Download Mitosis - Napa Valley College

4/6/2015
CAMPBELL
BIOLOGY
Outline
TENTH
EDITION
Reece • Urry • Cain • Wasserman • Minorsky • Jackson
12
Cell Cycle - Mitosis
I. Overview
II. Mitotic Phase
I.
II.
III.
IV.
Prophase
Metaphase
Telophase
Cytokinesis
III. Binary fission
IV. Cell Cycle Control
Lecture Presentation by
Dr Burns
NVC Biol 120
© 2014 Pearson Education, Inc.
Overview: The Key Roles of Cell Division
Figure 12.1
 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
© 2011 Pearson Education, Inc.
Overview: The Key Roles of Cell Division
 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
Most cell division results in genetically
identical daughter cells
 Most cell division results in daughter cells with
identical genetic information, DNA
 The exception is meiosis, a special type of
division that can produce sperm and egg cells
(next weeks lab)
 Cell division is an integral part of the cell cycle,
the life of a cell from formation to its own division
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
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Cellular Organization of the Genetic Material
Figure 12.3
 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
20 m
© 2011 Pearson Education, Inc.
Chromosomes
 Eukaryotic chromosomes consist of
chromatin, a complex of DNA and protein
that condenses during cell division
 Every eukaryotic species has a characteristic
number of chromosomes in each cell nucleus
 Somatic cells (nonreproductive cells) have
two sets of chromosomes
 Gametes (reproductive cells: sperm and
eggs) have half as many chromosomes as
somatic cells
© 2011 Pearson Education, Inc.
Distribution of Chromosomes During
Eukaryotic Cell Division
 In preparation for cell division, DNA is replicated
and the chromosomes condense
 Each duplicated chromosome has two sister
chromatids (joined copies of the original
chromosome), which separate during cell division
 The centromere is the narrow “waist” of the
duplicated chromosome, where the two
chromatids are most closely attached
© 2011 Pearson Education, Inc.
Figure 12.4
Distribution of Chromosomes During
Eukaryotic Cell Division
 During cell division, the two sister chromatids
of each duplicated chromosome separate and
move into two nuclei
Sister
chromatids
Centromere
0.5 m
 Once separate, the chromatids are called
chromosomes
© 2011 Pearson Education, Inc.
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Figure 12.5-1
1
Figure 12.5-2
Chromosomal
DNA molecules
Chromosomes
Chromosomal
DNA molecules
Chromosomes
Centromere
1
Chromosome
arm
Centromere
Chromosome
arm
Chromosome duplication
(including DNA replication)
and condensation
2
Sister
chromatids
Figure 12.5-3
Chromosomal
DNA molecules
Chromosomes
1
The region where the chromatids are tightly
associated is called
Centromere
Chromosome
arm
1.
2.
3.
4.
Chromosome duplication
(including DNA replication)
and condensation
2
Centrosome
Chromatin
Centromere
Kinetochore
25%
25%
25%
2
3
25%
Sister
chromatids
Separation of sister
chromatids into
two chromosomes
3
1
Microtubule-organizing centers have two
4
Eukaryotic Cell Division
 Eukaryotic cell division consists of
1.
2.
3.
4.
Centrioles
Chromatins
Centromeres
Kinetochores
25%
25%
25%
25%
 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
1
2
3
4
© 2011 Pearson Education, Inc.
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The mitotic phase alternates with interphase
in the cell cycle
When does DNA replicate?
 Just prior to cell division
 In 1882, the German anatomist Walther
Flemming developed dyes to observe
chromosomes during mitosis and cytokinesis
 Cells need to divide for organisms to grow or to
replace old cells, or for one celled organisms to
reproduce
 Before a cell divides it needs to replicate its
DNA
© 2011 Pearson Education, Inc.
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)
Phases of the Cell Cycle - Interphase
 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
© 2011 Pearson Education, Inc.
