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The Cell Cycle
LN #14
The Cell Theory
All cells come from preexisting cells.
 Cell division has two major roles in the life
cycle of multicellular organisms.

Allows organisms to develop from a fertilized
egg to an embryo and then to an adult.
 Allows life to continue through the production
of sperm and eggs.

Eukaryotes have
chromosomes
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Chromosomes are made of
DNA and protein.
They are located in the
nucleus.
Chromosomes are visible
under the microscope only
when the cell is dividing.
When a cell is not dividing
they are in a tangled mass
called chromatin.
Number of Chromosomes

The somatic cells (all the body cells except
sperm or eggs) contain a characteristic number
of chromosomes.
Human somatic cells have 46 chromosomes.
 Human sperm and egg cells have 23
chromosomes.

Every somatic cell (body cell) in your body has
the same DNA.
 Cells are specialized and only use part of the
DNA for their specific job.

The Cell Cycle

Interphase
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Mitosis


cell grows
chromosomes duplicate
cell parts are made
90% of cell cycle time
cell division
Cytokinesis

cytoplasm divides in two
Chromosomes Duplicate
and Split
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Before the cell begins to divide the
cell makes a copy of its
chromosomes.
Duplication results in two identical
structures called sister chromatids.
When cell divides sister
Sister
chromatids are separated.
chromatids
Interphase is a
period of cell
growth and DNA
replication
Prophase Chromatid coils to form
chromosomes. Nuclear envelope is
gone. Spindle fibers move
chromosomes to the center.
Metaphase
Chromosomes
line up
in the Middle.
Anaphase
Chromosomes
are pulled
Apart.
Telophase
Two cells are
formed.
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Summary
What are chromosomes made of
 Where are chromosomes located?
 What are the different parts of the cell
cycle?
 What is mitosis?
 What are the different phases of
mitosis?
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