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DNA Replication, Mitosis, and Cancer

Genes are the parts of DNA that contain information. CB 5.25 Protein

For life to exist, the information (genes) must be passed on. {Meiosis: producing gametes} For life to exist, the information (genes) must be passed on. {Mitosis: producing more cells}

Mitosis

The Cell Cycle [DNA Replication] CB 12.4

Complementary base pairs suggest how DNA replication may occur

DNA replication: each strand serves as a template for making a complementary copy Origin of Replication

DNA replication: each strand serves as a template for making a complementary copy helicase O.R. helicase

DNA replication: each strand serves as a template for making a complementary copy helicase helicase The two strands of DNA are unwound.

DNA replication: each strand serves as a template for making a complementary copy helicase helicase The DNA is copied.

DNA replication: each strand serves as a template for making a complementary copy helicase helicase More unwinding, more copying

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

Most DNA has multiple origins of replication CB 16.10

each strand serves as a template for producing a complementary copy DNA replication: each strand serves as a template for producing a complementary copy CB 5.27

Sometimes errors are made.

Error Luckily, errors can be repaired.

DNA Repair mismatch removed by enzymes DNA replaced repair complete damage or replication error CB 16.17

Not all errors get repaired. These are mutations.

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

Mutations

Cancer: Cell Division Gone Wrong

Cell division is regulated by both positive and negative signals Cell division is regulated by both positive and negative signals. Positive signals start the process of cell division. Negative signals inhibit cell division.

CB 12.13

Normal Mammalian Cells Have Contact Inhibition CB 12.16

Cancer Cells Do Not Have Contact Inhibition CB 12.16

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.

Tumors in a Liver normal tumors

Normal Cells Cancer Cells

A cell becomes cancerous when there are incorrect positive AND negative signals.

GO! STOP! cancer CB 19.13

Multiple mutations are required for a single cell to become cancerous. CB 19.14

Benign versus Malignant cancer CB 12.17

How do these incorrect signals arise? Multiple mutations are required for a single cell to become cancerous. CB 19.14

Mutations CB 17.22

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