Transcript Mitosis - Cell division

Mitosis - Cell division
http://www.youtube.com/watch?v=VGV3fv-uZYI
• Living organisms have life cycles.
• Life cycles begin with organism’s
formation, followed by growth and
development and end in death.
• Individual cells
have life cycles.
• Some cells
constantly complete
the cycle, others
take 16-20 hours or
longer.
• Cell cycle is
broken down into
sections
Interphase
• The longest part of a cell’s life cycle
• Several major things occur during
Interphase;
– The cell grows, develops.
– Organelles are duplicated.
– The DNA is copied (chromosomes
duplicated)
• The cell prepares for cell division.
• Interphase is NOT part of mitosis.
Interphase
• In Interphase,
chromatids are
duplicated.
• When the
nucleus is ready
to divide, each
duplicated
chromosome
coils into two
thickened
strands called
chromatids.
Mitosis
• Mitosis: process
in which the
nucleus divides
to form two
identical nuclei.
• Steps of Mitosis:
Prophase,
Metaphase,
Anaphase, and
Telophase.
(PMAT)
Prophase
(Prepare)
•
•
•
•
First step of mitosis
Chromatids are fully visible under a microscope
Nucleolus and nuclear membrane disintegrate
Two organelles called centrioles move to
opposite ends in the cell.
• Between the centrioles, (only in animal cells)
thin threadlike structures called spindle fibers
begin to stretch across the cell.
Metaphase (Middle)
• The chromosomes line up across the
midline of the cell.
• The centromere of each chromosome
becomes attached to the spindle fibers.
Anaphase (Apart)
• The centromere, in the
center of each pair of
chromatids, splits in half.
• The spindle fibers
shorten, pulling the pair
of chromatids apart.
• Each pair of chromatids
separate, and move to
opposite ends of the cell.
Telophase (Two nuclei form)
• Spindle fibers
disappear.
• Nuclear membrane
reappears.
• Chromosomes
begin to uncoil and
a new nucleus
forms.
Cytokinesis
• Division of the cytoplasm
• In animal cells – the cell membrane
pinches in the middle.
• In plant cells – a cell plate forms followed
by the formation of new cell walls .
• Then cells enter into Interphase to repeat
the cell cycle again.
Cytokinesis
Animal Cell
Why doesn’t a plant cell
pinch in at the sides like
an animal cell?
Plant Cell
Onion Root Tip Cells
Results of Mitosis
• Mitosis is the division of a nucleus.
• The process produces two new nuclei that
are identical to each other and to the
original nucleus.
Why does mitosis happen?
• Mitosis allows for:
– Growth
– Replacement of worn out or damaged cells
– In some organisms, it is used to produce new
organisms
Asexual Reproduction
• A new organism is produced from one
organism.
• The new organism has exactly the same
hereditary material as the parent
organism.
Asexual Reproduction in Plants
Asexual Reproduction in Animals
Budding and Regeneration
http://www.youtube.com/watch?v=489CSop00sY
http://www.youtube.com/watch?v=f7cXeWxxfD4
Prokaryotic organisms cannot
undergo mitosis (they have no
nucleus) They reproduce asexually
using fission
http://www.youtube.com/watch?v=VGV3fv-uZYI
What are the stages?
1.
2.
3.
4.
5.
6.
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Identify each stage of the cell cycle
(no cytokinesis stage)
Answers
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Metaphase
Prophase
Telophase
Interphase
Interphase
Interphase
Anaphase
Interphase
Anaphase
Interphase
11. Metaphase
12. Telophase
13. Interphase
14. Prophase
15. Interphase
16. Interphase
17. Metaphase
18. Interphase
Which stage is the
longest: Interphase