Transcript Cell Growth & Division

Chapter 10
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Does an animal get larger because each cell
increases in size or because it produces more of
them?
In most cases, living things grow by producing
more cells
Identify the problems caused by growth of cells
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Chromosomes are made of DNA (genetic
information) and proteins (histones)
The cells of every organism have a specific
number of chromosomes
◦ Fruit flies = 8, human = 46, carrots = 18
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Chromosomes are not visible in most cells
except during cell division
Each chromosome consists of two identical
sister chromatids which separate during cell
division
Each pair of chromatids is attached in an area
called the centromere
Please use headphones.
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The larger a cell becomes, the more demands a
cell places on its DNA
◦ If extra copies of DNA are not made, an “information
crisis” would occur
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The cell also has more trouble moving nutrients
and wastes across the cell membrane
◦ Food, oxygen, water, and wastes move through the cell
membrane
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Each cell has only one set of genetic
information
◦ must be copied before cell division begins
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The first stage, division of the cell nucleus, is
called mitosis
The second stage, division of the cytoplasm, is
called cytokinesis
Reproduction by mitosis is classified as asexual
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Interphase is the period in between periods of
cell division
The cell cycle is the series of events that cells
go through as they grow and divide
During the cell cycle, a cell grows, prepares for
division, and divides to form two daughter
cells, each of which then begins the cycle again
The cell cycle consists of four phases
◦ M, S, G1, and G2
Mitosis
Mitosis
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Cytokinesis is the division of the cytoplasm
itself and usually occurs at the same time as
telophase
In most animal cells, the cytoplasm is drawn
inward until the cytoplasm is pinched into two
nearly equal parts
In plants, a structure known as the cell plate
forms midway between the divided nuclei
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Not all cells move through the cell cycle at the
same rate
The cells of the skin, digestive tract, and bone
marrow grow and divide rapidly throughout
life
How is the cell cycle regulated?
How are cancer cells different from other cells?
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Proteins called cyclins - seemed to regulate the
cell cycle
Proteins that respond to events inside the cell
are called internal regulators
External regulators respond to events outside of
the cell
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Cancer is a disorder in which some of the
body’s own cells lose the ability to control
growth
They divide uncontrollably and form masses of
cells called tumors that can damage the
surrounding tissues
Causes include smoking, radiation, and viral
infections