129
CHAPTER FOUR
Cellular Metabolism
C
C
AT
C
CG
G
C
C
G
C
G
A
A
T
T
CG
C
AT
AT
A
T
AT
AT
AT
A
T
Newly formed
DNA molecules
Region of
replication
Original DNA
molecule
AT
AT
AT
AT
C
G
G
G
G
G
G
G
G
G
CC
A
C
C
CG
Restriction
checkpoint
G
1
phase:
cell growth
S phase:
genetic
material
replicates
Apoptosis
Remain
specialized
Proceed
to division
S
G
2
phase
Prophase
Metaphase
Anaphase
Telophase
M
i
t
o
s
i
s
I
n
t
e
r
p
h
a
s
e
Cytokinesis
G2
G1
FIGURE 4.20
When DNA replicates, its original strands
separate locally. A new strand of complementary nucleotides
forms along each original strand. The dots represent hydrogen
bonds. Three hydrogen bonds form between C and G and two
form between A and T. The inset traces DNA replication on a
symbolic single chromosome through the cell cycle.
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