| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Biology |
| Lesson Topic: describe the semi-conservative replication of DNA during the S phase of the cell cycle, including: the roles of DNA polymerase and DNA ligase (knowledge of other enzymes in DNA replication in cells and different types of DNA polymerase is not expecte |
Learning Objective/s:
- Describe the semi‑conservative mechanism of DNA replication during the S phase.
- Explain how DNA polymerase synthesises the leading and lagging strands in the 5′→3′ direction.
- Illustrate the function of DNA ligase in joining Okazaki fragments on the lagging strand.
- Compare continuous synthesis on the leading strand with discontinuous synthesis on the lagging strand.
- Interpret a replication‑fork diagram and label key enzymes and intermediates.
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Materials Needed:
- Projector and slide deck showing the replication fork.
- Printed handout with a labelled diagram of DNA replication.
- Worksheet with comparison table for leading vs. lagging strand.
- DNA model kits (or pipe cleaners) for a hands‑on activity.
- Whiteboard and markers.
- Exit‑ticket slips.
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Introduction:
Begin with a short video clip that highlights why accurate DNA copying is vital for cell division. Ask students to recall the base‑pairing rules they learned last week. Explain that today they will uncover how the cell copies its genome and how two key enzymes—DNA polymerase and DNA ligase—make this possible. Success will be measured by their ability to diagram the replication fork and describe each enzyme’s role.
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Lesson Structure:
- Do‑Now (5'): Quick 3‑question quiz on base pairing and the concept of semi‑conservative replication.
- Mini‑lecture with slides (10'): Overview of the replication fork, directionality, and enzyme functions.
- Interactive model activity (15'): Students build a replication fork using DNA model kits, identifying leading and lagging strands.
- Guided worksheet (10'): Complete a table comparing continuous vs. discontinuous synthesis and label where DNA ligase acts.
- Think‑Pair‑Share (5'): Explain in their own words why DNA ligase is essential for the lagging strand.
- Formative check (Exit ticket, 5'): Write one sentence summarising the role of DNA polymerase and one sentence for DNA ligase.
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Conclusion:
Summarise the key steps of semi‑conservative replication, emphasizing the continuous leading‑strand synthesis and the need for ligase on the lagging strand. Collect exit tickets to gauge understanding, and assign homework: students must draw a fully labelled replication fork diagram and annotate each enzyme’s action.
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