Transcript What are Chromosomes??

Mitotic Cell Division
• Involves mitosis and cytokinesis
• Picture
A. Mitosis
-Replicated chromosomes separate
B. Cytokinesis
-After replicated chromosomes separate, the
cytoplasm divides forming two cells
What are Chromosomes??
What are Chromosomes??
• Rod-like structures in the cell’s nucleus that
contain DNA…Only appear when cell is dividing
• When a cell is not dividing, DNA is in long
Chromatin
thin threads called…
• Chromosome # is different for many
organisms…
Human = 46
Fruit Fly = 8
Onion = 16
Goldfish= 94
- Not number of chromosomes, but the
information contained in them that
determines complexity
Why does mitotic cell division take
place?
• In multicellular organisms…
1. for growth
2. for tissue repair
• In simple organisms (ameba, paramecium,
hydra)…
1. reproduce asexually
Interphase and Stages of Mitotic Cell
Division
-Interphase – Not a stage in mitosis
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
-Cytokinesis
http://www.brainpop.com/science/cellularlifeandgenetics/mitosis/
Overview of Mitotic Cell Division
http://www.lpscience.fatcow.com/jwanamaker/animations/mitosis.htm
1. Interphase (IPMAT)
• 16-20 hrs
• DNA contained in
threads of Chromatin.
• DNA in Chromatin
replicates in s-stage.
• Chromosomes not
formed yet.
• When chromosomes
form in prophase, they
will be doubled…
Picture Interphase
2. Prophase (IPMAT)
• Doubled chromosomes visible.
• Each strand of doubled
chromosomes is a chromatid.
The chromatids are connected
at a region called centromere
• Centrioles start to move to
opposite poles.
• Spindle fibers (consist of a
microtubule) form between
centrioles.
• By end, nuclear membrane &
nucleolus disappear.
Prophase Picture
3. Metaphase (IPMAT)
• Chromosomes
attached to
spindle fibers at
centromere.
• Double stranded
chromosomes
line up in single
file at equator.
Picture Metaphase
4. Anaphase (IPMAT)
-Spindle fibers
shorten and pull
chromatids
apart.
-Single stranded
chromosomes
are moved to
opposite poles.
Picture Anaphase
5. Telophase (IPMAT)
-Division furrow
forms
-Single stranded
chromosomes
reach opposite
poles.
-Two new identical
nuclei form.
Division Furrow
Picture Telophase
6. Cytokinesis
-At end of mitosis, cytoplasm divides
forming 2 identical daughter cells.
Prophase
Metaphase
Anaphase
Telophase
•
When the cell is ready to divide it organizes it’s DNA
into _______________________.
1.
2.
3.
4.
Nuclei
Chromosomes
Centromeres
Chromatids
•
Why is it important to organize the DNA before
division?
Name that Phase
1.
2.
3.
4.
5.
Metaphase
Anaphase
Telophase
Cytokensis
Prophase
•
Why is this phase important?
Name that Phase
1.
2.
3.
4.
5.
Metaphase
Anaphase
Telophase
Cytokensis
Prophase
•
Why is this phase important?
Name that Phase
1.
2.
3.
4.
5.
Metaphase
Anaphase
Telophase
Cytokensis
Prophase
•
Why is this phase important?
Name that Phase
1.
2.
3.
4.
5.
Metaphase
Anaphase
Telophase
Cytokinesis
Prophase
•
Why is this phase important?
Name that Phase
1.
2.
3.
4.
5.
Metaphase
Anaphase
Telophase
Cytokensis
Prophase
•
Why is this phase important?
Animal Cell vs. Plant Cell Mitosis
Animal Cell vs. Plant Cell
Mitosis
• Basic process the same.
• No centrioles in plant cells.
• Cytokinesis in animal cells is by
a Divison Furrow, in plant cells
a Cell Plate of cellulose is
formed- will become cell wall.
Cancer
• Cells have a built-in cycle that tells
them how to grow, divide, and when to
stop dividing
• Sometimes a cell mutates and its cycle
doesn’t work as it should.
• The cell doesn’t get the signal to stop
dividing (Uncontrolled Cell Division)
DiagramCentrioles