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Sinauer Associates, Inc. W. H. Freeman and Company
Lecture Notebook to accompany
Copyright © 2012 Sinauer Associates, Inc. Cover photograph © Fred Bavendam/Minden Pictures.
This document may not be modified or distributed (either electronically or on paper) without the permission of the publisher, with the following exception: Individual users may enter their own notes into this document and may print it for their own personal use.
© 2012 Sinauer Associates, Inc.
The Cell Cycle and Cell Division 7
2
To add your own notes to any page, use Adobe Reader’s Typewriter feature, accessible via the Typewriter bar at the top of the window. (Requires Adobe Reader 8 or newer. Adobe Reader can be downloaded free of charge from the Adobe website: http://get.adobe.com/reader.)
POL Sadava Sinauer AssociatesMorales Studio Figure 07.01 Date 07-20-10
(A) Reproduction
(C) Regeneration
(B) Growth
These yeast cells divide by budding.
Cell division contributes to the regeneration of a lizard’s tail.
Cell division contributes to the growth of this root.
2 µm
FIGURE 7.1 The Importance of Cell Division (Page 125)
© 2012 Sinauer Associates, Inc.
Chapter 7 | The Cell Cycle and Cell Division 3
FIGURE 7.2 Asexual Reproduction on a Large Scale (Page 125)
POL Sadava Sinauer AssociatesMorales Studio Figure 07.03 Date 07-21-10
In the haplontic life cycle, the mature organism is haploid and the zygote is the only diploid stage.
In alternation of generations, the organism passes through haploid and diploid stages that are both multicellular.
In the diplontic life cycle, the organism is diploid and the gametes are the only haploid stage.
Sporophyte(2n)
Zygote (2n)
GametesMale (n) Female (n)
Spore (n)
Gametophyte(n)
Mature organism (n)
GametesMale (n) Female (n)
Matureorganism (2n)
Zygote (2n)
GametesMale (n) Female (n)
Bread mold (Rhizopus stolonifer) (haploid organism)
Fern (Asplenium trichomanes) (diploid sporophyte)
African fish eagle (Haliaeetus vocifer) (diploid organism)
DIPLOID (2n)
DIPLOID (2n)
HAPLOID (n) HAPLOID (n)
DIPLOID (2n)
HAPLOID (n)
Spores (n)
Zygote (2n)
Meiosis
Meiosis
Meiosis
Fertilization
Fertilization
Fertilization
50 µm
FIGURE 7.3 All Sexual Life Cycles Involve Fertilization and Meiosis (Page 126)
© 2012 Sinauer Associates, Inc.
Chapter 7 | The Cell Cycle and Cell Division 4
POL Sadava Sinauer AssociatesMorales Studio Figure 07.04 Date 07-21-10
Plasma membrane
Chromosome
ori
DNA replication begins at the origin of replication at the center of the cell.
1
The chromosomal DNA replicates as the cell grows.
2
Cytokinesis is complete; two new cells are formed.
4
The daughter DNAs separate, led by the region including ori. The cell begins to divide.
3
FIGURE 7.4 Prokaryotic Cell Division (Page 128)
POL HillisSinauer AssociatesMorales Studio Figure 07.05 Date 07-08-10
In the M phase cell, the DNA and proteins in each chromosome form highly compact structures.
During interphase, DNA is replicated. Only a tiny portion of one chromosome is shown.
In an interphase nucleus, chromosomesare threadlike structures dispersed throughout the nucleus.
Centromere
Sisterchromatids
G1
M
G2
S
Interphase
5 µm
0.5 µm
FIGURE 7.5 The Phases of the Eukaryotic Cell Cycle (Page 129)
© 2012 Sinauer Associates, Inc.
Chapter 7 | The Cell Cycle and Cell Division 5
POL Sadava Sinauer AssociatesMorales Studio Figure Intext #1 Date 07-21-10
Polar microtubules extend from each pole of the spindle.
Kinetochore microtubules attach to the kinetochores and to the spindle poles.
Polarmicrotubule
Centrosome
Centriole
Kinetochore
Kinetochoremicrotubule
IN-TEXT ART (Page 129)
POL Sadava Sinauer AssociatesMorales Studio Figure 07.06 LEFT Date 07-21-10
During the S phase of interphase, the nucleus replicates its DNA and centrosomes.
1 The chromatin coils and supercoils, becoming more and more compact and condensing into visible chromosomes. The chromosomes consist of identical, paired sister chromatids. Centrosomes move to opposite poles.
2 The nuclear envelope breaks down. Kinetochore microtubules appear and connect the kinetochores to the poles.
3
Interphase Prophase Prometaphase
Nuclear envelope Kinetochore
microtubules
Kinetochore
Nuclear envelope
Nucleus Nucleolus
Centrosomes
Developingspindle
Chromatids ofchromosome
FIGURE 7.6 The Phases of Mitosis (Pages 130 and 131)
© 2012 Sinauer Associates, Inc.
