Cell Division: Mitosis

1. Cell Division 1:
Mitosis
ppt. by Robin D. Seamon
1

2. CELL DIVISION
• dividing of cell into two daughter cells
Why do they divide?
1. growth of organism
2. repair of damaged cells
3. reproduction
2

3. LIMITS TO SIZE
As cell gets larger, it’s surface area becomes
insufficient for the inside volume increase
The cell membrane cannot take in enough
nutrients or rid the cell of wastes efficiently
3

4. CELL DIVISION
TYPES
• binary fission- in single-celled organisms, the
cell divides into two identical organisms
• mitosis- in multi-celled organisms, cells within
the organism divide for growth & repair
• meiosis- in sexual reproduction, the special sex
cells (sperm & egg) divide after recombining
DNA forming 4 gamete cells
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5. binary fission: exact copies of organisms are made
unicellular organisms use mitosis for
reproduction 5

6. mitosis: exact copies of cells are made
multicellular organisms use mitosis for
growth & repair
ANIMALS:
skin,
epithelial,
blood cells
PLANTS:
meristems
at tips of
roots/stems
6

7. meiosis
multicellular organisms use meiosis
in sexual reproduction 7

8. internal regulators- signals from cyclins
(proteins) inside the cell that control timing
external regulators- signals from outside the
cell such as injury or growth factors
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9. WHEN?
GROWTH OF ORGANISM
• multiplying cells
• about 2 trillion cell divisions every 24 hours
• (25 million per second)
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10. REPAIR
• replace lost cells due to injury, disease,
overuse
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VIDEO: How a Wound heals itself (4 min)

11. LIMITS
Cells can only divide a certain number of times
after which they commit suicide
Childhood Cell division > cell death
Adulthood Cell division = cell death
Aging Cell division < cell death
Contact with other cells stops cell growth
example: cells grown in a petri dish stop
growing after covering the bottom of the dish
11

12. CANCER
• when a body cell continues to divide
without stopping due to mutations
• Tumor- mass of cancer cells
12
VIDEO: Cancer Cells behave
differently (4 min)

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Metastasize- when cancer cells travel through
the blood or lymph system to spread to new
parts of the body

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Cancer treatments:
• Surgery- removal of cancerous cells/tumors
• Radiation therapy- treatment of the disease
by radiation of an x-ray; on the site of tumor
• Chemotherapy- uses a drug to kill newly
dividing cells in the whole body; by vein or pill
• Why nausea? Why hair loss?
• (stomach lining & hair
cells divide often)

15. 2 main stages of Cell Division:
• Mitosis
• Cytokinesis
Nucleus
• control center
• holds genetic
material
• chromosomes so
thin, they’re not
visible until cell
division
MITOSIS: THE STAGE
15

16. Chromatin
• the packaging of DNA + protein (histones)
• more compact & easier arrangement for cell
division
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17. VOCABULARY
Chromosome- short,
thick, rod-like
chromatin structures
Chromatid- each
individual strand of a
chromosome
(“chromosome kid”)
Centromere- region
where chromatids join
Chromosome
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18. CELL CYCLE
1. Interphase
2. Prophase
3. Metaphase
4. Anaphase
5. Telophase
6. Cytokinesis
I Pee on a
MAT.
C!
HINT:
VIDEO: The Immortal Cells of Henrietta Lacks (4:30)18

19. Interphase “in between”
• between divisions
• most of cell’s life
• cell gets itself ready for mitosis or meiosis
G1 (growth 1)
S (synthesis)
G2 (growth 2)
S: Copies DNA &
gets ready for
mitosis
G2:
Cell grows
too big and
gets ready
to divide
G1:
Does its job
and grows
Interphase
19
VIDEO LINK: Mitosis made super
easy (6 min)

20. DNA REPLICATION:
20

21. Some cells stop at G1 and never divide again
• called G0
• nerve, heart muscle cells, & eye cells
• …. you don’t get more
nerve cell
heart muscle
cells
eye cells21

22. Prophase “preparing”
• first step/phase of splitting the nucleus
• chromatin coils to form visible chromosomes
• centromeres hold sister chromatids together
centromere
miotic spindles
centriole
chromosomes
visible: (2 sister
chromatids
together)
22

23. Metaphase- “middle”
• chromosomes move to the middle
• spindle fiber attaches to centromere
Fibers
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24. Anaphase- “away”
• centromeres split
• sister chromatids are pulled apart to
opposite poles of the cell
Fibers
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25. Telophase “two”
• two distinct daughter cells form
ANIMAL CELL
PLANT CELL 25

26. Cytokinesis- cytoplasm divides, cell & nuclear
membranes complete
BREAK IT DOWN
cyto – cell
kinesis - movement
ANIMAL CELL PLANT CELL
26

27. VIDEO: Real Microscopic Mitosis (1:30) 27

28. Mitosis
Stages
Put
these
in the
correct
order..
28

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CELL DIFFERENTIATION

30. 30
During early development, all cells of an embryo
are identical.
Later in development, cells become specialized

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Cell differentiation- process by which cells
become specialized; allows them to perform
different functions.
• in multicellular organisms
• process by which embryonic cells become
specialized cells
• more than 250 general cell types

32. 32
embryonic stem cells- earliest cells
• Undifferentiated: do not have a specialized
function yet; they can turn into any type of cell
at this point
• Outside signals cause it to differentiate upon
need
• Because they are not specialized yet, these cells
can be used to heal wounds
• Scientists study these cells: have been able to
grow embryonic stem cells in petri dishes &
coax them to differentiate into nerve, muscle
cells, & even sperm & egg cells!

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Adult stem cells- groups of cells that differentiate
to renew & replace cells in the adult body
• More limited than embryonic stem cells
• Typically, these adult stem cells can grow into
other cells of similar tissue: bone marrow stem
cells can develop into several types of blood
cells, brain stem cells produce neurons, etc.

35. 35
Red blood cell-
develop from
adult stem cells
in bone
marrow
Neurons-
(Nerve cells)
from neural
stem cells in
our brains

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NEW RESEARCH
Potential benefits: HEALING
• Heart attacks destroy heart muscle cells
• Strokes injure brain cells
• Spinal cord injuries break connections of
nerve cells
FUTURE: Stem Cell Therapy

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ETHICS
Adult stem cells- willing donors
Embryonic stem cells- where do we get them?
• Fertility clinics & frozen embryos
Controversial: using embryonic stem cells,
destroys the embryo; using the research saves
lives… both sides argue issues of life and death

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FUTURE TECHNOLOGY?
• Some research has been shown to be able to
extract a small number of stem cells without
harming the embryo
• Other research shows promise in being able to
switch “on” certain genes to make adult stem
cells behave like embryonic stem cells.
SCIENTISTS CONTINUE TO STUDY THE
MATTER!