Don

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Dont Panic
Bonus 1 due today
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DNA Replication, Mitosis, and Cancer
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Genes are the parts of DNA that contain
information.
CB 5.25
Protein
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Meiosis producing gametes
For life to exist, the information (genes) must
be passed on.
Mitosis producing more cells
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Mitosis
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The Cell Cycle
DNA Replication
CB 12.4
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Complementary base pairs suggest how DNA
replication may occur
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DNA replication each strand serves as a template
for making a complementary copy
O.R.
Origin of Replication
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DNA replication each strand serves as a template
for making a complementary copy
O.R.
helicase
helicase
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DNA replication each strand serves as a template
for making a complementary copy
helicase
helicase
The two strands of DNA are unwound.
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DNA replication each strand serves as a template
for making a complementary copy
helicase
helicase
The DNA is copied.
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DNA replication each strand serves as a template
for making a complementary copy
helicase
helicase
More unwinding, more copying
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DNA replication each strand serves as a template
for making a complementary copy
helicase
helicase
The DNA has now been copied. There are now two
double-stranded DNAs
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Most DNA has multiple origins of replication
CB 16.10
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DNA replication each strand serves as a template
for producing a complementary copy
CB 5.27
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Sometimes errors are made.
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Error
Luckily, errors can be repaired.
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DNA Repair
mismatch removed by enzymes
DNA replaced
repair complete
damage or replication error
CB 16.17
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Not all errors get repaired. These are mutations.
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Errors are made during DNA replication
3,000,000,000 (3 billion) base pairs/human
cell with 1 error/1 billion base pairs not
repaired (average) 6 errors each time DNA is
replicated
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Mutations
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Cancer Cell Division Gone Wrong
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Cell division is regulated by bothpositive and
negative signals.Positive signals start the
processof cell division.Negative signals
inhibit cell division.
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CB 12.13
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Normal Mammalian Cells Have Contact Inhibition
CB 12.16
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Cancer Cells Do Not Have Contact Inhibition
CB 12.16
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Cancer

• is the loss of control over cell division.
• Tumors are normal cells that are
• dividing inappropriately.
• They stop performing their normal function, and
  are dividing repeatedly.

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Tumors in a Liver
normal
tumors
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Normal Cells
Cancer Cells
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A cell becomes cancerous when there are incorrect
positive AND negative signals.
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GO!
STOP!
cancer
CB 19.13
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Multiple mutations are required for a single cell
to become cancerous.
CB 19.14
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Benign versus Malignant cancer
CB 12.17
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How do these incorrect signals arise?
Multiple mutations are required for a single cell
to become cancerous.
CB 19.14
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Mutations
CB 17.22
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Dont Panic
Bonus 1 due today