Cell division, also known as mitosis, allows cells to grow, repair damaged tissue, and replace old or damaged cells. It occurs through several steps: during interphase the cell makes copies of its DNA and organelles in preparation for division; next, the condensed chromosomes align in the center of the cell during metaphase and are then pulled apart during anaphase; finally, in telophase two new daughter cells form with identical DNA and cytoplasm as the original parent cell. Precise control of the cell cycle through mitosis is essential for healthy cell growth and tissue maintenance.

1. Growing and Repairing ourselves through cell division - Mitosis

2. Cell Division—Mitosis Notes
Cell Division — process by which
a cell divides into 2 new cells
• Why do cells need to divide?
1.Living things grow by
producing more cells, NOT
because each cell increases in
size
2.Repair of damaged tissue
3.If cell gets too big, it cannot
get enough nutrients into the
cell and wastes out of the cell

3. Skin cancer - the abnormal growth of
skin cells - most often develops on skin
exposed to the sun.
Cell reproduce constantly.

4. 4
Keeping Cells Identical
The instructions for
making cell parts are
in the DNA
Each cell must have
it’s own DNA

5. 5
DNA Replication
So cells need to make
a copy of the DNA
before dividing
When one of our cells
splits in two new ones
each new cell will then
it’s own copy of the
DNA
Original DNA
strand
Two new,
identical DNA
strands

6. DNA
• DNA is located in the nucleus and controls all cell activities including cell division
• When the cell does not need to divide and make more cells , DNA is found in a
Long and thread-like form called chromatin
• When the cell is getting ready to divide the DNA is found in a Doubled, coiled,
short DNA in a dividing cell is called chromosome

7. Chromatin
Duplicates
itself
Coils up into
chromosomes
•Chromatin to chromosomes illustration:
Why does DNA need to change
from chromatin to chromosome?
Easier to divide

8. • The original cell is called the parent cell; the two new
cells it divides into are called daughter cells
• Before cell divides, the cell makes copies all of its DNA,
so each daughter cell gets a complete set of information
from parent cell
• Each daughter cell is exactly like the parent cell – same
kind and number of chromosomes as the original cell
Parent Cell
2
Daughter
Cells

9. Chromosome number
•Every organism has its own specific number of
chromosomes
Examples: Human = 46 chromosomes or 23 pairs
Dog = 78 chromosomes or 39 pairs
Goldfish = 94 chromosomes or 47 pairs
Lettuce = 18 chromosomes or 9 pairs

10. • All body cells in an organism have the same kind and
number of chromosomes
Examples: Human = 46 chromosomes
Human skin cell = 46 chromosomes
Human heart cell = 46 chromosomes
Human muscle cell = 46 chromosomes
Fruit fly = 8 chromosomes
Fruit fly skin cell = 8 chromosomes
Fruit fly heart cell = 8 chromosomes
Fruit fly muscle cell = 8 chromosomes

11. Cell Cycle
Some things must happen before cells can grow
and divide

12. Interphase
• This is the time where the cell grows (makes all it
needs to do it’s job right)
• continues normal cell activities
• Makes a copy of it’s DNA as it is getting ready to
divide
• Makes a copy of the organelles inside
• So it makes sure it has 2 of everything and is ready
to divide
•The cell spends most of its life (90%) cycle in
Interphase

13. Mitosis – is what the division of cell is called
Each new cell will get it’s own nucleus, the same
number of chromosomes with mitosis
•Mitosis occurs in all the body cells
Why does mitosis occur?
So each new daughter cell
has nucleus with a complete
set of chromosomes

14. Interphase
Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

15. Anaphase—(Apart)
Prophase Metaphase—(Middle)
Telophase—(Two)Anaphase—(Apart)
• There are 4 phases in mitosis

16.  Chromosomes go from
spaghetti looking DNA to a
tight regular shape (coil up)
 Nuclear membrane disappears
 Spindle fibers form ( fibers
that will help move the
chromosomes around)
Prophase

18.  Chromosomes line up
in middle of cell
 Spindle fibers connect
to chromosomes
Metaphase—(Middle)

20.  Chromosome
copies divide
 Spindle fibers pull
chromosomes to
opposite poles
Anaphase—(Apart)

22.  Chromosomes uncoil back to
spaghetti like shape (they stay
like this in chromatin when not
dividing)
 Nuclear membranes form
 2 new nuclei are formed (one
for each cell )
 Spindle fibers disappear
 And the outer membrane of the
cell pinches ready to close
Telophase—(Two)

24. Cytokinesis — the membrane closes off after each
new cell has the chromosomes , it’s own nucleus
,cytoplasm and organelles
•After mitosis and cytokinesis,
the cell returns to Interphase
to continue to grow and
continue it’s own cell
activities and jobs until it is
time to divide again

25. Summary: Cell Cycle
Interphase Mitosis Cytokinesis
•When cells become old or damaged, they die and
are replaced with new cells
http://www.cellsalive.com/mitosis_js.htm

28. Cell Division Control
•DNA controls all cell
activities including cell
division
•Some cells lose their ability
to control their rate of cell
division – the DNA of
these cells has become
damaged or changed
(mutated)
•These super-dividing cells
form masses called tumors

29. •Benign tumors are not cancer – these cells do not
spread to other parts of the body
•Malignant tumors are cancer – these cells break
loose and can invade and destroy healthy tissue
in other parts of the body

30. •Cancer is not just one
disease, but many
diseases – over 100
different types of
cancers

31. Please: Pairs of chromosomes aPPear
in Prophase
•Make: chromomes Meet in Middle
during Metaphase
•A: chromomes are pulled Apart
during Anaphase
•T: Two cells with their own nucleus
appear in Telophase
The menmonic "Please Make A Twin" makes it easier to
remember the active phases of cell division.

32. Prophase: Metaphase:
Anaphase: Telophase: