Transcript Cell Division

Cell Division
“All cells come from pre-existing cells.”
HOW?
PREVIEW VIDEO
MITOSIS
Mitosis – division of
somatic cells.
In higher organisms,
mitosis only occurs in
somatic cells such as
liver, kidney, and
skin.
Mitosis does not
occur in sex cells
(sperm and egg).
Mitosis
WHY MITOSIS?
1.
Grow.
2.
Repair and replace.
WHAT ARE CHROMOSOMES?
Chromosomes come in linked pairs
called chromatids.
These are held together at a centromere.
CHROMATIDS
CENTROMERE
What does mitosis look like?
Video of mitosis
Understanding mitosis
requires an understanding
of the stages of mitosis.
What are the stages of mitosis?
INTERPHASE
A. Normal cell function.
B. DNA is copied.
Plant and animal
cells in interphase.
Interphase
Chromatid
Chromatid
Centromere
DNA Synthesis
Chromosome
before DNA
Synthesis
Chromosome
after DNA
Synthesis
PROPHASE
A. Nuclear membrane dissolves.
Easier to move when cells divide!
B. Chromosomes condense.
CHROMATIN
condenses into
CHROMOSOMES
Prophase
C. SPINDLE FIBERS attach to the
CENTROMERE of each chromosome.
Prophase
Plant and animal cells
in prophase.
Metaphase
Chromosomes line up in middle of the cell.
Plant and animal cells
in metaphase.
Anaphase
A. Spindle fibers pull chromatids apart.
B. Chromatids move to opposite ends.
Plant and animal cells
in Anaphase.
Telophase and Cytokinesis
A. Chromosomes reach opposite ends.
B. Nuclear membrane is remade.
C. Cytokinesis – cell membrane pinches in
to form two new cells.
In plants, cell wall forms between both cells.
Telephase and Cytokinesis
Plant and animal cells
in Telophase.
Cytokinesis
A good way of remembering the
stages of mitosis is:
I
Prefer
Mangoes
After
Tea
OVERALL GOAL OF MITOSIS
Divide one cell into two cells.
Keep the chromosome number the same.
Mitosis
ANIMATION OF PLANT CELL MITOSIS – click on “Plant Cell Mitosis” on left
MITOSIS IN NEWT LUNG CELLS – click on “Live Animal Mitosis” on left
MITOSIS VIDEO QUIZ
PLANT CELL
INTERPHASE
PLANT CELL
PROPHASE
PLANT CELL
METAPHASE
PLANT CELL
ANAPHASE
PLANT CELL
TELOPHASE
ANIMAL CELL
INTERPHASE
ANIMAL CELL
PROPHASE
ANIMAL CELL
METAPHASE
ANIMAL CELL
ANAPHASE
ANIMAL CELL
TELOPHASE
WHEN DOES MITOSIS OCCUR?
G1 – normal cell functions
S – DNA is copied
G2 – normal cell functions
Cell Cycle Movie
In otherwords: Cells do a lot more than just reproduce!
HOW LONG DOES MITOSIS TAKE?
Bacteria – Every 20 minutes!
Human Kidney cells – 24 hours
Human Nerve cells – Don’t divide after birth
Onion Root Tip - 720 minutes (12 hours)
HOW LONG DOES MITOSIS TAKE?
When does mitosis occur?
All through life!
When during life does mitosis
occur the fastest?
Before birth.
# of cells in a phase 720 = Total time spent
*
Total # of cells
in that phase
Cancer – When Cell Cycle Doesn’t Stop
Cell Cycle Animation
Cell Cycle doesn’t always keep going
Checkpoints to make sure cycle is done
correctly.
Checkpoint
Checkpoint
Checkpoint
What happens during a checkpoint?
Checkpoint #1 – During G1, Cdk checks if cell
has grown enough.
Checkpoint #2 – End of G2, p27 checks if
chromosomes have been copied.
Checkpoint #3 – During metaphase, p53
checks if chromosomes are lined up in middle of
cell. Mutated p53 is most frequent cause of
cancer.
APOPTOSIS
If cell is too damaged, apoptosis or
“programmed cell death” occurs.
What organelle might be involved in this
process?
LYSOSOME
APOPTOSIS
When else during life
does “programmed
cell death” occur?
Prior to birth
CANCER
If cell cycle isn’t performed correctly, cells
become cancerous.
CANCER VIDEO