This chapter provides knowledge of cell cycle. The main contents of this chapter include all of the following: List the phases of the cell cycle and describe the key events of each phase, describe the process of DNA replication.
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prepared by Janice Meeking, Mount Royal College
C H A P T E R
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3
Cells: The Living Units:
Part D
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Cell Cycle
until it reproduces
• Interphase
• Cell division (mitotic phase)
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Interphase
• G1 (gap 1)—vigorous growth and metabolism
• G0—gap phase in cells that permanently cease dividing
• S (synthetic)—DNA replication
• G2 (gap 2)—preparation for division
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G 1 Growth
S Growth and DNA synthesis G 2
Growth and final preparations for division
M
G 2 checkpoint
G 1 checkpoint (restriction point)
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Centrosomes (each has 2 centrioles)
Nucleolus
Interphase
Plasma membrane
Nuclear envelope
Chromatin
Interphase
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DNA Replication
nucleosomes
exposes complementary chains
replication fork
for building a new complementary strand
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DNA Replication
• Continuous leading strand is synthesized
• Discontinuous lagging strand is synthesized in segments
• DNA ligase splices together short segments of discontinuous strand
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DNA Replication
the original
replication
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Adenine
Thymine
Cytosine
Two new strands (leading and lagging) synthesized in opposite directions DNA polymerase
DNA polymerase
Lagging strand
Leading strand
Free nucleotides
Old strand acts as a template for synthesis
of new strand Chromosome
Helicase unwinds
the double helix and
exposes the bases
Old DNA
Replication fork