Probability in Genetics Activities

Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

Learning about genetics is fun, but it also can be confusing. This series of activities helps students understand the role of probability in genetics through hands-on mini-lessons that can be used in sequential order or as standalone lessons.

Probability in Genetics

Genetics, or the study of how traits are inherited, is a difficult subject for students, and this often stems from a lack of understanding of probability. This series of fun, interactive activities can be used in order (from rock-paper- scissors to Punnett squares) to help students navigate this challenging topic.


Before delving into the probability of genetics, it's worth taking a moment to introduce students to the term 'probability' through a game of rock-paper-scissors. Before the activity, familiarize students with the rules of the game, which can be found online. After the activity, students should be ready to determine the probability using a Punnett square.


  • Copies of the rock-paper-scissors table
  • Pencils

Activity Instructions

1. Prior to the start of the activity, hand print or keyboard and make copies of a rock-paper-scissors table with two columns and 20 rows. Title the first column 'Round' and the second column 'Winner', as shown in Step 3.

2. Pose the following question: Is there a strategy to winning rock-paper-scissors?

3. Pair students and have them play the game 20 times with their partners. After each round, students should enter the winner in the table.

Round Winner
1 Rock
2 Scissors
3 Rock
4 Paper

4. Have students look over their data. Did rock, paper or scissors win most often? Or did each one win approximately the same number of times?

5. Reconvene the class and show students the probability of Player 1 winning each round.

6. Make a tree diagram to show the possible outcomes for each player in the game for rock, paper and then scissors.

Tree diagram for rock-paper-scissors

7. Have students total the number of possible outcomes and the number of ways Player 1 could have won.

8. Show students how to calculate the probability that Player 1 would win using this formula:

Number of times Player 1 wins / total number of outcomes

The answer should be 1/3.

9. Have students calculate the probability of Player 2 winning and of a tie.

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