Biology
Unit 8 – Cell Division
Notes #1 (Chapter 5)
Cell Division
• For cells, bigger is not better
• As cells get bigger, volume increases faster
than surface area
– This makes it difficult for the cell to take in
enough nutrients and get rid wastes efficiently
• When a cell reaches its max size, the
nucleus initiates cell division
Results of Cell Division
The cell cycle is important for:
•reproduction in some organisms
– asexual reproduction = identical offspring
• Regeneration (ex – sea star)
• Budding
• Fission
•growth in multicellular organisms
– Cell differentiation
•Repair replacement of worn out or damaged
cells, and repair of damaged tissues.
The Cell Cycle (cont.)
• Most cells in an organism go through a
cycle of growth, development, and
division called the cell cycle.
• There are two
main phases in
the cell cycle—
interphase and
the mitotic phase.
Part 1 -Interphase
Interphase occurs in three stages: G1, S,
and G2, and takes up 90% of the time of
the cell cycle
• G1 (gap 1)
– Period of growth, DNA = chromatin
• S (synthesis)
– Chromosomes replicate
Part 1-Interphase
– The cell’s DNA is
copied during the S
stage and is arranged
as pairs of identical
chromosomes called
sister chromatids.
– Sister chromatids are
held together by a
structure called the
centromere.
• G2 (gap 2) Cell
creates organelles
The Mitotic Phase
During mitosis,
the contents of
the nucleus divide,
forming two identical
nuclei.
The Mitotic Phase (cont.)
The Mitotic Phase (cont.)
The Mitotic Phase (cont.)
The Mitotic Phase (cont.)
The Mitotic Phase (cont.)
In cytokinesis, the cytoplasm divides
(cell membrane folds in) and forms two
new daughter cells.
Mitosis
Name that Stage!
Hint:
Chromosomes
are aligned in
middle of cell
Name that Stage!
Hint:
Cell plate is
splitting the cell
Name that Stage!
Hint:
Two normal
looking nuclei of
two cells
Name that Stage!
Hint:
Chromosomes
are forming and
the nucleus is
gone
Name that Stage!
Hint:
Chromatids are
being pulled
apart
1)
In order, name the 5 stages of the cell cycle.
2)
During which interphase stage do organelles replicate?
3)
What do you call the division of the cell’s cytoplasm ?
4)
During which interphase stage is DNA created?
5)
During which stage do spindle fibers form?
6)
During which stage are chromosomes aligned in the middle?
7)
During which stage are chromatids separated?
8)
During which stage does the nucleus dissolve?
9)
What is the result of mitosis?
Review
10) http://www.biology.arizona.edu/cell_bio/activities/cell
_cycle/36m.html
1) In order, name the 5 stages of the cell cycle.
– Interphase, Prophase, Metaphase, Anaphase, Telophase
2) During which interphase stage do organelles replicate?
– G1
3) What do you call the division of the cell’s cytoplasm?
– Cytokineses
4) During which interphase stage is DNA created?
– S
5) During which stage do spindle fibers form?
– Prophase
6) During which stage are chromosomes aligned in the middle?
– Metaphase
7) During which stage are chromatids separated?
– Anaphase
8) During which stage does the nucleus dissolve?
– Prophase
9) What is the result of mitosis?
– 2 identical (daughter) diploid cells