1. INTERPHASE S (DNA synthesis) G1 G2 MITOTIC
INTERPHASE S
(DNA synthesis) G1 G2
Cytokinesis
Mitosis
Figure 8.5 The eukaryotic cell cycle.
MITOTIC
PHASE (M)

2. 8.6 Cell division is a continuum of dynamic changes
Mitosis progresses through a series of stages
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis often overlaps telophase
Teaching Tips
1. Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym.
2. The authors note that animals, but not plants, have a pair of centrioles in their centrosomes. They add that the role of centrioles in cell division is a mystery. Students might not appreciate all that remains to be explained in biology. Sharing the existence of such mysteries with them promotes critical thinking skills and helps them imagine a place for themselves in future research.
Copyright © 2009 Pearson Education, Inc.

3. 8.6 Cell division is a continuum of dynamic changes
A mitotic spindle is required to divide the chromosomes
Composed of microtubules
produced by centrosomes, structures in the cytoplasm that
Organize microtubule arrangement
Contain a pair of centrioles in animal cells
Centrioles give rise to basal bodies that are the foundations for cilia and flagella. They are found in animal cells but also in plants such as mosses and ferns that have swimming sperm. They are not found in flowering plants, showing that centrioles are not essential for spindle formation. There is other evidence, however, that suggests centrioles may influence progression through alternative stages in the cell cycle, including entry into the S phase and completion of cytokinesis. (Reviewed in A. W. Murray, 2001, “Centrioles at the Checkpoint,” Science, 291:1499–1501.)
For the BioFlix Animation Mitosis, go to Animation and Video Files.
Teaching Tips
1. Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym.
2. The authors note that animals, but not plants, have a pair of centrioles in their centrosomes. They add that the role of centrioles in cell division is a mystery. Students might not appreciate all that remains to be explained in biology. Sharing the existence of such mysteries with them promotes critical thinking skills and helps them imagine a place for themselves in future research.
Video: Animal Mitosis
Video: Sea Urchin (time lapse)
Copyright © 2009 Pearson Education, Inc.

4. INTERPHASE PROPHASE PROMETAPHASE
INTERPHASE
PROPHASE
PROMETAPHASE
Centrosomes
(with centriole pairs)
Chromatin
Early mitotic
spindle
Centrosome
Fragments
of nuclear
envelope
Kinetochore
Figure 8.6 The stages of cell division.
Centromere
Nuclear
envelope
Plasma
membrane
Spindle
microtubules
Chromosome, consisting
of two sister chromatids
Nucleolus

5. INTERPHASE PROPHASE PROMETAPHASE
INTERPHASE
PROPHASE
PROMETAPHASE
Centrosomes
(with centriole pairs)
Chromatin
Early mitotic
spindle
Centrosome
Fragments
of nuclear
envelope
Kinetochore
Figure 8.6 The stages of cell division.
Centromere
Nuclear
envelope
Plasma
membrane
Spindle
microtubules
Chromosome, consisting
of two sister chromatids
Nucleolus

6. Figure 8.6 The stages of cell division.
INTERPHASE

7. Figure 8.6 The stages of cell division.
PROPHASE

8. Figure 8.6 The stages of cell division.
PROMETAPHASE

9. 8.6 Cell division is a continuum of dynamic changes
Interphase
In the cytoplasm
Cytoplasmic contents double
Two centrosomes form
In the nucleus
Chromosomes duplicate during the S phase
Nucleoli are visible
Teaching Tips
1. Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym.
2. The authors note that animals, but not plants, have a pair of centrioles in their centrosomes. They add that the role of centrioles in cell division is a mystery. Students might not appreciate all that remains to be explained in biology. Sharing the existence of such mysteries with them promotes critical thinking skills and helps them imagine a place for themselves in future research.
Copyright © 2009 Pearson Education, Inc.

10. 8.6 Cell division is a continuum of dynamic changes
Applying Your Knowledge Human cells have 46 chromosomes. By the end of interphase
How many chromosomes are present in one cell?
How many chromatids are present in one cell?
Applying Your Knowledge Human cells have 46 chromosomes. By the end of interphase,
How many chromosomes are present in one cell? 46
How many chromatids are present in one cell? 92 (Each chromosome has been duplicated and consists of a pair of chromatids joined at the centromere.)
Teaching Tips
1. Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym.
2. The authors note that animals, but not plants, have a pair of centrioles in their centrosomes. They add that the role of centrioles in cell division is a mystery. Students might not appreciate all that remains to be explained in biology. Sharing the existence of such mysteries with them promotes critical thinking skills and helps them imagine a place for themselves in future research.
Copyright © 2009 Pearson Education, Inc.

