1. The Cell Cycle
AP BIOLOGY
Ms. Day

2. Practice…How many chromosomes are present in…?
Organism Clue
Body Cell #
Sex cell #
Diploid #
Haploid #
a leaf cell of corn has 20 chromosomes
an egg cell of a gorilla has 24 chromosomes
a human liver cell has 46 chromosomes
a gamete of a housefly has 6 chromosomes

3. Practice…How many chromosomes are present in…?
Organism Clue
Body Cell #
Sex cell #
Diploid #
Haploid #
a leaf cell of corn has 20 chromosomes 20 10
an egg cell of a gorilla has 24 chromosomes 48 24
a human liver cell has 46 chromosomes 46 23
a gamete of a housefly has 6 chromosomes 12 6

4. The Cell Cycle
The mitotic phase alternates with interphase in the cell cycle
Interphasemitosisinterphasemitosis

5. Phases of the Cell Cycle
The cell cycle consists of
The mitotic (M) phase
Interphase (90% of the cell’s life)
INTERPHASE G1
S (DNA synthesis) G2
Cytokinesis Mitosis
MITOTIC (M) PHASE
Figure 12.5

6. Interphase can be divided into subphases
G1 phase (GAP 1 phase)
cell grows in size
varies most in length from cell to cell
S phase (synthesis phase)
DNA is copied (DNA replication)
Single  Double
Other organelles are copied
(ex: centrosomes in animal cells)
G2 phase (GAP 2 phase)
More growth and preparation (make proteins) for mitosis

7. Another G phase of Interphase
Called G0 phase called the resting phase
The cell exits the “cycle” and (usually) does NOT reproduce again
Ex: muscle cells, nerve cells, red blood cells

8. Interphase “Intermission” or “Inbetween”
not part of mitosis
Includes stages G1, S, and G2 of the cell cycle
DNA is in chromatin form
Nucleus & nucleolus present
Longest phase of cell cycle

10. The Mitotic (M) phase Is made up of 2 parts
1. Mitosis division of the nucleus (called Karyokinesis)
2. Cytokinesis  division of the cytoplasm

11. Mitosis Continuous pathway (Early, Mid, & Late)
Consists of 4 phases and cytokinesis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

13. Mitotic Spindle Fibers
Two types of spindle fibers
Kinetochore fibers
Polar fibers

14. Prophase (X’s) “Pack Together”
Chromatin  Chromosomes
DNA “packs” together
Mitotic spindle fibers form from centrosomes
Centrioles are in centromsomes in animals
appear as asters in animals
Microtubule Organizing Centers (MTOC’s) (in plants)
Centrosomes & Spindle fibers move towards “poles”
Late: Nucleus and nucleolus disappear
kinetochore fibers attach to each kinetochore on each chromosome  they begin to migrate toward the cell center

15. Kinetochore microtubule
G2 OF INTERPHASE
PROPHASE
PROMETAPHASE
Centrosomes (with centriole pairs)
Chromatin (duplicated)
Early mitotic spindle
Aster
Centromere
Fragments of nuclear envelope
Kinetochore
Nucleolus
Nuclear envelope
Plasma membrane
Chromosome, consisting of two sister chromatids
Kinetochore microtubule
Figure 12.6
Nonkinetochore microtubules

16. Metaphase (X’s) “Meet in the Middle”
Chromosomes line up in the middle of cell
Called equatorial or metaphase plate
Spinder fibers pull and tug chromosomes to line up
SAME IN PLANTS AND ANIMALS

17. Anaphase (V’s) “Adios and Away”
SISTER CHROMATIDS separate and begin moving to opposite ends (poles) of the cell
Polar fibers lengthen and elongate the cell
Late anaphase  each pole contains a complete set of single chromosomes
NOTE: This is the only time there is DOUBLE the amount of DNA in ONE cell

18. http://faculty.plattsburgh.edu/donald.slish/Motors.html Chromosome
Fig. 12-8b
Chromosome
movement
Kinetochore
Tubulin
Subunits
Motor
protein
Microtubule
Figure 12.8 At which end do kinetochore microtubules shorten during anaphase?
Chromosome

19. SAME IN PLANTS AND ANIMALS
NOT CHROMATIDS NOW!!!

20. TELOPHASE AND CYTOKINESIS
Centrosome at one spindle pole
Daughter chromosomes
METAPHASE
ANAPHASE
TELOPHASE AND CYTOKINESIS
Spindle
Metaphase plate
Nucleolus forming
Cleavage furrow
Nuclear envelope forming
Figure 12.6

21. Telophase (V’s) “Two New Cells”
Spindle fibers dissappear
2 daughter nuclei
2 nucleoli begin to form at EACH pole
Chromosomes  chromatin
OPPOSITE OF PROPHASE

22. Cytokinesis “Division of the Cytoplasm”
Occurs in Late telophase
In animal cells
a cleavage furrow forms, which pinches the cell in two.
In plant cells
vesicles from the Golgi apparatus produce a cell plate at the middle of the cell
At the end of cytokinesis, there are two distinct IDENTICAL daughter cells.

23. Cytokinesis: A Closer Look
Cleavage furrow
Contractile ring of microfilaments
Daughter cells
100 µm
(a) Cleavage of an animal cell (SEM)
Figure 12.9 A
In animal cells
Cytokinesis occurs by a process known as cleavage, forming a cleavage furrow

25. (b) Cell plate formation in a plant cell (SEM)
In plant cells, during cytokinesis
A cell plate forms
Daughter cells
1 µm
Vesicles forming cell plate
Wall of patent cell
Cell plate
New cell wall
(b) Cell plate formation in a plant cell (SEM)
Figure 12.9 B

26. Kinetochore microtubule
G2 OF INTERPHASE
PROPHASE
PROMETAPHASE
Centrosomes (with centriole pairs)
Chromatin (duplicated)
Early mitotic spindle
Aster
Centromere
Fragments of nuclear envelope
Kinetochore
Nucleolus
Nuclear envelope
Plasma membrane
Chromosome, consisting of two sister chromatids
Kinetochore microtubule
Figure 12.6
Nonkinetochore microtubules

27. TELOPHASE AND CYTOKINESIS
Centrosome at one spindle pole
Daughter chromosomes
METAPHASE
ANAPHASE
TELOPHASE AND CYTOKINESIS
Spindle
Metaphase plate
Nucleolus forming
Cleavage furrow
Nuclear envelope forming
Figure 12.6

29. Mitosis in a plant cell Nucleus Chromatine condensing Chromosome1
Prophase. The chromatin is condensing. The nucleolus is beginning to disappear. Although not yet visible in the micrograph, the mitotic spindle is staring to from.
Prometaphase. We now see discrete chromosomes; each consists of two identical sister chromatids. Later in prometaphase, the nuclear envelop will fragment.
Metaphase. The spindle is complete, and the chromosomes, attached to microtubules at their kinetochores, are all at the metaphase plate.
Anaphase. The chromatids of each chromosome have separated, and the daughter chromosomes are moving to the ends of cell as their kinetochore microtubles shorten.
Telophase. Daughter nuclei are forming. Meanwhile, cytokinesis has started: The cell plate, which will divided the cytoplasm in two, is growing toward the perimeter of the parent cell. 2 3 4 5
Nucleus
Nucleolus
Chromosome
Chromatine condensing
Figure 12.10

30. Cell Cycle and Mitosis Animations

31. Remember… Cell Cycle = “IPMATc” Mitosis = “PMATc”
Pass My Accelerated Tough Class
Let’s do the Mitosis Hand Cheer!