Download Ch 8.1 Notes

Cell Division and Reproduction
Chapter 8.1
Why do cells go through
cell division?
• To grow
– Organisms grow by ADDING more cells
• To replace dead cells
– All cells will die so they need to be
replaced
• To replace damaged cells
– Cells will be damaged by injury (cut)
Definition of Cell Division
• Cell division is the
process of one cell
dividing into two
identical daughter
cells
DNA - Hereditary Material
• DNA is stored in a eukaryotic cells nucleus
– Plant cells
– Animal cells
What is Chromatin?
• Loose (stringy)
DNA in a cells
nucleus is called
chromatin
• DNA before cell
division
• DNA ‘hanging out’
Chromosome doubles
• Chromatin
condenses
(shrinks up) and
doubles just before
cell division
– This forms a
chromosome (X).
X
X
What is a Chromosome?
• A chromosome is a
structure made up of
DNA and protein in
the nucleus of a
eukaryotic cell
Cell Cycle
• The cell cycle is the period of time from
the beginning of one cell division to the
beginning of the next.
• The cell cycle has 3 parts:
– Interphase
– Mitosis
– Cytokinesis
See cycle on page 155
1. Interphase
• First part of the cell cycle
• Time in between cell divisions
– Cell is on vacation
• Longest phase. Most time is spent in
interphase
• At end, chromatin (stringy) doubles into
a chromosome (X)
Mitosis
• Second part of the cell cycle
• Makes 2 new identical nuclei
• Has 4 steps:
– Prophase
– Metaphase
– Anaphase
– Telophase
2. Prophase
• First step of mitosis
• Chromatin in nucleus coils into
chromosomes (X’s)
• Nuclear membrane begins to disappear
3. Metaphase
• Second step of mitosis
• Chromosomes line up in the middle of
the cell
• Spindle fibers attach to the
chromosomes
4. Anaphase
• Third step of mitosis
• Chromosomes separate and begin to
move to opposite ends of the cell
5. Telophase
• Final step of mitosis
• Two new nuclei form around the
separated chromosomes
• Chromosomes unwind to form
chromatin
• Mitosis ends
6. Cytokinesis
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Final part of the cell cycle
Makes 2 new identical daughter cells
Shortest phase
END of the cell cycle
Cell Cycle
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Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Mitosis
Cell Cycle Mnemonic
• Write a mnemonic for cell division
• (Ex. King Henry Died By Drinking
Chocolate Milk.)
• I
• P
• M
Add a COLORED
• A
picture
• T
• C
Cell Cycle Mnemonic
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I
Played
Music
At
The
Concert