envelopes and
chromatin
condenses
nucleolus
disappears
kinetochore
spindle fiber
spindle
fibers forming
Early Prophase
Centrosomes have duplicated.
Chromatin is condensing into
chromosomes, and the nuclear
envelope is fragmenting.
nucleoli reappear.
kinetochore
spindle fiber
polar spindle fiber
Metaphase
Anaphase
Prophase
Prometaphase
Centromeres of duplicated chromosomes
Sister chromatids part and become daughter
Nucleolus has disappeared, and
The kinetochore of each chromatid is
chromosomes that move toward the spindle
duplicated chromosomes are visible. attached to a kinetochore spindle fiber. are aligned at the metaphase plate (center
poles. In this way, each pole receives the same
Centrosomes begin moving apart,
Polar spindle fibers stretch from each of fully formed spindle). Kinetochore spindle
fibers attached to the sister chromatids number and kinds of chromosomes as the parent cell.
and spindle is in process of forming.
spindle pole and overlap.
come from opposite spindle poles.
Chromosomes will
Telophase
become indistinct chromatin.
centrosome
lacks centrioles
Plant Cell
at Interphase
25 µm
cell wall chromosomes
6.2 µm
spindle pole lacks
centrioles and aster
20 µm
spindle fibers
6.2 µm
6.2 µm
cell plate
6.6 µm
Animal cell(Early prophase, Prophase, Metaphase, Anaphase, Telophase): © Ed Reschke; Animal cell(Prometaphase): © Michael Abbey/Photo Researchers, Inc.; Plant cell(Early prophase, Prometaphse):
© Ed Reschke; Plant cell(Prophase, Metaphase, Anaphase): © R. Calentine/Visuals Unlimited; Plant cell(Telophase): © Jack M. Bostrack/Visuals Unlimited;
Phases of Mitosis in Animal
and Plant Cells
•
Functions of mitosis:


Permits growth and repair.
In flowering plants, meristematic tissue
retains the ability to divide throughout the
life of the plant
In mammals, mitosis is necessary when:

•
•
•
A fertilized egg becomes an embryo
An embryo becomes a fetus
A cut heals or a broken bone mends
34
Phases of Mitosis in Animal
and Plant Cells
•
Stem Cells

Many mammalian organs contain stem cells
•
•


Retain the ability to divide
Red bone marrow stem cells divide to produce various
types of blood cells
Therapeutic cloning to produce human tissues
can begin with either adult stem cells or embryonic
stem cells
Embryonic stem cells can be used for reproductive
cloning, the production of a new individual
35
Reproductive and Therapeutic
Cloning
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
remove and
discard egg
nucleus
egg
remove
Go nucleus
fuse egg
with Go
nucleus
Go cells from
animal to be
cloned
culture
embryonic
stem cells
a. Reproductive cloning
remove and
discard egg
nucleus
egg
Implant
embryo
into
surrogate
mother
Clone is born
nervous
remove
Go nucleus
Go somatic cells
fuse egg
with Go
nucleus
blood
culture
embryonic
stem cells
muscle
b. Therapeutic cloning
36
9.3 The Cell Cycle and Cancer
• Abnormal growth of cells is called a tumor
 Benign tumors are not cancerous
• Encapsulated
• Do not invade neighboring tissue or spread
 Malignant tumors are cancerous
•
•
•
•
Not encapsulated
Readily invade neighboring tissues
May also detach and lodge in distant places (metastasis)
Results from mutation of genes regulating the cell cycle
• Development of cancer
 Tends to be gradual
 May take years before a cell is obviously cancerous
37
The Cell Cycle and Cancer
• Characteristics of Cancer Cells
 Lack differentiation
• Are non-specialized
• Are immortal (can enter cell cycle repeatedly)
 Have abnormal nuclei
• May be enlarged
• May have abnormal number of chromosomes
• Often have extra copies of genes
 Do not undergo apoptosis
• Normally, cells with damaged DNA undergo apoptosis
• The immune system can also recognize abnormal cells and
trigger apoptosis
• Cancer cells are abnormal but fail to undergo apoptosis
38
The Cell Cycle and Cancer
• Characteristics of Cancer Cells
 Form tumors
• Mitosis is normally controlled by contact with
neighboring cells – contact inhibition
• Cancer cells have lost contact inhibition
 Undergo metastasis
• Original tumor easily fragments
• New tumors appear in other organs
 Undergo angiogenesis
• Formation of new blood vessels
– Brings nutrients and oxygen to the tumor
39
Progression of Cancer
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
New mutations arise, and one cell (brown) has the ability to start a tumor.
primary tumor
lymphatic
vessel
blood
vessel
Cancer in situ. The tumor is at its place of origin. One cell (purple)
mutates further.
lymphatic
vessel
blood
vessel
Cancer cells now have the ability to invade lymphatic and blood vessels
and travel throughout the body.
New metastatic tumors are found some distance from the primary tumor.
40
Cancer Cells vs. Normal Cells
41
The Cell Cycle and Cancer
• Origin of Cancer
 Oncogenes
• Proto-oncogenes promote the cell cycle in
various ways
• If a proto-oncogene is mutated, it may become an
oncogene
 Tumor suppressor genes inhibit the cell
cycle in various ways
• If a tumor suppressor gene becomes inactive, it
may promote cancer development
 Both proto-oncogenes and tumor suppressor
genes are normally regulated in coordination
with organism’s growth plan
42
The Cell Cycle and Cancer
• Origin of Cancer
 Chromosomes normally have special material
at each end called telomeres
 These get shorter each cell division
 When they get very short, the cell will no
longer divide
 Telomerase is an enzyme that maintains the
length of telomeres
 Mutations in telomerase gene:
• Cause telomeres to continue to lengthen, which
• Allows cancer cells to continually divide
43
Causes of
Cancer
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Heredity
growth
factor
growth factor
Activates signaling
proteins in a stimulatory
pathway that extends
to the nucleus.
receptor
protein
Pesticides
and
herbicides
P
signaling
protein
b. Effect of growth factor
oncogene
activated
signaling
protein
Stimulatory
pathway
phosphate
Viruses
a. Influences that cause mutated proto-oncogenes
(called oncogenes) and mutated tumor
suppressor genes
P
P
Radiation
sources
gene product
promotes
cell cycle
Inhibitory
pathway
gene product
inhibits
cell cycle
proto-oncogene
Codes for a growth factor,
a receptor protein, or a
signaling protein in a
stimulatory pathway.
If a proto-oncogene
becomes an oncogene,
the end result can be
active cell division.
c. Stimulatory pathway and
inhibitory pathway
tumor suppressor gene
Codes for a signaling
protein in an inhibitory
pathway. If a tumor
suppressor gene mutates,
the end result can be
active cell division.
d. Cancerous skin cell
1,100X
d: © Biophoto Associates/Photo Researchers, Inc.
44
9.4 Prokaryotic Cell Division
• The prokaryotic chromosome is a ring of DNA




