The Cell Cycle

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The Cell Cycle
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Cell Growth Reproduction
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Section 8.2 Summary pages 201 - 210
Cell Reproduction

• Cell division is the process by which new cells
  are produced from one cell.

• Cell division results in two cells that are
  identical to the original, parent cell.

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Section 8.2 Summary pages 201 - 210
The discovery of chromosomes

• Chromosomes are the carriers of the genetic
  material that is copied and passed from
  generation to generation of cells.

• Accurate transmission of chromosomes during cell
  division is critical.

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Section 8.2 Summary pages 201 - 210
The structure of eukaryotic chromosomes
Sister chromatids
Centromere
Continued coiling within supercoil
Supercoil within chromosome
Chromosome
DNA
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Section 8.2 Summary pages 201 - 210
The Cell Cycle

• The cell cycle is the sequence of growth and
  division of a cell.

• The majority of a cells life is spent in the
  growth period known as interphase.

Interphase
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Section 8.2 Summary pages 201 - 210
Interphase A Busy Time

• Interphase, the busiest phase of the cell cycle,
  is divided into three parts.

Interphase
DNA synthesis and replication
Centrioles replicate cell prepares for division
Rapid growth and metabolic activity
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Section 8.2 Summary pages 201 - 210
The Cell Cycle

• Following interphase, a cell enters its period of
  nuclear division called mitosis.

• Following mitosis, the cytoplasm divides,
  separating the two daughter cells.

Mitosis
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Section 8.2 Summary pages 201 - 210
The Phases of Mitosis

• The four phases of mitosis are prophase,
  metaphase, anaphase, and telophase.

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Section 8.2 Summary pages 201 - 210
Prophase The first phase of mitosis

• During prophase, the chromatin coils to form
  visible chromosomes.

Spindle fibers
Disappearing nuclear envelope
Doubled chromosome
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Section 8.2 Summary pages 201 - 210
Prophase The first phase of mitosis

• The two halves of the doubled structure are
  called sister chromatids.

Sister chromatids
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Section 8.2 Summary pages 201 - 210
Prophase The first phase of mitosis

• Sister chromatids are held together by a
  structure called a centromere, which plays a role
  in chromosome movement during mitosis.

Centromere
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Section 8.2 Summary pages 201 - 210
Metaphase The second stage of mitosis

• During metaphase, the chromosomes move to the
  equator of the spindle.

Centromere
Sister chromatids
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Section 8.2 Summary pages 201 - 210
Anaphase The third phase of mitosis

• During anaphase, the centromeres split and the
  sister chromatids are pulled apart to opposite
  poles of the cell.

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Section 8.2 Summary pages 201 - 210
Telophase The fourth phase of mitosis

• During telophase, two distinct daughter cells are
  formed. The cells separate as the cell cycle
  proceeds into the next interphase.

Nuclear envelope reappears
Two daughter cells are formed
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Section 8.2 Summary pages 201 - 210
Cytokinesis

• Following telophase, the cells cytoplasm divides
  in a process called cytokinesis.

• Cytokinesis differs between plants and animals.

• Toward the end of telophase in animal cells, the
  plasma membrane pinches in along the equator.

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Section 8.2 Summary pages 201 - 210
Cytokinesis

• Plant cells have a rigid cell wall, so the plasma
  membrane does not pinch in.

• A structure known as the cell plate is laid down
  across the cells equator.

• A cell membrane forms around each cell, and new
  cell walls form on each side of the cell plate
  until separation is complete.

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Section 8.2 Summary pages 201 - 210
Results of Mitosis

• When mitosis is complete, unicellular organisms
  remain as single cells.

• In multicellular organisms, cell growth and
  reproduction result in groups of cells that work
  together as tissue to perform a specific function.

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Section 8.2 Summary pages 201 - 210
Results of Mitosis

• Tissues organize in various combinations to form
  organs that perform more complex roles within the
  organism.

• Multiple organs that work together form an organ
  system.

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Questions
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Section 2 Check
Question 1
Question 1
The stringy structures in the cell nucleus
that contain DNA are __________.
A. centromeres
B. chromosomes
C. genes
D. chlorophylls
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Section 2 Check
Question 2
Look at the diagram and identify the stage
of mitosis that is depicted.
Centromere
Sister chromatids
C. anaphase
A. prophase
D. telophase
B. metaphase
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Section 2 Check
Question 3
What is the process by which a cell's
cytoplasm divides?
A. cytokinesis
B. telekinesis
C. meiosis
D. mitosis
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Section 2 Check
Question 4
In multicellular organisms, groups of cells
that work together to perform a specific function
are called __________.
A. organ systems
B. organs
C. tissues
D. cell cycles
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Control of the Cell Cycle
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Section 8.3 Summary pages 211 - 213
Proteins and enzymes control the cell cycle

• The cell cycle is controlled by proteins called
  cyclins and a set of enzymes that attach to the
  cyclin and become activated.

• Occasionally, cells lose control of the cell
  cycle.

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Section 8.3 Summary pages 211 - 213
Normal Control of the Cell Cycle

• This uncontrolled dividing of cells can result
  from the failure to produce certain enzymes, the
  overproduction of enzymes, or the production of
  other enzymes at the wrong time.

• Cancer is a malignant growth resulting from
  uncontrolled cell division.

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Section 8.3 Summary pages 211 - 213
Cancer A mistake in the Cell Cycle

• Currently, scientists consider cancer to be a
  result of changes in one or more of the genes
  that produce substances that are involved in
  controlling the cell cycle.

• Cancerous cells form masses of tissue called
  tumors that deprive normal cells of nutrients.

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Section 8.3 Summary pages 211 - 213
Cancer A mistake in the Cell Cycle

• In later stages, cancer cells enter the
  circulatory system and spread throughout the
  body, a process called metastasis, forming new
  tumors that disrupt the function of organs, organ
  systems, and ultimately, the organism.

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Section 8.3 Summary pages 211 - 213
The causes of cancer

• The causes of cancer are difficult to pinpoint
  because both genetic and environmental factors
  are involved.

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Section 8.3 Summary pages 211 - 213
The causes of cancer

• Environmental factors, such as cigarette smoke,
  air and water pollution, and exposure to
  ultraviolet radiation from the sun, are all known
  to damage the genes that control the cell cycle.

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Section 8.3 Summary pages 211 - 213
The causes of cancer

• Cancer may also be caused by viral infections
  that damage the genes.

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Chapter 8 Questions
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Chapter Assessment
Question 3
Magnification of a plant cell reveals centromeres
that have split and sister chromatids being
pulled to opposite poles of the cell. This cell
is in which phase of mitosis?
A. prophase
B. metaphase
C. anaphase
D. telophase
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Chapter Assessment
Question 4
Which phase of mitosis is depicted in this
diagram?
Spindle Fibers
Doubled chromosome
Disappearing nuclear envelope
C. anaphase
A. prophase
D. telophase
B. metaphase
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Chapter Assessment
Question 5
What is the term used for the period of the cell
cycle represented by the red arrow in this graph?
A. prophase
DNA synthesis and replication
B. metaphase
Centrioles replicate cell prepares for division
Rapid growth and metabolic activity
C. centrophase
D. interphase
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Chapter Assessment
Question 6
What is the level of organization that is missing
in this diagram?
Organ
Cell
Organ System
Organism
?
(muscle cell)
(stomach)
(digestive tissue)
(Florida Panther)
C. tissue
A. mass
B. cluster
D. cycle
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Chapter Assessment
Question 7
Which structure represents a cell in prophase of
mitosis?
A
B
C
D
C. C
A. A
B. B
D. D