Lesson Plan: Complementary Genes Biology

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to describe the effect of complementary genes on gene expression and apply this to given examples.


Students will be able to

  • recall that complementary gene action occurs when expression of a trait is controlled by two different genes,
  • recall that expression of different genes is not independent,
  • analyze Punnett squares to show the impact of complementary genes on predicted phenotypic ratios,
  • apply knowledge of complementary genes to common examples, such as flower color in pea plants.


Students should already be familiar with

  • monohybrid crosses,
  • dihybrid crosses,
  • dominant and recessive alleles.


Students will not cover

  • codominance, incomplete dominance, or multiple alleles,
  • epistasis in disease and medicine.

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