ABO Blood Groups & Codominance – Genetics PowerPoint Lesson

This clear, structured PowerPoint lesson introduces students to codominance and multiple alleles using the familiar and real-world example of human ABO blood groups.

The lesson explains how blood types are inherited, why A and B alleles are codominant, and how the O allele is recessive. Concepts are taught step by step, moving from discussion and explanation to guided practice with genotypes and Punnett squares.

Frequent Think-Pair-Share prompts, true/false checks, and worked examples help students test their understanding and address common misconceptions about dominance and codominance.

Learning Objectives

Understand how ABO blood groups are inherited

Explain codominance and multiple alleles

Use correct blood type genotype notation (Iᴬ, Iᴮ, i)

Complete Punnett squares for codominant traits

Interpret genotype and phenotype ratios

Explain why blood type compatibility matters

What’s Included

Editable PowerPoint lesson

Explanation of dominance vs codominance

Overview of ABO blood groups (A, B, AB, O)

Clear explanation of multiple alleles

Think-Pair-Share discussion questions

True/false concept checks

Genotype identification activities

Fully modelled codominant Punnett squares

Real-world blood type inheritance scenarios

Exit ticket for formative assessment

Suitable For

KS3 Science

KS4 / GCSE Biology (Inheritance & Variation)

Secondary genetics lessons

Whole-class teaching or revision

Format

PowerPoint (editable)

Notes for TES Buyers

This resource is designed for direct classroom use and works well after introducing simple dominant and recessive inheritance, as a first lesson on codominance and multiple alleles.