The eukaryotic cell cycle is regulated by a
molecular control system
 The frequency of cell division varies with the type
of cell
 These differences result from regulation at the
molecular level
 Cancer cells manage to escape the usual
controls on the cell cycle
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
The Cell Cycle Control System
 The sequential events of the cell cycle are
directed by a distinct cell cycle control system,
which is similar to a clock
 The cell cycle control system is regulated by both
internal and external controls
 The clock has specific checkpoints where the
cell cycle stops until a go-ahead signal is
received
© 2011 Pearson Education, Inc.
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Figure 12.15
G1 checkpoint
The Cell Cycle Control System
 For many cells, the G1 checkpoint seems to be
the most important
Control
system
G1
M
S
 If a cell receives a go-ahead signal at the G1
checkpoint, it will usually complete the S, G2, and
M phases and divide
G2
 If the cell does not receive the go-ahead signal, it
will exit the cycle, switching into a nondividing
state called the G0 phase
M checkpoint
G2 checkpoint
© 2011 Pearson Education, Inc.
Figure 12.6
Figure 12.16
INTERPHASE
G0
G1 checkpoint
G1
S
(DNA synthesis)
G2
G1
(a) Cell receives a go-ahead
signal.
G1
(b) Cell does not receive a
go-ahead signal.
Mitotic Phase
 Mitosis is divided into four phases




Prophase
Metaphase
Anaphase
Telophase
 Cytokinesis overlaps the latter stages of
mitosis
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
BioFlix: Mitosis
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Figure 12.7
Figure 12.7a
G2 of Interphase
Chromatin
(duplicated)
Prophase
Early mitotic
spindle
Prometaphase
Fragments
of nuclear
Aster
envelope
Centromere
Nonkinetochore
microtubules
10 m
Centrosomes
(with centriole
pairs)
G2 of Interphase
Centrosomes
(with centriole pairs)
Nucleolus
Chromatin
(duplicated)
Nuclear
envelope
Plasma
membrane
Prophase
Early mitotic
spindle
Aster
Centromere
Prometaphase
Fragments
of nuclear
envelope
Chromosome, consisting
of two sister chromatids
Kinetochore
Metaphase
Nonkinetochore
microtubules
Kinetochore
microtubule
Anaphase
Metaphase
plate
Spindle
Centrosome at
one spindle pole
Telophase and Cytokinesis
Cleavage
furrow
Daughter
chromosomes
Nucleolus
forming
Nuclear
envelope
forming
Plasma
membrane
Nucleolus
Nuclear
envelope
Figure 12.7b
Chromosome, consisting
of two sister chromatids
Kinetochore
Kinetochore
microtubule
Figure 12.7c
Metaphase
Anaphase
Metaphase
plate
Telophase and Cytokinesis
Nucleolus
forming
10 m
Cleavage
furrow
G2 of Interphase
Spindle
Centrosome at
one spindle pole
Daughter
chromosomes
Prophase
Prometaphase
Nuclear
envelope
forming
Figure 12.7d
G2 of Interphase
G2 of Interphase
Chromatin
(duplicated)
10 m
Centrosomes
(with centriole
pairs)
Metaphase
Anaphase
Prometaphase
Prophase envelope
 Nuclear
present
 Centrosomes are duplicated
 Chromosomes are in the
duplicated state (DNA
replication occurred during S
phase of interphase)
Telophase and Cytokinesis
Plasma
membrane
Nucleolus
Nuclear
envelope
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Prophase
Late Prophase
 Chromosomes condense
 Nucleolus disappear
 Sister chromatids are joined
at the centromeres
 Mitotic spindle appears,
composed of centrosomes,
spindle microtubles and
asters
 Centrosomes move to
opposite poles of the cell
Prophase
Early mitotic
spindle
Aster
Centromere
Chromosome, consisting
of two sister chromatids
Metaphase
Prometaphase
Fragments
of nuclear
envelope
Nonkinetochore
microtubules
Kinetochore
Kinetochore
microtubule
Anaphase
 Centrosomes are at
Telophase and Cytokinesis
opposite ends
of cell
