As an in class activity, have your students create a life-sized punnet square. To do this, divide them into groups of 12. If you cannot evenly divide your class into groups of 12, assign the leftover students to a group and ask them to fill roles, such as group leader or secretary. For every group, you will need to create a large punnett square outline, labeling the genes on the outside of the square but leaving the inside squares blank. You can draw this on several pieces of butcher paper or take the activity outside and draw it in chalk. Also create four signs with a capital "A," four signs with a lower-case "a," three signs of an uncurled tongue and one sign of a curled tongue. Instruct each student in the group to choose a sign to hold. Next, ask all the students with gene signs to go to the appropriate square. Tell them there should be an "AA" square, an "Aa" square, an "aA" square and an "aa" square. Next, ask the students with tongue signs to go to the genotype that matches their phenotype. The curled tongue students should be in the "aa" square. Ask each group to briefly explain why they arranged themselves the way they did and how phenotype and genotype are related.
In class, ask your students to draw a punnet square for eye color. Tell them to label the genes "B" and "b." Under the genotype listed in each square, tell them to draw an eye of the appropriate color. "BB," "Bb" and "bB" will all be brown. The "bb" square will be blue. Next, have them create a family tree of eye color, starting with themselves and going back to their grandparents. For every person, they should list both the genotype and phenotype. It may help to create a chart for them to fill out. Explain to them that by referring to the punnett square, they will be able to trace their genetic history. Give an example of how a genetic history is created, using your own eye color as an example. Say, "I have blue eyes, and both of my parents have blue eyes. This means that we all have a 'bb' genotype. I talked to my parents and asked them what color eyes their parents had. My grandmother on my mother's side had brown eyes. Since my mother has blue eyes, my grandmother had to have a genotype of 'Bb.'"
For a quick activity, ask your students to create a punnett square for gender. Under each genotype, ask them to draw a stick figure of a boy or girl to indicate phenotype. Ask them to provide a brief explanation of why they themselves are male or female. For a challenging followup activity, ask your students to create a punnett square that shows the genetic combination of both gender and eye color. It may help to create a chart with the genes already listed outside of the squares. These would be "XB, Xb, XB and Xb" on the top and "XB, Xb, YB and Yb" along the side. You should have 16 blank squares. Explain to the students that in each square they should list the genotype and draw the phenotype. For example, the square in the left-hand corner would be genotype "XXBB." This means the phenotype is a female with brown eyes.
Create a worksheet with 10 to 12 punnett squares. Use the example of brown dogs, which have at least one dominant C gene, and white dogs, which have two recessive c genes. Each punnett square should present the genes of two parents. Ask your students to fill in the possible genotypes for these two dogs' offspring. Next, ask them to identify the phenotypes of the parents and each potential puppy. For example, a punnett square with two "Cs" across the top and two "Cs" along the side means that both parent dogs are brown and that all their puppies will be brown.