Chapter 7 | The Cell Cycle and Cell Division 6
POL Sadava Sinauer AssociatesMorales Studio Figure 07.06RIGHT Date 07-21-10
The centromere/kinetochore complexes become aligned in a plane, which is often at the cell’s equator.
4 The paired sister chromatids separate, and the new daughter chromosomes begin to move toward the poles.
5 The daughter chromosomes reach the poles. As telophase concludes, the nuclear envelopes and nucleoli re-form, the chromatin decondenses, and, after cytokinesis, the daughter cells enter interphase once again.
6
Metaphase Anaphase Telophase
Equatorial(metaphase)plate
Daughterchromosomes
FIGURE 7.6 The Phases of Mitosis (continued)
© 2012 Sinauer Associates, Inc.
Chapter 7 | The Cell Cycle and Cell Division 7
POL Sadava Sinauer AssociatesMorales Studio Figure 07.07 Date 07-21-10
The contractile ring has completely separated the cytoplasms of these two daughter cells, although their surfaces remain in contact.
This row of vesicles will fuse to form a cell plate between the cell above and the cell below.
50 µm10 µm
(A) (B)
Contractilering
Cell plate
FIGURE 7.7 Cytokinesis Differs in Animal and Plant Cells (Page 132)
POL HillisSinauer AssociatesMorales Studio Figure 07.08 Date 07-08-10
Nuclear division occurs during mitosis.
DNA is replicated during S phase.
Cells that do not divide are usually arrestedin the G1 phase.
Transition from G1 to S is regulated at the restriction point.
Cell division—cytokinesis—occurs at theend of the M phase.
Mitosis(M)
G1
Restriction point (R)
G2
DNA synthesis(S)
Interphase
FIGURE 7.8 The Eukaryotic Cell Cycle (Page 133)
© 2012 Sinauer Associates, Inc.
Chapter 7 | The Cell Cycle and Cell Division 8
POL HillisSinauer AssociatesMorales Studio Figure 07.09 Date 06-15-10
HYPOTHESIS
CONCLUSION
INVESTIGATION
Go to yourBioPortal.com for original citations, discussions,and relevant links for all INVESTIGATION figures.
The S phase cell produces a substance that diffuses to theG1 nucleus and activates DNA replication.
A cell in S phase contains an activatorof DNA replication.
METHOD
FIGURE 7.9 Regulation of the Cell Cycle Nuclei in G1 do not undergo DNA replication, but nuclei in S phase do. To determine if there is some signal in the S cells that stimulates G1 cells to replicate their DNA, cells in the G1 and S phases were fused together, creating cells with both G1 and S properties.
RESULTS
ANALYZE THE DATA
The experiment used mammalian cells undergoing the cell cyclesynchronously. Radioactive labeling and microscopy were used to
determine which nuclei were synthesizing DNA.Here are counts of the cell nuclei that were labeled:
A. What were the percentages of cells in S phase in each of the three experiments? B. What does this mean in terms of control of the cell cycle?
Cells are fused in polyethylene glycol.
Both nuclei in the fused cell enter S phase.
In S phase
The fused cell has two nuclei
In G1 phase
DNAreplication
DNAreplication
Cells with labeledType of cells nuclei/total cells
Unfused G1: 6/300Unfused S: 435/500Fused G1 and S cells: 17*/19
*Both nuclei labeled
(Page 133)
© 2012 Sinauer Associates, Inc.
Chapter 7 | The Cell Cycle and Cell Division 9
POL HillisSinauer AssociatesMorales Studio Figure 07.10 Date 07-08-10
Cdk is present, but without cyclin it is not active.
Cyclin synthesisbegins during G1.
Cyclin binds to Cdk,which becomes active.
Cyclin breaks down.Cdk is
inactive.
Mitosis(M)
G1G2
DNA synthesis(S)
CyclinCdk
Cdk
CdkCdk
Cdk
Cdk
Cdk
Restriction point (R)
FIGURE 7.10 Cyclins Are Transient in the Cell Cycle (Page 134)
© 2012 Sinauer Associates, Inc.
Chapter 7 | The Cell Cycle and Cell Division 10
POL Sadava Sinauer AssociatesMorales Studio Figure 07.12 ALTERNATE LAYOUT Date 07-21-10
No pairing of homologous chromosomes.
1
Individual chromosomes align at the equatorial plate.
2
Centromeres separate. Sister chromatids separate during anaphase, becoming daughter chromosomes.
3
Pairing and crossing over of homologs.
1
Homologous pairs align at the equatorial plate.
2
Centromeres do not separate; sisterchromatids remaintogether duringanaphase; homologs separate; DNA does not replicate before prophase II.
3
Mitosis is a mechanism for constancy:The parent nucleus produces two genetically identical daughter nuclei.
At the end of telophase I, the two homologs are segregated from one another.
Meiosis II produces four haploid daughter cells that are genetically distinct. Meiosis is thus a mechanism for generating diversity.