Metaphase
 Cohesion proteins are cleaved,
sister chromatids separate,
now each are a chromosome
 Kinetochore microtubules
shorten, moving the daughter
chromosomes to opposite
poles of the cell
 Cell elongates due to
nonkinetochore microtubules
lengthening
Anaphase
Metaphase
plate
 Chromosomes line up at
the metaphase plate
Spindle
Centrosome at
one spindle pole
Telophase
Telophase and Cytokinesis
Cleavage
furrow
Nuclear
envelope
forming
Nucleolus
forming
 Nuclear envelope
fragments
 Microtubles attach to the
kinetochore
Daughter
chromosomes
Cytokinesis
 Two identical daughter nuclei
form, nuclear envelopes form
 Nucleolus reappears
 Chromosomes uncondense
 Spindle microtubles
depolymerize
Telophase and Cytokinesis
Cleavage
furrow
Nucleolus
forming
 Cytoplasm divides
 In animal cells, cleavage
furrow pinches the cell in two
Nuclear
envelope
forming
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The Mitotic Spindle: A Closer Look
 The mitotic spindle is a structure made of
microtubules that controls chromosome
movement during mitosis
 In animal cells, assembly of spindle microtubules
begins in the centrosome, the microtubule
organizing center
 The centrosome replicates during interphase,
forming two centrosomes that migrate to opposite
ends of the cell during prophase
© 2011 Pearson Education, Inc.
The Mitotic Spindle: A Closer Look
The Mitotic Spindle: A Closer Look
 An aster (a radial array of short microtubules)
extends from each centrosome
 The spindle includes the centrosomes, the
spindle microtubules, and the asters
© 2011 Pearson Education, Inc.
Figure 12.8
Centrosome
Aster
 During prophase, some spindle microtubules
attach to the kinetochores of chromosomes and
begin to move the chromosomes
 Kinetochores are protein complexes associated
with centromeres
 At metaphase, the chromosomes are all lined up
at the metaphase plate, an imaginary structure
at the midway point between the spindle’s two
poles
Metaphase
plate
(imaginary)
Sister
chromatids
Microtubules
Chromosomes
Kinetochores
Centrosome
1 m
Overlapping
nonkinetochore
microtubules
Kinetochore
microtubules
0.5 m
© 2011 Pearson Education, Inc.
The Mitotic Spindle: A Closer Look
Figure 12.9
EXPERIMENT
Kinetochore
Spindle
pole
 In anaphase, sister chromatids separate and
move along the kinetochore microtubules
toward opposite ends of the cell
Mark
RESULTS
 The microtubules shorten by depolymerizing at
their kinetochore ends
CONCLUSION
Microtubule
Chromosome
movement
Motor protein
Kinetochore
Tubulin
subunits
Chromosome
© 2011 Pearson Education, Inc.
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The place where microtubules attach is called the
1.
2.
3.
4.
Centriole
Chromatin
Centromere
Kinetochore
25%
25%
25%
25%
50%
50%
1. Cytosol
2. Nucleus
1
2
3
1
4
During this stage the nuclear membrane breaks down
25%
1.
2.
3.
4.
Where does DNA replication take place?
25%
25%
During this stage chromosomes line up at the equator
25%
25%
Metaphase
Anaphase
Prophase
Telophase
1.
2.
3.
4.
1
2
3
2
25%
25%
2
3
25%
Metaphase
Anaphase
Prophase
Telophase
1
4
4
During this stage the chromosomes begin to uncondense
At the end of Mitosis the chromosomes are in the duplicated
state
25%
1.
2.
3.
4.
25%
25%
2
3
25%
Metaphase
Anaphase
Prophase
Telophase
1
4
1. Yes
2. No
50%
1
50%
2
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Animation: Cytokinesis
Animation: Animal Mitosis
Right-click slide / select ”Play”
© 2011 Pearson Education, Inc.
Right-click slide / select ”Play”
© 2011 Pearson Education, Inc.
Videos
 Youtube Mitosis in embryo
 Mitosis in newt lung cell
 Mitosis
Animation: Sea Urchin (Time Lapse)
Right-click slide / select ”Play”
© 2011 Pearson Education, Inc.
