1. Instructions
Hi guys! I hope you have a great Thanksgiving weekend, your homework is to write Slides 2 through 25. Including the pictures on Slide 4, 6, 8. See you on Monday

2. Functions of Cell Division
Replacement of lost or damaged cells
Growth—multicellular organisms grow and develop from single cell (fertilize egg)
Cell Reproduction

3. Prokaryotes Genes usually carried on a single circular DNA molecule
DNA has a few proteins and is attached to the plasma membrane at one point
DNA not bounded by membrane (nucleoid region)
Cells divide by binary fission

4. Binary Fission
Before dividing, an exact copy of the chromosome is made
The attachment point divides so the 2 new chromosomes are attached at separate parts of the membrane
The cell elongates and a new plasma membrane is added and the attachment points move apart
The plasma membrane and new cell wall pinch through the cell, separating the 2 chromosomes into two new, identical cells
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5. Cell Division in Eukaryotes
In eukaryotes, cell division occurs in two major stages.
The first stage, division of the cell nucleus, is called mitosis.
The second stage, division of the cell cytoplasm, is called cytokinesis.
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Chromosomes
Genetic information is passed from one generation to the next on chromosomes.
Before cell division, each chromosome is duplicated, or copied.
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Chromosomes
Each chromosome consists of two identical “sister” chromatids.
Each pair of chromatids is attached at an area called the centromere.
Photo Credit: © Gunther F. Bahr/AFIP/Stone
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Chromosomes
When the cell divides, the chromatids separate.
Each new cell gets one chromatid.
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The Cell Cycle
The cell cycle is the series of events that cells go through as they grow and divide.
Interphase is the period of growth that occurs between cell divisions.
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During the Cell Cycle
a cell grows
prepares for division
divides to form two daughter cells, each of which begins the cycle again
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The Cell Cycle
The cell cycle consists of four phases:
G1 (First Gap Phase)
S Phase
G2 (Second Gap Phase)
M Phase
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12. Events of the Cell Cycle
During G1 phase (First Gap Phase)
the cell increases in size
synthesizes new proteins and organelles
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13. Events of the Cell Cycle
During the S phase,
chromosomes are replicated
DNA synthesis takes place
Once a cell enters the S phase, it usually completes the rest of the cell cycle.
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14. Events of the Cell Cycle
The G2 phase (Second Gap Phase)
organelles and molecules required for cell division are produced
Once G2 is complete, the cell is ready to start the M phase—Mitosis
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Mitosis
Mitosis
Biologists divide the events of mitosis into four phases:
Prophase
Metaphase
Anaphase
Telophase
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16. Prophase Prophase is the first and longest phase of mitosis.
The centrioles separate and take up positions on opposite sides of the nucleus.

17. Prophase The centrioles lie in a region called the centrosome.
The centrosome helps to organize the spindle, a fanlike microtubule structure that helps separate the chromosomes.

18. Prophase Chromatin condenses into chromosomes.
The centrioles separate and a spindle begins to form.
The nuclear envelope breaks down.

19. Prophase

20. Metaphase Centrosomes at opposite poles of cell
The chromosomes line up across the center of the cell.
Centromeres of all chromosomes are aligned with one another, and sister chromatids straddle metaphase plate
Microtubules connect the centromere of each chromosome to the poles of the spindle.
Mitotic spindle completely
formed

21. Metaphase

22. Anaphase The sister chromatids separate into individual chromosomes.
The chromosomes continue to move until they have separated into two groups.

23. Anaphase

24. Telophase and Cytokinesis
Daughter nuclei form at two poles of cell
A new nuclear envelope forms around each cluster of chromosomes.
Chromosomes gather at opposite ends of the cell and uncoil back into chromatin
Mitotic spindle disappears
Nucleolus reforms

25. Telophase

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Cytokinesis
During cytokinesis, the cytoplasm pinches in half.
Process overlaps with telophase of mitosis
Each daughter cell has an identical set of duplicate chromosomes
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27. Cytokinesis Occurs differently in plants and animals
Cleavage furrow forms in animal cells
Cell plate forms in plant cells
Cell Plate
Cleavage furrow

28. Cytokinesis
Figure 8.9a
Figure 8.9b

29. Cell Division
Quiz
Wiz

30. Copyright Pearson Prentice Hall
The series of events that cells go through as they grow and divide is called
the cell cycle.
mitosis.
interphase.
cytokinesis.
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31. Copyright Pearson Prentice Hall
The phase of mitosis during which the chromosomes line up across the center of the cell is
prophase.
metaphase.
anaphase.
telophase.
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Cytokinesis usually occurs
at the same time as telophase.
after telophase.
during interphase.
during anaphase
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DNA replication takes place during the
G2 phase of the cell cycle.
G1 phase of the cell cycle.
S phase of the cell cycle.
M phase of the cell cycle.
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During mitosis, “sister” chromatids separate from one another during
telophase.
interphase.
anaphase.
metaphase.
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35. END OF SECTION