Pairs ofhomologs
Prophase
Metaphase
Anaphase
MITOSIS MEIOSIS
Parent cell (2n) Parent cell (2n)
Prophase I
Metaphase I
Anaphase I
Two daughter cells (each 2n)
2n 2n2n 2n
n n n nn n n nFour daughter cells (each n)
Telophase I
FIGURE 7.11 Mitosis and Meiosis: A Comparison (Page 135)
© 2012 Sinauer Associates, Inc.
Chapter 7 | The Cell Cycle and Cell Division 11
© 2012 Sinauer Associates, Inc.
Chapter 7 | The Cell Cycle and Cell Division 12
POL Sadava Sinauer AssociatesMorales Studio Figure 07.11LEFT Date 07-21-10
The chromatin begins to condense following interphase.
1
The chromosomes condense again,following a brief interphase (interkinesis)in which DNA does not replicate.
7 8 9
Synapsis aligns homologs, and chromosomes condense further.
2 The chromosomes continue to coil and shorten. The chiasmata reflect crossing over, the exchange of genetic material between nonsister chromatids in a homologous pair. In prometa-phase the nuclear envelope breaks down.
3
The centromeres of the paired chromatids line up across the equatorial plates of each cell.
The chromatids finally separate, becoming chromosomes in their own right, and arepulled to opposite poles. Because of crossingover and independent assortment, each new cell will have a different genetic makeup.
Early prophase I Mid-prophase I Late prophase I–Prometaphase
Prophase II Metaphase II Anaphase II
Pairs ofhomologs
TetradChiasma
Centrosomes
Equatorial plate
MEIOSIS I
MEIOSIS II
FIGURE 7.12 Meiosis: Generating Haploid Cells (Pages 136 and 137)
© 2012 Sinauer Associates, Inc.
Chapter 7 | The Cell Cycle and Cell Division 13
POL Sadava Sinauer AssociatesMorales Studio Figure 07.11RIGHT Date 07-21-10
The homologous pairs line up on the equatorial (metaphase) plate.
4
The chromosomes gather into nuclei, and the cells divide.
10 11
The homologous chromosomes (each with two chromatids) move to opposite poles of the cell.
5 The chromosomes gather into nuclei, and the original cell divides.
6
Each of the four cells has a nucleus with a haploid number of chromosomes.
Metaphase I Anaphase I Telophase I
Telophase II Products
Equatorial plate
FIGURE 7.12 Meiosis: Generating Haploid Cells (continued)
© 2012 Sinauer Associates, Inc.
Chapter 7 | The Cell Cycle and Cell Division 14
© 2012 Sinauer Associates, Inc.
Chapter 7 | The Cell Cycle and Cell Division 15
POL HillisSinauer AssociatesMorales Studio Figure Intext 07.03 Date 08-03-10
Chiasmata
Centromeres
Homologouschromosomes
IN-TEXT ART (Page 138)
POL HillisSinauer AssociatesMorales Studio Figure Intext 07.13 Date 08-03-10
During prophase I, homologous chromosomes, each with a pair of sister chromatids, line up to form a tetrad.
Adjacent chromatids of different homologs break and rejoin. Because there is still sister chromatid cohesion, a chiasma forms.
The chiasma is resolved. Recombinant chromatids contain genetic material from different homologs.
Homologouschromosomes
Chiasma
Recombinant chromatids
Sisterchromatids
FIGURE 7.13 Crossing Over Forms Genetically Diverse Chromosomes (Page 139)
POL HillisSinauer AssociatesMorales Studio Figure In text 07.04 Date 07-08-10
abl
bcr
#9
#22
IN-TEXT ART (Page 140)
© 2012 Sinauer Associates, Inc.
Chapter 7 | The Cell Cycle and Cell Division 16
POL Sadava Sinauer AssociatesMorales Studio Figure 07.23 Date 07-21-10
Inactive caspase changes its structure to become active.
A cell in apoptosis displays extensive membrane blebbing.
A normal whiteblood cell.
2
External signals can bind to a receptor protein.
Caspase hydrolyzes nuclear proteins, nucleosomes, etc.,resulting in apoptosis.
3
1a
Internal signals can bind to mitochondria, releasing other signals.
1b(B)(A)
FIGURE 7.14 Apoptosis: Programmed Cell Death (Page 141)
POL HillisSinauer AssociatesMorales Studio Figure 07.15 Date 07-08-10
There are few copies of the growth factor receptor HER2 on normal breast cells.
In breast cancer, changes in DNA may result in many receptors, making the cell sensitive to growth factor stimulation.
In normal cervical cells, RBprotein acts to inhibit cellcycle initiation.
In cervical cancer, a virus makes a protein that inactivates RB, so thecell cycle proceeds uncontrolled.
(A)
(B)
HER2
RB
cell cycle proceeds uncontrolled.
XXX
FIGURE 7.15 Molecular Changes Regulate the Cell Cycle in Cancer Cells (Page 142)