Transcript 1 Mitosis-and

The Cell Cycle and Mitosis
IMPORTANCE
• 1. Growth
• 2. Tissue Repair
• 3. Means of asexual reproduction for
single celled eukaryotes.
• 4. Keeps chromosome number
constant.
Cell Cycle
• Interphase
• Mitosis
• Cytokinesis
Eukaryotic Cell Cycle
• 1. Most of cell cycle
consists of the
interphase
• 2. Mitosis describes
nuclear division
INTERPHASE (Growth Phase)
• 1. Cell grows
• 2. Chromosomes duplicate.
(Chromosomes consist of two DNA strands).
• 3. Cell prepares for
mitosis
STAGES OF MITOSIS
•
•
•
•
•
•
Mitosis= Nuclear Division
Has 4 phases
Prophase
Metaphase
Anaphase
Telophase
PROPHASE
• 1. Chromosomes
coil up and become
visible
• 2. Nuclear
membrane and
Nucleolus
disappears.
(shown by dotted line)
3. Spindle appears.
4. Centrioles move
toward poles
Early
Prophase
Late
Prophase
What has happened?
What’s a spindle?
• Made of the centriole and microtubules
(part of the cytoskeleton)
• The fibers attach to the centromere of
the chromosome and “reel them in”
• Interpretive Dance Time
METAPHASE
Chromosomes become aligned at
the equator of the spindle.
ANAPHASE
• 1. Chromatids
separate.
• 2. Two identical
groups formed.
• 3. Separated
chromatids move to
opposite poles of
the cell.
TELOPHASE
• 1. Chromosomes
uncoil and disappear
• 2. Nuclear
membrane
reappears.
• 3. In plant cells the
cell plate appears.
• Spindle fibers
dissolve
Cytokinesis (Division of
Cytoplasm)
• The cytoplasm is
divided and
produces two
daughter cells
(identical).
Animation
CRITICAL THINKING
• Human red blood cells develop in the
bone marrow from stem cells, and lose
their nucleus before maturing and being
released into the bloodstream. While
this gives a cell that can be densely
packed with hemoglobin molecules,
what are the consequences as for as
the longevity & its ability to replicate?
CRITICAL THINKING
• Lacking DNA coding, the red blood cells
will not themselves be able to replicate
• and we must rely on the stem cells in
the bone marrow to continue red blood
cell production. In addition, the red
blood cells will be limited in life span
and unable to make substantial DNAcoded repairs.
Did You Know…
• Cells do not live forever, and they will reach a point
where they will divide through mitosis, or die through
a process called apoptosis. Cancer cells are the
exception, these cells do not die and divide
uncontrollably as they crowd out healthy, productive
cells.
• Cancer can have many causes, but most are thought
to be related to carcinogens in the environment.
Carcinogens are chemicals that can damage DNA and
interfere with a cell's normal cycle, thus disrupting
the cells ability to control when and how often it
divides.