1. Cell Cycle and Mitosis

2. Cell Cycle Only a Eukaryotic Process Rate may differ depending upon:
Unicellular: asexual reproduction
Multicellular: growth and repair
Rate may differ depending upon:
Type of cell
Age of cell
External factors that affect cells
Genetics

3. Type of Cell
The function of the cell, type of tissue often determine the rate of it’s cell cycle
Fastest include: intestinal, skin, bone marrow, hair
Slowest: bone, liver, kidney

4. Age of Cell/Organism
In multicelled organisms the rate of the cell cycle can also depend upon the number of times the cell has divided, ie ‘age’
“Age” is a factor of cell division vs cell death
Young: cell division > cell death = growth
Middle: cell division = cell death
Old: cell division< cell death

5. Why can’t organisms live forever?
Cells cannot grow and divide indefinitely. At the end of chromosomes are small ‘caps’ called telomeres that help keep the DNA from uncoiling. Every time the DNA is replicated a piece of the telomere is lost. When the telomere is gone the DNA can no longer replicate and the cell dies. Interestingly, telomeres are found in the cells of multicelled organisms, but, not unicellular…what would happen if there were?

6. External Factors Factors outside of the cell or
organism can affect the cell cycle.
Cells are exposed to many environmental factors that can directly influence the control and regulation of a cell’s cycle
Examples include: Drugs, Alcohol, Smoke, Radiation, Toxins, Viruses
All of these carcinogens disrupt the cell cycle and can cause cells to divide uncontrollably forming the tumors associated with many cancers

7. Genetic Factors
Some mutations to genes can result in changes to the cell cycle.
The BRCA1 gene can cause
breast cancer
Progeria is a genetic disorder
marked by rapid aging

8. The Cell Cycle Occurs in 3 phases Interphase: preparation for division
Mitosis: nuclear division
Cytokinesis: cell division
BATMAN

9. Mitosis
Prophase
Metaphase
Anaphase
Telophase M C
NERVE/MUSCLE

10. INTERPHASE
Use to be referred to as the cell’s ‘resting phase’, however, actually a lot of activity is occurring during this time.
Approximately 80% of cell’ life is spent in interphase
Marked by 3 distinct stages:
Gap 1 (G1 ) follows cytokinesis, time of cell growth, replication of organelles (1st Checkpoint)
Synthesis(S) Replication of DNA in preparation for division
Gap 2: (G2 )growth slows, cell enzymes check DNA
(2nd Checkpoint)

11. MITOSIS
M Phase: Process that divides the nucleus containing the replicated DNA
Approximately 15% of cell’s life cycle
4 Stages
PROPHASE: “before”; replicated DNA uncoils
METAPHASE: “after”; chromosomes align (3rd Checkpoint)
ANAPHASE: “opposite”; chromosomes separate
TELOPHASE: “across”; chromosomes recoil

12. CYTOKINESIS Division of the cell Means “to move the cell”
Approximately 5% of cell’s life
Process differs in Heterotrophs(Animals) Autotrophs(Plants) due to presence of cell wall
HETEROTROPHS
AUTOTROPHS
Cell membrane
indents at cleavage
furrow and cell
is ‘pinched’ in half
The cell divides
from the center
with the
formation of cell
plate(cellulose)
and cell is ‘cut’
in half

13. CUT YOUR PIECES OUT QUICKLY
NO NEED TO CUT CLOSE TO EDGE,
JUST DON’T CUT OFF LABEL LINES OR BRACKETS

14. GROUP THEM AS AUTOTROPHIC AND HETEROTROPHIC

15. ON YOUR DESK…
ARRANGE THE DIAGRAMS
FOLLOWING THE 4 STEPS
OF MITOSIS(PMAT)
MAKE SURE TO KEEP THE
CHROMOSOMES IN THE
SAME ORIENTATION:
EAST-WEST
THEN WHEN YOU ARE SURE
YOU ARE CORRECT…
GLUE THEM INTO THE
CORRESPONDING BOXES
ON THE WORKSHEET

16. Cell Cycle : Let’s Review
Checkpoint 3
Are chromosomes aligned?
cytokinesis
Checkpoint 2: Has DNA replicated correctly?
Checkpoint 1: Have
organelles copied? Is cell
large enough to divide?

17. G0
Arresting phase where certain cells leave the cell cycle and stop dividing
Some cells, once formed, remain in G0 for the life of the organism. These cells cannot be replaced once damaged.
Examples: Nerve and Muscle
Some cells enter an extended period of G0 , however, can be replaced overtime.
Examples: Liver and Kidney

18. Steps of Mitosis

19. PROPHASE Heterotroph/Animal Autotroph/Plant
Centrosome duplicates and move to opposite poles
Centrioles, in centrosome , form the mitotic spindle
Duplicated chromosomes, called chromatids, are held together by centromere
Nuclear membrane and nucleolus begin to breakdown
Heterotroph/Animal
Autotroph/Plant
NO CENTRIOLES in PLANT CELLS
centrioles
centrosome
sister chromatids
centromere

20. METAPHASE Heterotroph/Animal Autotroph/Plant
Spindle fibers attach to centromere and maneuver sister chromatids to
central plane of the cell
Heterotroph/Animal
Autotroph/Plant
Mitotic Spindle
Kineticore
fibers
Polar fibers

21. ANAPHASE Heterotroph/Animal Autotroph/Plant
Spindle fibers are drawn into the centriole pulling apart the two sister
chromatids. At this point they are referred to as chromosomes again.
Heterotroph/Animal
Autotroph/Plant
No Centriole in Plant

22. TELOPHASE Heterotroph/Animal Autotroph/Plant
Nuclear envelope and nucleolus reform around chromosomes
Mitotic spindle breaks down
Cytokinesis begins
Heterotroph/Animal
Autotroph/Plant
Cleavage furrow forms cell is
pinched in half
Cell plate forms from center and
cell is cut in half