1. Dispatch
1) Explain the structure and function of a chromosome 2) Copy and fill in
Organism
Diploid # (in somatic cells)
Haploid # (in gametes)
Cat
Rose
Goat
Rice
Dog
Chimpanzees

2. Chapter 12
The Cell Cycle

3. http://highered. mcgraw-hill

4. Mitosis in Action Spindle=_________ Nucleus=_________
Cell Membrane=______
Chromosome=______

5. 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

6. Concept 12.1: Cell division results in genetically identical daughter cells
Cells duplicate their genetic material before they divide, ensuring that each daughter cell receives an exact copy of the genetic material, DNA
A dividing cell duplicates its DNA, allocates the two copies to opposite ends of the cell, and only then splits into daughter cells

7. Cellular Organization of the Genetic Material
A cell’s endowment of DNA (its genetic information) is called its genome
DNA molecules in a cell are packaged into chromosomes

8. Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus
Somatic (nonreproductive) cells have two sets of chromosomes
Gametes (reproductive cells: sperm and eggs) have half as many chromosomes as somatic cells
Eukaryotic chromosomes consist of chromatin, a complex of DNA and protein that condenses during cell division

9. Distribution of Chromosomes During Cell Division
In preparation for cell division, DNA is replicated and the chromosomes condense
Each duplicated chromosome has two sister chromatids, which separate during cell division
The centromere is the narrow “waist” of the duplicated chromosome, where the two chromatids are most closely attached

10. LE 12-4 0.5 µm Chromosome duplication (including DNA synthesis)
Centromere
Sister
chromatids
Separation
of sister
chromatids
Centromeres
Sister chromatids

11. Eukaryotic cell division consists of:
Mitosis, the division of 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

12. 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)
Interphase (about 90% of the cell cycle) can be divided into subphases:
G1 phase (“first gap”)
S phase (“synthesis”)
G2 phase (“second gap”)

13. INTERPHASE S (DNA synthesis)
LE 12-5
INTERPHASE S
(DNA synthesis) G1
Cytokinesis
Mitosis G2
MITOTIC
(M) PHASE

15. The Mitotic Spindle: A Closer Look
The mitotic spindle is an apparatus of microtubules that controls chromosome movement during mitosis
Assembly of spindle microtubules begins in the centrosome, the microtubule organizing center
The centrosome replicates, forming two centrosomes that migrate to opposite ends of the cell, as spindle microtubules grow out from them
An aster (a radial array of short microtubules) extends from each centrosome

16. LE 12-7 Aster Centrosome Sister chromatids Microtubules Chromosomes
Metaphase
plate
Kineto-
chores
Overlapping
nonkinetochore
microtubules
Kinetochore
microtubules
Centrosome
1 µm
0.5 µm

17. In anaphase, sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell
The microtubules shorten by depolymerizing at their kinetochore ends

18. Chromosome movement Kinetochore Tubulin subunits Motor Microtubule
LE 12-8b
Chromosome
movement
Kinetochore
Tubulin
subunits
Motor
protein
Microtubule
Chromosome

19. Cytokinesis: A Closer Look
In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow
In plant cells, a cell plate forms during cytokinesis
Animation: Cytokinesis

20. LE 12-9a
100 µm
Cleavage furrow
Contractile ring of
microfilaments
Daughter cells
Cleavage of an animal cell (SEM)

21. LE 12-9b
Vesicles
forming
cell plate
Wall of
parent cell
1 µm
Cell plate
New cell wall
Daughter cells
Cell plate formation in a plant cell (TEM)

22. LE 12-10 Chromatin condensing Nucleus Chromosomes Cell plate 10 µm
Nucleolus
Prophase. The
chromatin is condensing.
The nucleolus is beginning to disappear.
Although not yet visible in the micrograph, the mitotic spindle is starting to form.
Prometaphase. We
now see discrete chromosomes; each
consists of two identical sister chromatids. Later
in prometaphase, the
nuclear envelope 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 the cell as their kinetochore micro-
tubules shorten.
Telophase. Daughter nuclei are forming. Meanwhile, cytokinesis has started: The cell plate, which will divide the cytoplasm in two, is growing toward the perimeter of the parent cell.

23. Binary Fission
Prokaryotes (bacteria and archaea) reproduce by a type of cell division called binary fission
In binary fission, the chromosome replicates (beginning at the origin of replication), and the two daughter chromosomes actively move apart

24. Chromosome replication begins. Soon thereafter,
LE 12-11_1
Cell wall
Origin of
replication
Plasma
membrane
E. coli cell
Bacterial
chromosome
Chromosome replication begins. Soon thereafter,
one copy of the origin moves rapidly toward the other end of the cell.
Two copies
of origin

25. Chromosome replication begins. Soon thereafter,
LE 12-11_2
Cell wall
Origin of
replication
Plasma
membrane
E. coli cell
Bacterial
chromosome
Chromosome replication begins. Soon thereafter,
one copy of the origin moves rapidly toward the other end of the cell.
Two copies
of origin
Origin
Origin
Replication continues. One copy of the origin is now at each end of the cell.

26. LE 12-11_3 Cell wall Origin of replication Plasma membrane
E. coli cell
Bacterial
chromosome
Chromosome replication begins.
Soon thereafter,
one copy of the origin moves rapidly toward the other end of the cell.
Two copies
of origin
Origin
Origin
Replication continues. One copy of the origin is now at each end of the cell.
Replication finishes.
The plasma membrane grows inward, and
new cell wall is deposited.
Two daughter
cells result.