36. Cell Cycle Regulation
Ch. 10
Biology
Ms. Haut

37. Controls on Cell Division
Experiments show that normal cells will reproduce until they come into contact with other cells.
When cells come into contact with other cells, they respond by not growing.
This demonstrates that controls on cell growth and division can be turned on and off.
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38. Controls on Cell Division
Contact Inhibition
Cells attach to dish surface and divide.
When cells have formed a complete single layer, they stop dividing (contact inhibition).
Cells in a petri dish will continue to grow until they come into contact with other cells.
If some cells are scraped away, the remaining cells divide to fill the dish with a single layer and then stop (contact inhibition).
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Cell Cycle Regulators
The cell cycle is regulated by a specific protein.
The amount of this protein in the cell rises and falls in time with the cell cycle.
Scientists called this protein cyclin because it seemed to regulate the cell cycle.
Cyclins regulate the timing of the cell cycle in eukaryotic cells.
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40. Copyright Pearson Prentice Hall
Internal Regulators 
Proteins that respond to events inside the cell are called internal regulators.
Internal regulators allow the cell cycle to proceed only when certain processes have happened inside the cell.
Cells do not enter into Mitosis until all chromosomes have been copied
Anaphase does not occur until all chromosomes are lined up on metaphase plate and attached to the mitotic spindle
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41. External Regulators 
Proteins that respond to events outside the cell are called external regulators.
External regulators direct cells to speed up or slow down the cell cycle.

42. External Regulators 
Growth factors are proteins that stimulate growth and division
After forming a single layer, cells have stopped dividing.
Providing an additional supply of growth factors stimulates further cell division.

43. External Regulators 
Other molecules found on the surfaces of neighboring cells can slow down or stop their cell division
Prevents excessive cell growth and keeps tissues in the body from disrupting one another

44. Uncontrolled Cell Growth
Cancer is a disorder in which some of the body's own cells lose the ability to control growth.
Cancer cells do not respond to the signals that regulate the growth of most cells.
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45. Uncontrolled Cell Growth
Cancer cells divide uncontrollably and form masses of cells called tumors that can damage the surrounding tissues.
Cancer cells may break loose from tumors and spread throughout the body, disrupting normal activities and causing serious medical problems or even death.
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46. Uncontrolled Cell Growth
Two types of tumors
Benign tumors
Grow only locally
Do not spread
Can typically be removed
Malignant tumors
Grow and invade neighboring tissues
Can break away from original tumor and spread throughout the body (metastasis)

47. Uncontrolled Cell Growth
An astonishing number of cancer cells have a defect in a gene called p53
p53 is a tumor suppressing gene found on chromosome 17
Prevents mitosis if DNA is damaged
Will activate other genes to stop cell growth or cause cell death

48. Risks of Cancer Tobacco (lung cancer, lip and mouth cancer)
Sunlight (UV radiation leading to skin cancer)
Ionizing radiation (X-rays)
Certain chemicals and other substances (asbestos, benzene, certain metals, etc.)
Some viruses and bacteria (liver cancer, lymphoma, leukemia)
Alcohol (liver cancer, breast cancer)
Poor diet, lack of physical activity, or being overweight
Growing older
Family history of cancer
www. cancer.gov

49. Cell Cycle Regulation
Quiz
Wiz

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The cell cycle is believed to be controlled by proteins called
spindles.
cyclins.
regulators.
centrosomes.
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51. Copyright Pearson Prentice Hall
Proteins that respond to events inside the cell are called
internal regulators.
external regulators.
cyclins.
growth factors.
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52. Copyright Pearson Prentice Hall
One of the functions of internal regulators is to
cause the cell to stop dividing.
prevent anaphase from occurring until all chromosomes are attached to the spindle.
trigger cancer formation.
undergo cell division randomly.
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53. Copyright Pearson Prentice Hall
One effect of an internal regulator is that a cell will not begin mitosis until
it becomes too large.
the cell’s growth is stimulated.
it is in physical contact with other cells.
all its chromosomes have been replicated.
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54. Copyright Pearson Prentice Hall
One factor common to almost all cancer cells is
a lack of cyclin.
a defect in gene p53.
exposure to tobacco smoke.
exposure to radiation.
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