Download Ch 10: Cell Growth and Division

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Ch 10: Cell Growth and Division
10-1 Cell Growth
A. Limits to Cell Growth
1. In most cases, living things grow by producing
more cells.
2. There are 2 main reasons why cells divide:
a. The larger a cell gets, the more demands it
places on its DNA
b. As a cell gets larger, it has more trouble
moving enough nutrients (food) and wastes
across it’s cell membrane
3. Cell division- the process by which a cell divides
into two new daughter cells
10-2 Cell Division
A. Introduction
1. In eukaryotes, cell division occurs in two major
stages.
a. The first stage, division of the cell nucleus, is
called mitosis.
b. The second stage, division of the cell
cytoplasm, is called cytokinesis.
B. Chromosomes
1. Genetic information is passed from one generation
to the next on chromosomes.
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2. Before cell division, each chromosome is
duplicated, or copied.
3. Each chromosome consists of two identical
“sister” chromatids.
4. Each pair of chromatids is attached at an area
called the centromere.
5. When the cell divides, the chromatids separate.
6. Each new cell gets one
Draw a picture of a chromosome.
chromatid.
Label centromere, chromatid and
chromosome.
Inferring: Why is it important
that each of the sister chromatids
is identical?
A:
C. The Cell Cycle
During the cell cycle, a cell
grows, prepares for division, and
divides to form two daughter
cells. Each daughter cell then
begins the cell cycle again.
1. Cell cycle- the series of events that cells go
through as they grow and divide.
2. Interphase- the period of growth that occurs
between cell divisions.
3. The cell cycle consists of four phases:
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a. G1 (First Gap Phase)
b. S Phase
c. G2 (Second Gap Phase)
d. M Phase
D. Events of the Cell Cycle
1. During G1, the cell
a. increases in size
b. synthesizes new proteins and organelles
2. During the S phase,
a. chromosomes are replicated
b. DNA synthesis takes place
c. Once a cell enters the S phase, it usually
completes the rest of the cell cycle.
3. The G2 Phase (Second Gap Phase)
a. organelles and molecules required for cell
division are produced
b. Once G2 is complete, the cell is ready to start
the M phase—Mitosis
4. M Phase, or cell division included mitosis and
cytokinesis
a. Biologists divide the events of mitosis into
four phases: Prophase, Metaphase, Anaphase,
Telophase
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Cell Cycle  
~ Follow the prompts
 Color the phase in which most cell growth occurs
blue
 Color the phase in which DNA replication occurs
red
 Color the phase in which preparation for mitosis
occurs yellow
 Color the phase in which mitosis and cytokinesis
occur orange
Q: Which three
phases make up
interphase?
A:
E. Mitosis
1. Prophase- the
first and longest
phase of mitosis.
a. The
centrioles
separate and
take up positions on opposite sides of the
nucleus.
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b. The centrioles lie in a region called the
centrosome.
c. Centrosome- helps to organize the spindle, a
fanlike microtubule structure that helps
separate the chromosomes.
d. Chromatin condenses into chromosomes.
e. The centrioles separate and a spindle begins to
form.
f. The nuclear envelope breaks down.
2. Metaphase
a. The chromosomes line up across the center of
the cell.
b. Microtubules connect the centromere of each
chromosome to the poles of the spindle.
3. Anaphase
a. The sister chromatids separate into individual
chromosomes.
b. The chromosomes continue to move until they
have separated into two groups.
4. Telophase
a. The fourth and final phase of mitosis.
b. Chromosomes gather at opposite ends of the
cell and lose their distinct shape.
c. A new nuclear envelope forms around each
cluster of chromosomes.
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Mitosis↓↓
- Color each chromosome in prophase a different
color. Follow each of these chromosomes through
mitosis. Show this by coloring the correct structure in
each phase of mitosis.
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F. Cytokinesis
1. During cytokinesis, the cytoplasm pinches in half.
2. Each daughter cell has an identical set of duplicate
chromosomes
3. In plants, a structure known as the cell plate forms
midway between the divided nuclei.
a. The cell plate gradually develops into a
separating membrane.
b. A cell wall then begins to appear in the cell
plate.
10-3 Regulating the Cell Cycle
A. Controls on Cell Division
1. In multicellular organisms, cell growth and cell
division are carefully controlled.
2. For instance, when an injury such as a cut in the
skin occurs, cells at the edge of the cut divide
rapidly.
3. When the healing process is nearly complete, the
rate of cell division slows and returns to normal
4. This demonstrates that controls on cell growth and
division can be turned on and off.
B. Cell Cycle Regulators
1. The cell cycle is regulated by a specific protein.
2. The amount of this protein in the cell rises and
falls in time with the cell cycle.
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3. Scientists called this protein cyclin because it
seemed to regulate the cell cycle.
4. Cyclins regulate the timing of the cell cycle in
eukaryotic cells.
C. Uncontrolled Cell Growth
1. Controls on cell growth can be turned on and off
by the body
2. Cancer is a disorder in which some of the body’s
cells lose the ability to control growth
3. Cancer cells do not respond to the signals that
control the growth of most cells
4. As a result, cancer cells divide uncontrollably
5. Cancer cells do not stop growing when they touch
other cells
6. Instead, they continue to grow and divide until
their supply of nutrients is used up
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In your text book on p. 249…
Answers:
1.
2.
3.
4.
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