11. 8.6 Cell division is a continuum of dynamic changes
Prophase
Cytoplasm:
Microtubules form spindle
Nucleus:
Chromosomes compact
Nucleoli disappear
Teaching Tips
1. Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym.
2. The authors note that animals, but not plants, have a pair of centrioles in their centrosomes. They add that the role of centrioles in cell division is a mystery. Students might not appreciate all that remains to be explained in biology. Sharing the existence of such mysteries with them promotes critical thinking skills and helps them imagine a place for themselves in future research.
Copyright © 2009 Pearson Education, Inc.

12. 8.6 Cell division is a continuum of dynamic changes
Prometaphase
Spindle microtubules reach chromosomes, where they
Attach at kinetochores on the centromeres of sister chromatids
Move chromosomes to the center of the cell through associated protein “motors”
Other microtubules meet those from the opposite poles
The nuclear envelope disappears
Teaching Tips
1. Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym.
2. The authors note that animals, but not plants, have a pair of centrioles in their centrosomes. They add that the role of centrioles in cell division is a mystery. Students might not appreciate all that remains to be explained in biology. Sharing the existence of such mysteries with them promotes critical thinking skills and helps them imagine a place for themselves in future research.
Copyright © 2009 Pearson Education, Inc.

13. TELOPHASE AND CYTOKINESIS
METAPHASE
ANAPHASE
TELOPHASE AND CYTOKINESIS
Nucleolus
forming
Metaphase
plate
Cleavage
furrow
Figure 8.6 The stages of cell division.
Nuclear
envelope
forming
Daughter
chromosomes
Spindle

14. TELOPHASE AND CYTOKINESIS
METAPHASE
ANAPHASE
TELOPHASE AND CYTOKINESIS
Nucleolus
forming
Metaphase
plate
Cleavage
furrow
Figure 8.6 The stages of cell division.
Nuclear
envelope
forming
Daughter
chromosomes
Spindle

15. Figure 8.6 The stages of cell division.
METAPHASE

16. Figure 8.6 The stages of cell division.
ANAPHASE

17. TELOPHASE AND CYTOKINESIS
Figure 8.6 The stages of cell division.
TELOPHASE AND CYTOKINESIS

18. 8.6 Cell division is a continuum of dynamic changes
Metaphase
Spindle is fully formed
Chromosomes align at the cell equator
Kinetochores of sister chromatids are facing the opposite poles of the spindle
Applying Your Knowledge By the end of metaphase
How many chromosomes are present in one human cell?
How many chromatids are present in one human cell?
Applying Your Knowledge
By the end of metaphase,
How many chromosomes are present in one human cell? 46
How many chromatids are present in one human cell? 92
Teaching Tips
1. Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym.
2. The authors note that animals, but not plants, have a pair of centrioles in their centrosomes. They add that the role of centrioles in cell division is a mystery. Students might not appreciate all that remains to be explained in biology. Sharing the existence of such mysteries with them promotes critical thinking skills and helps them imagine a place for themselves in future research.
Copyright © 2009 Pearson Education, Inc.

19. 8.6 Cell division is a continuum of dynamic changes
Anaphase
Sister chromatids separate at the centromeres
Daughter chromosomes are moved to opposite poles of the cell
The cell elongates due to lengthening of nonkinetochore microtubules
Applying Your Knowledge By the end of anaphase
How many chromosomes are present in one human cell?
How many chromatids are present in one human cell?
Applying Your Knowledge
By the end of anaphase,
How many chromosomes are present in one cell? 92 (Once the sister chromatids separate, they are considered to be individual chromosomes.)
How many chromatids are present in one cell? 0
Teaching Tips
1. Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym.
2. The authors note that animals, but not plants, have a pair of centrioles in their centrosomes. They add that the role of centrioles in cell division is a mystery. Students might not appreciate all that remains to be explained in biology. Sharing the existence of such mysteries with them promotes critical thinking skills and helps them imagine a place for themselves in future research.
Copyright © 2009 Pearson Education, Inc.

