Making Babies with Punnett Squares

Grade 7, 30-45min

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.

Making Babies with Punnett Squares

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!

Next Generation science standards:

  • NGSS.MS-LS3-2
    Develop and use a model to describe why asexual reproduction results in offspring with identical genetic information and sexual reproduction results in offspring with genetic variation.

Common Core standards:

  • CCSS.ELA-Literacy.RST.6-8.3
    Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.