1. The Cell
Cycle

2. In the time that it
takes you to read
this sentence, your
body will have
made millions of
new cells! Making
new cells allows
you to grow and
replace cells that
have died.

3. The Life of a Cell
 Cell cycle: the life cycle
of a cell
 Cell cycle begins when the
cell is formed and ends
when the cell divides and
forms new cells
 Before a cell divides, it
must make a copy of its
DNA

4.  DNA is organized into structures
called CHROMOSOMES
 Copying chromosomes ensures that
each new cell will be an exact copy
of its parent cell

5. How does a cell make more cells?
Depends on whether it’s
prokaryotic (no nucleus)
or
eukaryotic (with nucleus)

6. Making More Prokaryotic Cells
 Prokaryotic cells are less
complex than eukaryotic
cells
 Cell division is called
“binary fission”, which
means “splitting into two
parts”
 Binary fission results in two
cells that each contain one
copy of the circle of DNA

7. Eukaryotic Cells and Their DNA
 Eukaryotic cells
are more complex
 The chromosomes
of eukaryotic cells
contain more DNA
than prokaryotic
cells

8.  Different kinds of
eukaryotes have
different numbers
of chromosomes
 Example: humans
have 46
chromosomes

9. Think “more chromosomes = better
organism”?
Not true! Humans have 46, but a lot of organisms have
more than us!
 Butterfly = 380
 Goldfish = 94
 Horse = 64
 Amoeba = 40
 Tobacco plant = 48

10.  Homologous chromosomes:
chromosomes that have the same
sequence of genes and the same
structure

11. Making More Eukaryotic Cells
 The eukaryotic cell cycle includes 3 stages:
1. Interphase: cell grows and copies its
organelles and chromosomes
2. Mitosis: complicated process of
chromosome separation
3. Cytokinesis: cell splits into two cells; these
cells are identical to each other

12. Mitosis
•Cell division occurs in a series
of stages, or phases

13. 1st: INTERPHASE
 Chromosomes are
copied (# doubles)
 Chromosomes appear
as threadlike coils
(chromatin) at the
start, but each
chromosome and its
copy (sister
chromosome) change
centromere to sister chromatids at
end of this phase

14. 2 : PROPHASE
nd
 Mitosis begins (cell
begins to divide)
 Centrioles (or poles)
appear and begin to
move to opposite sides
of cell
 Spindle fibers form
between the poles

15. 3 : METAPHASE
rd
 Chromatids (or
pairs of
chromosomes)
attach to the
spindle fibers

16. 4 : ANAPHASE
th
 Chromatids (or
pairs of
chromosomes)
separate and begin
to move to
opposite ends of
the cell

17. 5 :
th
TELOPHASE
 Two new nuclei form
 Chromosomes
appear as chromatin
(threads rather
than rods)
 Mitosis ends

18. 6 : CYTOKINESIS
th
 Cell membrane moves
inward to create two
daughter cells – each
with its own nucleus
with identical
chromosomes

19. Ways to Remember the Order of
Mitosis!
I Proposed Marriage After Tuesday’s Class.
I Picked Marigolds After Typing Class.
Can you think of any?