Mendel Figures Out Dominance

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Students will follow in Mendel's footsteps and be able to determine dominance of different traits using a virtual lab.

Big Idea

A simple test can be used to explain big ideas.


10 minutes

To start this lesson I ask students to add the post-its they generated at the close of the previous lesson to their concept maps and create the phrases that link these concepts together. I expect them to add alleles, homozygous and heterozygous, genotype and phenotype

In order for the students to be successful in today's lesson, I review the following concepts by writing the terms on the board, and having students provide me with the definitions.

  • Homozygous: Trait made up of two of the same allele (XX or xx).
  • Heterozygous: Trait made up of two different alleles (Xx).
  • Dominant trait: Trait that needs only one allele to be shown (XX or Xx)
  • Recessive trait: Trait that needs both copies of the allele to be shown (xx)
  • Phenotype: Traits that we see (brown hair, rolling tongue, freckles)
  • Genotype: Combination of alleles that code for a trait.

I invite you to read my "In their Own Words" reflection to gain insight into what students can do with this simple exercise.

Figuring Out Dominance

40 minutes

I tell the students that their job today is to use what they know to determine dominance of specific traits. In order to do this, they will navigate to the Mendel Weblab and use the Mendel Figures Out Dominance guided notes to keep track of their work. Although they will be working with a Clock Buddy on one computer, each partner is responsible for their own sheet. 

I use clock buddies for this activity to encourage students to talk with each other, examine their understanding and collaborate with each other in finding the best explanation (SP7: Engage in Argument from Evidence), as they identify cause and effect relationships (CCC) to predict the dominance of traits.

In an ideal classroom, all the students are able to complete this work without more than the knowledge they have gained so far and the instructions I have given in the sheet. However, some groups might some more guidance, so I show how to use the interactive to figure out dominance.

I make sure students understand that they need to complete their own sheet and turn it in before class is over in order to gain their points for the day (SW). Student teams that finish early can navigate to the Genetic Breeder activity and attempt to produce specific combinations of traits in 8 generations or less.

Head over to "My Way Is Not The Only Way" to see how different students tackled this activity, and what it means to my classroom community.


5 minutes

To close this lesson, I have the students write a post-it note on my reflective chart. This chart is posted at the front of the room, and gives me a quick reference into student thinking and attitudes in the classroom.