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Di-Hybrid Crosses.

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  • Additional HL/
  • HL Genetics Activities for Learning/
  • Di-Hybrid Crosses.

This lesson gives students a guided tour of dihybrid genetic crosses using Punnett squares predicting the combination of alleles from two unlinked genes at the same time. The method described provides a good foundation for the more complex examples which come later. A quick animated introduction is followed by some di-hybrid genetics problems. An extension task for faster students provides a selection of dihybrid problems to concludes this activity.

Lesson Description

Guiding Questions

Will two different genetic characteristics always be inherited separately?

Which of the traits in the image might not be inherited separately?

Activity 1 Perform a Di-hybrid cross

Work through this Worked example of a di-hybrid cross - online animation. It explains how to calculate and predict genotypes with two genes at a time.

Activity 2: Di-hybrid Crosses - a few questions

Read the instructions about completing punnet squares for di-hybrid genetics problems and then answer the introductory questions on the Dihybrid Crosses Student Worksheet

Activity 3: More practice

Choose an extension activity from list below.

  • Use this online Punnett square calculator to work out inheritance patterns. 
    Change the genotypes of each trait in the calculator using the three suggestions in the image.
    See the Punnett square instantly.  Make a collection of screenshots.  Write a statement next to each image.

Teachers notes

Activity 1 shows students, step by step, how to do punnet squares for two genes at the same time for the dihybrid crosses.

Activity 2 has a worked example which is followed by some problems for students to solve themselves.

There are also Dihybrid questions model answers (improved) for the questions in activity 2

Activity 3 includes a collection of activities to further test student skills.