| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Biology |
| Lesson Topic: interpret and construct genetic diagrams, including Punnett squares, to explain and predict the results of monohybrid crosses and dihybrid crosses that involve dominance, codominance, multiple alleles and sex linkage |
Learning Objective/s:
- Describe the different patterns of allelic interaction (complete dominance, incomplete dominance, codominance, multiple alleles, sex‑linked inheritance).
- Construct accurate monohybrid and dihybrid Punnett squares for each interaction type.
- Interpret genotype ratios from Punnett squares and convert them to phenotype ratios.
- Predict offspring outcomes for given parental genotypes, including sex‑linked crosses.
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Materials Needed:
- Projector or interactive whiteboard
- PowerPoint slides with example Punnett squares
- Student worksheets containing practice crosses
- Colored markers or pens for drawing diagrams
- Set of genotype cards for a hands‑on gamete‑matching activity
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Introduction:
Begin with a quick “What trait did your parents pass to you?” poll to activate prior knowledge of inheritance. Briefly recap genotype vs. phenotype and state that today’s success criteria are to build and read Punnett squares for a range of inheritance patterns.
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Lesson Structure:
- Do‑Now (5’): Students complete a short matching task linking terms (allele, genotype, phenotype, dominance).
- Mini‑lecture (10’): Review allelic interactions with visual examples on the screen.
- Guided Practice (15’): Whole‑class construction of a monohybrid Punnett square for complete dominance, followed by teacher questioning.
- Station Rotation (20’): Four stations – incomplete dominance, codominance, multiple alleles, sex‑linked cross. Students rotate, build squares using genotype cards, and record ratios.
- Whole‑class Dihybrid Demo (10’): Teacher models an AaBb × AaBb cross, highlighting independent assortment.
- Check for Understanding (5’): Quick‑fire quiz (Kahoot) on interpreting genotype/phenotype ratios.
- Wrap‑up Discussion (5’): Students summarise key differences between the interaction types.
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Conclusion:
Recap the steps for constructing and interpreting Punnett squares, emphasizing how each inheritance pattern alters the expected ratios. Collect an exit ticket where each student writes one real‑world example of a trait and the corresponding Punnett square outcome. Assign homework: complete the worksheet with three additional crosses, including one sex‑linked scenario.
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