Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Biology
Lesson Topic: describe the structure of a DNA molecule as a double helix, including: the importance of complementary base pairing between the 5′ to 3′ strand and the 3′ to 5′ strand (antiparallel strands), differences in hydrogen bonding between C–G and A–T base p
Learning Objective/s:
  • Describe the antiparallel orientation of DNA strands and the 5′→3′/3′→5′ directionality.
  • Explain complementary base‑pairing rules and differentiate hydrogen bonding in A‑T versus C‑G pairs.
  • Illustrate how phosphodiester bonds form the DNA backbone and relate this to molecular stability.
Materials Needed:
  • Projector or interactive whiteboard
  • PowerPoint slides with DNA double‑helix diagram
  • Printed worksheet with base‑pairing and hydrogen‑bond tables
  • Molecular model kits (DNA strand pieces)
  • Exit‑ticket cards
 Introduction:
Begin with a quick animation of a twisting ladder to capture interest. Ask students what they know about the directionality of DNA strands and how bases pair. Outline that by the end of the lesson they will be able to describe the double‑helix structure, explain antiparallel orientation, and compare A‑T and C‑G hydrogen bonding.
Lesson Structure:
  1. Do‑now (5') – students label 5′ and 3′ ends on a blank DNA strand diagram.
  2. Mini‑lecture (10') – present double helix features, antiparallel strands, and phosphodiester bonds using slides.
  3. Guided practice (10') – work in pairs with model kits to build antiparallel strands and demonstrate base pairing.
  4. Interactive quiz (5') – click‑questions on hydrogen‑bond counts for A‑T and C‑G.
  5. Worksheet activity (10') – complete a table comparing stability and melting‑temperature implications.
  6. Recap discussion (5') – students summarise key points aloud.
  7. Exit ticket (5') – write one sentence describing why antiparallel orientation is essential.
Conclusion:
Review the main concepts: antiparallel strands, complementary base pairing, and differing hydrogen bonds. Prompt a few students to share their exit‑ticket answers for immediate feedback. Assign homework to read a short article on DNA replication and prepare questions for the next class.