Folded up in an area called the nucleoid
1,000 X the length of cell
Replicated into two rings prior to cell division
Replicated rings attach to the plasma membrane
• Binary fission
 Splitting in two
 Two replicate chromosomes are distributed to two
daughter cells
 Produces two daughter cells identical to original cell –
asexual reproduction
45
Binary Fission
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
chromosome
1. Attachment of chromosome to
a special plasma membrane
site indicates that this
bacterium is about to divide.
cell wall
plasma
membrane
cytoplasm
© Dennis Kunkel Microscopy, Inc./Visuals Unlimited
SEM 2,345X
46
Binary Fission
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
chromosome
1. Attachment of chromosome to
a special plasma membrane
site indicates that this
bacterium is about to divide.
cell wall
plasma
membrane
cytoplasm
2. The cell is preparing for binary
fission by enlarging its cell wall,
plasma membrane, and overall
volume.
© Dennis Kunkel Microscopy, Inc./Visuals Unlimited
SEM 2,345X
47
Binary Fission
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
chromosome
1. Attachment of chromosome to
a special plasma membrane
site indicates that this
bacterium is about to divide.
cell wall
plasma
membrane
cytoplasm
2. The cell is preparing for binary
fission by enlarging its cell wall,
plasma membrane, and overall
volume.
3. DNA replication has produced
two identical chromosomes.
Cell wall and plasma membrane
begin to grow inward.
© Dennis Kunkel Microscopy, Inc./Visuals Unlimited
SEM 2,345X
48
Binary Fission
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
chromosome
1. Attachment of chromosome to
a special plasma membrane
site indicates that this
bacterium is about to divide.
cell wall
plasma
membrane
cytoplasm
2. The cell is preparing for binary
fission by enlarging its cell wall,
plasma membrane, and overall
volume.
3. DNA replication has produced
two identical chromosomes.
Cell wall and plasma membrane
begin to grow inward.
4. As the cell elongates, the
chromosomes are pulled apart.
Cytoplasm is being distributed
evenly.
© Dennis Kunkel Microscopy, Inc./Visuals Unlimited
SEM 2,345X
49
Binary Fission
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
chromosome
1. Attachment of chromosome to
a special plasma membrane
site indicates that this
bacterium is about to divide.
cell wall
plasma
membrane
cytoplasm
2. The cell is preparing for binary
fission by enlarging its cell wall,
plasma membrane, and overall
volume.
3. DNA replication has produced
two identical chromosomes.
Cell wall and plasma membrane
begin to grow inward.
4. As the cell elongates, the
chromosomes are pulled apart.
Cytoplasm is being distributed
evenly.
5. New cell wall and plasma
membrane has divided the
daughter cells.
© Dennis Kunkel Microscopy, Inc./Visuals Unlimited
SEM 2,345X
50
Functions of Cell Division
51