27. 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 clock has specific checkpoints where the cell cycle stops until a go-ahead signal is received

28. This man has cancer of the mouth.

29. http://science. education. nih

30. What is Cancer? Cancer means uncontrolled cell growth
The body needs to keep cell growth = cell death
Cell cycle checkpoints kill mutated or old cells

31. Cell Cycle Checkpoints
Mutated cancer cells skip cell cycle checkpoints at the end of:
G1: Is the cell big enough?
G2: Is the cell ready for mitosis?
Mitosis: Does the body need more cells?

32. G1 Phase S Phase Mitosis Cytokinesis G2 Phase
The cell cycle has traffic lights that serve as checkpoints
Is the cell big enough?
G1 Phase
S Phase
Mitosis
Cytokinesis
G2 Phase
Does the body need more cells?
Is the cell ready for mitosis?

33. Cancer is caused when the checkpoints are broken and the cell cycle keeps going without stopping
G1 Phase
S Phase
Mitosis
Cytokinesis
G2 Phase

34. What are the types of cancer?
*Any part of the body can be cancerous
Skin cancer
Lung cancer
Breast cancer
Testicular cancer
Colon cancer
Liver cancer
Brain cancer
Lung Cancer
Brain Cancer

36. How do you get cancer? How can you get cancer?
Getting hit in the breast? NO
Having unprotected sex?
Smoking?
YES
Being in the sun too long?

37. Why is cancer so deadly? *
1) Mutated cells beat the cell cycle checkpoints and keep dividing
2) They form tumors which then stop your body parts from functioning normally
3) Angiogensis – the tumors hijack blood vessels to keep them alive
4) Metastisis – the cells from the tumor travel and infect other parts of your body *

38. Cancer Animation

39. Here is the development of colon cancer.

40. Why is Cancer so Hard to Cure?
It is a silent killer, by the time it is found it is already to late
2) Chemo/Radiation therapy can kill cancer cells, but is hard on patients
3) If one cancer cell survives, or travels, cancer will come back

41. Can cancer be prevented?
Cancer is not contagious.
There is no guaranteed way to prevent cancer, people can reduce their risk (chance) of developing cancer by:
A) not using tobacco products
B) choosing foods with less fat and eating more vegetables, fruits, and whole grains
C) exercising regularly and maintaining a lean weight
D) avoiding the harmful rays of the sun, using sunblock, and wearing clothing that protects the skin

42. G1 checkpoint Control system S G1 G2 M M checkpoint G2 checkpoint
LE 12-14
G1 checkpoint
Control
system S G1 G2 M
M checkpoint
G2 checkpoint

43. For many cells, the G1 checkpoint seems to be the most important one
If a cell receives a go-ahead signal at the G1 checkpoint, it will usually complete the S, G2, and M phases and divide
If the cell does not receive the go-ahead signal, it will exit the cycle, switching into a nondividing state called the G0 phase

44. LE 12-15 G0
G1 checkpoint G1 G1
If a cell receives a go-ahead signal at the G1 checkpoint, the cell continues on in the cell cycle.
If a cell does not receive a go-ahead signal at the G1 checkpoint, the cell exits the cell cycle and goes into G0, a nondividing state.

45. The Cell Cycle Clock: Cyclins and Cyclin-Dependent Kinases
Two types of regulatory proteins are involved in cell cycle control: cyclins and cyclin-dependent kinases (Cdks)
The activity of cyclins and Cdks fluctuates during the cell cycle

46. Relative concentration
LE 12-16a M G1 S G2 M G1 S G2 M
MPF activity
Cyclin
Relative concentration
Time
Fluctuation of MPF activity and cyclin concentration
during the cell cycle

47. Molecular mechanisms that help regulate the cell cycle
LE 12-16b G1
Cyclin S
Cdk
Degraded
cyclin M G2
accumulation G2
checkpoint
Cdk
Cyclin is
degraded
Cyclin
MPF
Molecular mechanisms that help regulate the cell cycle

48. Stop and Go Signs: Internal and External Signals at the Checkpoints
An example of an internal signal is that kinetochores not attached to spindle microtubules send a molecular signal that delays anaphase
Some external signals are growth factors, proteins released by certain cells that stimulate other cells to divide
For example, platelet-derived growth factor (PDGF) stimulates the division of human fibroblast cells in culture

49. LE 12-17 Scalpels Petri plate Without PDGF With PDGF Without PDGF
10 mm

50. Another example of external signals is density-dependent inhibition, in which crowded cells stop dividing
Most animal cells also exhibit anchorage dependence, in which they must be attached to a substratum in order to divide

51. Cells anchor to dish surface and divide (anchorage dependence).
LE 12-18a
Cells anchor to dish surface and
divide (anchorage dependence).
When cells have formed a complete
single layer, they stop dividing
(density-dependent inhibition).
If some cells are scraped away, the
remaining cells divide to fill the gap and
then stop (density-dependent inhibition).
25 µm
Normal mammalian cells

52. Cancer cells exhibit neither density-dependent inhibition nor anchorage dependence

53. Cancer cells do not exhibit anchorage dependence
LE 12-18b
Cancer cells do not exhibit
anchorage dependence
or density-dependent inhibition.
25 µm
Cancer cells

54. Loss of Cell Cycle Controls in Cancer Cells
Cancer cells do not respond normally to the body’s control mechanisms
Cancer cells form tumors, masses of abnormal cells within otherwise normal tissue
If abnormal cells remain at the original site, the lump is called a benign tumor
Malignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body, where they may form secondary tumors

55. LE 12-19 Lymph vessel Tumor Blood vessel Glandular tissue Metastatic
Cancer cell
A tumor grows from a
single cancer cell.
Cancer cells invade
neighboring tissue.
Cancer cells spread
through lymph and
blood vessels to
other parts of the
body.
A small percentage
of cancer cells may
survive and establish
a new tumor in another
part of the body.

56. Mitosis vs. Meiosis