Making Babies with Punnett Squares
In the BabyMaker activity, students begin by identifying their own genetic traits, answering a series of questions about their facial features. As they input their phenotype, an animated cartoon representation of themselves as a baby is created. Students then randomly generate a second baby to “cross” with, and proceed to create new generations of babies by filling in Punnett Squares and by reading probabilities of expressed traits from Punnett Squares that are filled in for them. If they make a mistake, their babies might be missing a body part! This activity was heavily inspired by a paper-based activity from Cheryl Massengale.

This lesson is centered around my BabyMaker web app:

Topics addressed:
Genetics – Punnett Squares, phenotypes, genotypes, traits, genomes

Primary CT concept: algorithmic thinking. To fill out a Punnett Square is to be the “computer” performing the correct algorithm, taking the input (the alleles of each baby) and creating the output (the probability matrix for the new baby’s trait).

Students will be able to:
Complete Punnett Squares given two sets of traits
Predict the likelihood of a trait being expressed given its Punnett Square

This activity assumes your students have already been taught how to fill out and read Punnett Squares – it is a practice tool, not a teach-for-the-first-time tool.

Suggested lesson breakdown:
5min – walk through the activity end-to-end in front of your class, showing how they select their own traits and how they both fill out and read the Punnett Squares using the handout
25-40min – students work independently in BabyMaker. If students don’t finish all five generations of their baby before the end of class, they can easily submit their high score at any point, no matter how far they got. Encourage accuracy over speed!

For further information and relevant standards, please visit


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  • BabyMaker-Reference-Sheet.pdf

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Created: Jan 23, 2017

Updated: Feb 22, 2018

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Creative Commons "Sharealike"

Creative Commons "Sharealike"