Download The Cell Cycle

The Cell Cycle
First, let’s talk about how DNA is
organized….
How long is our DNA?
If each nitrogen base was spread 1 mm
apart, the
h DNA ffor ONE off our cells
ll would
ld
extend from Memphis to Los Angeles!
„ The actual length is 1.8 meters
„ It’s g
got to p
pack into a nucleus so small we
can’t see it with the naked eye!
„
How is DNA packed?
DNA is packed into
chromosomes
Most of the time DNA exists
unwrapped
This is called
chromatin
Only when the cell is about to
divide does DNA coil up
P t off a chromosome
Parts
h
By the time DNA coils up
up, it has already
replicated
Sister
chromatids
centromere
Th C
The
Cellll C
Cycle
l
Basically, the life cycle of a cell
„ Like all living things
things, cells must grow and
develop
„ Two main parts of the cell cycle:
„
… Cell
growth (most of the time)
… Cell
C ll di
division
i i
O
Overview
i
off the
th Cell
C ll C
Cycle
l
Cell
division
I t h
Interphase
(cell
( ll growth)
th)
G1 stage Æ cell grows, develops, and
makes new proteins
p
„ S stage Æ DNA replicates
„ G2 stage Æ cell gets ready for mitosis
„
M stage
t
(cell
( ll di
division)
i i )
Mitosis
Mit
i Æ nucleus
l
di
divides
id
„ Cytokinesis Æ cytoplasm divides
„
Can y
you put these stages
g of
mitosis in order?
The four stages of mitosis
#1 Prophase
#3 Anaphase
#2 Metaphase
#4 Telophase
1 P
1.
Prophase
h
„
first and longest phase of mitosis where
chromosomes are formed and couple
p as
sister chromatids
#1 Prophase
1 P
1.
Prophase
h
„
first and longest phase of mitosis where
chromosomes are formed and couple
p as
sister chromatids
Nuclear membrane disintegrates
#1 Prophase
1 P
1.
Prophase
h
„
first and longest phase of mitosis where
chromosomes are formed and couple
p as
sister chromatids
Nuclear membrane disintegrates
Centrioles organize
*animal cells only*
#1 Prophase
1 P
1.
Prophase
h
„
first and longest phase of mitosis where
chromosomes are formed and couple
p as
sister chromatids
Nuclear membrane disintegrates
Centrioles organize
*animal cells only*
Spindle forms between the
centrioles
#1 Prophase
2 M
2.
Metaphase
t h
„
chromosomes line up on the equator
pulled by
p
y spindles
p
#2 Metaphase
3 A
3.
Anaphase
h
„
sister chromatids split and proceed to
opposite
pp
ends of the cell
#3 Anaphase
4 T
4.
Telophase
l h
„
two new nuclei are formed
#4 Telophase
Mit i iin action!
Mitosis
ti !
R
Remembering
b i th
the order
d
P = professional Æ best athletes come first
p in the
M = middle Æ chromosomes line up
middle
A = aged Æ breaking apart
T = twins Æ two identical nuclei
Or, you can come up with your own mnemonic device!
Some things to remember about
mitosis….
Æ Mitosis only occurs in somatic cells
((body
y cells),
), not sex cells
„ Æ Mitosis in unicellular organisms is a
means of reproduction
„
… For
all bacteria
… For some protists
… If an organism reproduces by mitosis, does it
ever die?
C t ki
Cytokinesis
i
cytoplasm from the original cell splits and
forms two new cells
„ follows telophase
„
#4 Telophase
Comparison of Cytokinesis in
Animal & Plant Cells
In plant cells:
In animal cells:
„ the cell membrane
„ a cell p
plate forms and
narrows at the center
eventually divides the
and eventually divides
cell into two daughter
i t two
into
t
daughter
d
ht
cells
ll
cells
Th cellll cycle:
The
l A summary
Wh t is
What
i a cancer?
?
„
Abnormal cell division