Cytokinesis: A Closer Look
Figure 12.10
(a) Cleavage of an animal cell (SEM)
(b) Cell plate formation in a plant cell (TEM)
 In animal cells, cytokinesis occurs by a process
known as cleavage, forming a cleavage furrow
 In plant cells, a cell plate made of cell wall
material forms during cytokinesis
 In bacteria, the new cell wall grows out from the
existing cell wall
100 m
Cleavage furrow
Contractile ring of
microfilaments
Vesicles
forming
cell plate
Wall of parent cell
Cell plate
1 m
New cell wall
Daughter cells
Daughter cells
© 2011 Pearson Education, Inc.
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Figure 12.12-1
Binary Fission in Bacteria
 Prokaryotes (bacteria and archaea) reproduce
by a type of cell division called binary fission
Origin of
replication
E. coli cell
1 Chromosome
replication
begins.
Cell wall
Plasma membrane
Bacterial chromosome
Two copies
of origin
 In binary fission, the chromosome replicates
(beginning at the origin of replication), and the
two daughter chromosomes actively move apart
 The plasma membrane pinches inward, dividing
the cell into two. New cell wall grows out from
old cell wall.
© 2011 Pearson Education, Inc.
Figure 12.12-2
Origin of
replication
E. coli cell
1 Chromosome
replication
begins.
2 Replication
continues.
Cell wall
Plasma membrane
1 Chromosome
replication
begins.
Origin
Origin of
replication
E. coli cell
Bacterial chromosome
Two copies
of origin
Origin
Figure 12.12-3
2 Replication
continues.
Cell wall
Plasma membrane
Bacterial chromosome
Two copies
of origin
Origin
Origin
3 Replication
finishes.
Figure 12.12-4
Origin of
replication
E. coli cell
1 Chromosome
replication
begins.
2 Replication
continues.
Cell wall
Plasma membrane
Bacterial chromosome
 Since prokaryotes evolved before eukaryotes,
mitosis probably evolved from binary fission
Two copies
of origin
Origin
The Evolution of Mitosis
Origin
 Certain protists exhibit types of cell division
that seem intermediate between binary fission
and mitosis
3 Replication
finishes.
4 Two daughter
cells result.
© 2011 Pearson Education, Inc.
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Figure 12.13
Bacterial
chromosome
(a) Bacteria
At the end of Mitosis the chromosomes are in the duplicated state
Chromosomes
Microtubules
(b) Dinoflagellates
1. Yes
2. No
Intact nuclear
envelope
50%
50%
Kinetochore
microtubule
(c) Diatoms and
some yeasts
Intact nuclear
envelope
Kinetochore
microtubule
(d) Most eukaryotes
Fragments of
nuclear envelope
1
2
Figure 12.UN05
At the end of mitosis in plants the cell wall forms by
1. Proteins constrict and
pinch off the new cell
2. Vesicles line up between
the cells and join together
3. The new cell wall grows
out from old cell wall
33%
1
33%
2
33%
3
Important concepts
 Know all the vocabulary presented in the
lecture
 Know the form (condensed vs uncondensed)
that DNA is in during cell division vs interphase
 Know the roles of microtubules in cell division
 Know the role of microtubule-organizing centers
 Know the two stages of cell cycle (interphase
and mitotic phase
Important concepts
 Know what happens during the stages of
interphase: G1 phase, S phase, G2 phase.
 Know the role of microfilaments in cell division
of animal cells, the structure of microfilaments
 Understand how cytokinesis takes place in
animal, bacteria and plant cells
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Important Concepts for Lab Exam
 For Mitosis: Know each stage, the order of the
stages, and what happens in each stage.
 Know what the end result is of mitosis
 Know what state the cell and the
chromosomes are in at the beginning and end
of mitosis. For example: Are the cells haploid
or diploid? Are the chromosomes duplicated,
or not duplicated? How many chromosomes
are there in the cell? Are they in pairs?
 Be able to identify the stages using models
and slides
13