Brief Description:

Students flip coins to determine the genetic makeup of a baby smiley from mom and dad smilies. Next, the children “breed” their smilies to try and make a specific smiley.

Grades: 3, 4, 5, 6, 7, 8

Time: 1 hour

Keywords: genetics, dominant allele, recessive allele, traits, genotype, phenotype, heterogeneous, homogenous

Lesson Objectives

  • Students will be introduced to the idea of genetics and genetic engineering
  • Students will understand dominant and recessive traits and the results of homogenous and heterogeneous genotypes.


  • Smiley Traits Key
  • Each pair of students should have:
    • 2 coins
    • 1 Smiley Genetics Worksheet


  1. Introduce Genetics and genetics-related vocabulary. Genetics is the study of heredity and the variation of inherited characteristics. What are some other inherited traits?
  2. Genes are inherited through our DNA, which we get from our parents. We get one copy of DNA from our moms and one copy of DNA from our dads. The different types of traits on the DNA are called traits or alleles. The allele on your copy of mom’s chromosome can be the same or different from the allele on your copy of dad’s chromosome. Which trait is actually expressed (the phenotype) depends on which trait is dominant. Ask all brunettes to raise their hands. Ask all blonds to raise their hands. Why are there more brunettes? Brown hair is a dominant trait!
    1. A dominant trait is inherited no matter what gene it’s paired with. A dominant allele will be expressed whether or not there are 1 or 2 copies of the allele.
    2. Have students see who has dominant and recessive traits.
      1. widows peak (dominant)
      2. hitchhikers thumb (recessive)
      3. rolling tongue (dominant)
      4. attached/detached earlobes (detached – dominant)
  3. You inherit traits from your parents.  Which gene you inherit from each parent is just like a flip of a coin, it’s completely random!
    1. Genetic engineering is manipulating this process so we can breed organisms with favorable traits. This includes seedless fruit, large vegetables, and fast horses.   
  4. Students should then do the Genetics with a Smile Worksheet (attached in Resources)
    1. Obtain two coins from your teacher. Mark one coin with a “F” and the other with a “M” to represent each of the parents. The parents are heterozygous for all the Smiley Face traits.
    2. Flip the coins for parent for each trait. If the coin lands with heads up, it represents a dominant allele. A coin that lands tails up indicates a recessive allele. Record the result for each person by circling the correct letter. Use the results and the Smiley Face Traits page to determine the genotype and phenotype for each trait.
    3. Students should then use the Smiley Face Traits chart and your results from Part B to create a sketch of their smiley face.

Extensions and Modifications:


  • Breed a Smiley


      • Students should draw a smiley using their favorite traits.
      • They should then write out the genotype for that smiley.
      • After completing its genotype, students should go around the room flipping coins with other smilies to try and ‘breed’ their smiley with others.


  • Selectively Breeding a Smiley


    • Students should draw a smiley using their favorite traits.
    • Give each student a smiley from the Full Powerpoint of Smiley Traits and Examples (attached in examples)
    • Have students breed their smiley with other smileys to try and get their favorite smiley
    • Have students keep track of how many generations it took to get their favorite smiley
    • This is an example of selective breeding. Students will only breed/mate their smiley with those that will give them offspring with desired traits.



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