Furry Family

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Students will practice the use of Punnet Squares to determine the probability of a trait appearing in an offspring.

Big Idea

A little game play reinforces concepts.


In this lesson students continue to grow in their understanding of several Disciplinary Core Ideas:

  • LS1.A: Structure and Function – All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins.

  • LS3.A: Inheritance of Traits – Each chromosome consists of a single very long DNA molecule, and each gene on the chromosome is a particular segment of that DNA. The instructions for forming species' characteristics are carried in DNA.

  • LS3.B: Variation of Traits – In sexual reproduction, meiosis can create new genetic combinations and thus more genetic variation.

Students will engage in several Scientific Practices – (SP2) developing and using models; (SP4) analyzing and interpreting data; (SP6) constructing explanations.

As students work independently to determine the probability of several crosses, they will have an opportunity to explore the Crosscutting Concept: Patterns -"Patterns in the natural and human designed world can be observed, used to describe phenomena, and used as evidence." They will be using patterns to identify cause and effect relationships and use Punnett squares to identify patterns in data.


10 minutes

I engage the students in the lesson by displaying my slideshow "Why do I care about Punnett squares?". The slideshow explains how Punnett squares can be used to predict the probability parents passing on genetic disorders to their children.

Punnett Practice

40 minutes

I tell the students that today they will play an online game to practice creating Punnett squares and identifying specific "desirable" traits. I distribute the Furry Family Genetics worksheet and instruct the students to visit the Furry Family website from The Vital Lab (Ohio University).

I prefer that the students complete the mini-game and review questions individually. However, once they are done, I ask that they check their answers to the review questions with each other, engaging in scientific discussions with peers, as they evaluate the findings of others (SP8). I tell the students this is not about a "What did you write for # 2?", but rather about explaining their answers to each other and learning to defend their explanations (SP7). I model the conversation that I expect from them:  

"I see we disagree on the probability for the recessive in the cross between a homozygous dominant and a heterozygous. Why do you think it is 75%?"

In order to foster this type of interaction, I tell the students that as I walk the room I will be giving out patriot bucks (school-wide incentive) to students who perform this type of conversation.

Watch as a student walks through the activity and then listen to a couple of students explain what they thought about it.

Did you catch the last student's change in attitude?


5 minutes

To close the lesson, I ask the students to log on to Edmodo and post their answers to the following question:

"Dwarfism is a dominant trait. What is the probability that a heterozygous couple with dwarfism will have a child with the condition? Explain your answer using the possible genotypes of the offspring."


I like to use Edmodo for this type of quick check for understanding since it gives me the data I need to know whether to proceed with the lesson series (as in this instance) or to go back and reteach the concept.