## Replication Overview

Part 1 of 7 — Replication Overview

1. Semiconservative replication: each new DNA has one old + one new strand
2. Meselson-Stahl experiment proved semiconservative model
3. Occurs during S phase of cell cycle
4. Bidirectional from origins of replication

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### Key Details

• Semiconservative replication: each new DNA has one old + one new strand
• Meselson-Stahl experiment proved semiconservative model
• Occurs during S phase of cell cycle
• Bidirectional from origins of replication

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## Enzymes of Replication

Part 2 of 7 — Enzymes of Replication

1. Helicase: unwinds double helix
2. Primase: synthesizes RNA primer
3. DNA polymerase III: adds nucleotides 5'→3'
4. Ligase: seals gaps between Okazaki fragments

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### Key Details

• Helicase: unwinds double helix
• Primase: synthesizes RNA primer
• DNA polymerase III: adds nucleotides 5'→3'
• Ligase: seals gaps between Okazaki fragments

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## Leading & Lagging Strands

Part 3 of 7 — Leading & Lagging Strands

1. Leading strand: continuous synthesis toward replication fork
2. Lagging strand: discontinuous synthesis away from fork (Okazaki fragments)
3. Both strands synthesized 5'→3'
4. Primase must lay down primer for each Okazaki fragment

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### Key Details

• Leading strand: continuous synthesis toward replication fork
• Lagging strand: discontinuous synthesis away from fork (Okazaki fragments)
• Both strands synthesized 5'→3'
• Primase must lay down primer for each Okazaki fragment

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## Proofreading & Repair

Part 4 of 7 — Proofreading & Repair

1. DNA polymerase has 3'→5' exonuclease (proofreading) activity
2. Mismatch repair: corrects base-pairing errors
3. Nucleotide excision repair: fixes UV damage (thymine dimers)
4. Error rate: ~1 per 10⁹ nucleotides after all repair

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### Key Details

• DNA polymerase has 3'→5' exonuclease (proofreading) activity
• Mismatch repair: corrects base-pairing errors
• Nucleotide excision repair: fixes UV damage (thymine dimers)
• Error rate: ~1 per 10⁹ nucleotides after all repair

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## Telomeres & Telomerase

Part 5 of 7 — Telomeres & Telomerase

1. Telomeres: repetitive sequences at chromosome ends (TTAGGG)
2. Shorten with each replication (end replication problem)
3. Telomerase: enzyme that extends telomeres
4. Active in stem cells and cancer cells; inactive in most somatic cells

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### Key Details

• Telomeres: repetitive sequences at chromosome ends (TTAGGG)
• Shorten with each replication (end replication problem)
• Telomerase: enzyme that extends telomeres
• Active in stem cells and cancer cells; inactive in most somatic cells

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## DNA Replication: Problem-Solving Workshop

Part 6 of 7 — Problem-Solving

1. Identifying replication enzymes and their functions
2. Predicting effects of enzyme mutations
3. Diagramming the replication fork
4. Connecting replication errors to mutations

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### Key Details

• Identifying replication enzymes and their functions
• Predicting effects of enzyme mutations
• Diagramming the replication fork
• Connecting replication errors to mutations

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## DNA Replication: Synthesis & AP Review

Part 7 of 7 — Synthesis & AP Review

1. Replication accuracy and mutation rates
2. Connection to cell cycle checkpoints
3. Telomeres and aging/cancer
4. AP exam: enzyme identification and function

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### Key Details

• Replication accuracy and mutation rates
• Connection to cell cycle checkpoints
• Telomeres and aging/cancer
• AP exam: enzyme identification and function

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