20. 8.6 Cell division is a continuum of dynamic changes
Telophase
The cell continues to elongate
The nuclear envelope forms around chromosomes at each pole, establishing daughter nuclei
Chromatin uncoils
Nucleoli reappear
The spindle disappears
Applying Your Knowledge By the end of telophase
How many chromosomes are present in one nucleus within the human cell?
Are the nuclei identical or different?
Applying Your Knowledge
By the end of telophase,
How many chromosomes are present in one nucleus within the human cell? 46
Are the nuclei identical or different? Identical
Teaching Tips
1. Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym.
2. The authors note that animals, but not plants, have a pair of centrioles in their centrosomes. They add that the role of centrioles in cell division is a mystery. Students might not appreciate all that remains to be explained in biology. Sharing the existence of such mysteries with them promotes critical thinking skills and helps them imagine a place for themselves in future research.
Copyright © 2009 Pearson Education, Inc.

21. 8.6 Cell division is a continuum of dynamic changes
Cytokinesis
Cytoplasm is divided into separate cells
Applying Your Knowledge By the end of cytokinesis
How many chromosomes are present in one human cell?
How many chromatids are present in one human cell?
Applying Your Knowledge
By the end of cytokinesis,
How many chromosomes are present in one human cell? 46
How many chromatids are present in one human cell? 0 (Chromatids will not be present until after the next S phase.)
Teaching Tips
1. Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym.
2. The authors note that animals, but not plants, have a pair of centrioles in their centrosomes. They add that the role of centrioles in cell division is a mystery. Students might not appreciate all that remains to be explained in biology. Sharing the existence of such mysteries with them promotes critical thinking skills and helps them imagine a place for themselves in future research.
Copyright © 2009 Pearson Education, Inc.

22. 8.7 Cytokinesis differs for plant and animal cells
Cytokinesis
Cleavage in animal cells
A cleavage furrow forms from a contracting ring of microfilaments, interacting with myosin
The cleavage furrow deepens to separate the contents into two cells
Cytokinesis in plant cells
A cell plate forms in the middle from vesicles containing cell wall material
The cell plate grows outward to reach the edges, dividing the contents into two cells
Each cell has a plasma membrane and cell wall
This material allows a review of cellular components. Students can be reminded that microtubules are composed of actin molecules and that actin and myosin work in concert for muscle cell contraction. They can also be reminded that vesicles have a lipid boundary that will contribute to the plasma membrane of the new plant cells.
For the BLAST Animation Cytokinesis in Plants, go to Animation and Video Files.
Teaching Tips
1. Many students think of mitosis and cytokinesis as one process. In some situations, mitosis occurs without subsequent cytokinesis. Challenge your students to predict the outcome of mitosis without cytokinesis (multinuclear cells called a syncytium). This occurs in human development during the formation of the placenta.
2. The authors make an analogy between a drawstring and the mechanism of cytokinesis in animal cells. Students seem to appreciate this association. Have your students think of a person tightening the drawstring of sweatpants so tight that they pinch themselves in two, or perhaps nearly so! The analogy is especially good because, like the drawstring just beneath the surface of the sweat pants, the microfilaments are just beneath the surface of the cell’s plasma membrane.
Animation: Cytokinesis
Copyright © 2009 Pearson Education, Inc.

23. Cleavage furrow Cleavage furrow Contracting ring of microfilaments
Cleavage
furrow
Cleavage furrow
Contracting ring of
microfilaments
Figure 8.7A Cleavage of an animal cell.
Daughter cells

24. Figure 8.7A Cleavage of an animal cell.
furrow

25. Cleavage furrow Contracting ring of microfilaments Daughter cells
Figure 8.7A Cleavage of an animal cell.
Daughter cells

26. Wall of parent cell Cell plate forming Daughter nucleus Cell wall
Cell wall
New cell wall
Figure 8.7B Cell plate formation in a plant cell.
Vesicles containing
cell wall material
Cell plate
Daughter cells

27. Wall of parent cell Cell plate forming Daughter nucleus
Wall of
parent cell
Cell plate
forming
Daughter
nucleus
Figure 8.7B Cell plate formation in a plant cell.

28. Cell wall New cell wall Vesicles containing cell wall material
Cell wall
New cell wall
Figure 8.7B Cell plate formation in a plant cell.
Vesicles containing
cell wall material
Cell plate
Daughter cells