punnet square sample
Activity

Punnett Squares

This activity provides students with a hands-on exercise that relies on shapes rather than the ability to read letters in the study of genetics.

By Sandra Craig

This activity provides students with a hands-on exercise that relies on shapes rather than the ability to read letters.  Color-coordination of foam pieces helps students who have color vision track what pieces go together, as well as allowing the instructor the opportunity to quickly assess student work.

Objectives

  1. Students will construct and analyze Punnett squares for monohybrid genetic crosses of given scenarios.  
  2. Students will analyze the expected genotypes and phenotypes that result from each cross.

Materials

Preparation

(Don’t worry about having a large number of unused pieces.  The next time you do this activity, rotate the color pairs: eyes: yellow-purple; hair: orange-green; and height: pink-blue.  Save other shapes for future tactile graphic projects, or share with another teacher. Also save the left-over plastic eggs for another activity such as the “Scientific Method”)

Prepare the worksheet:  

Print the worksheet on card stock or other heavy paper (braille paper) in order to support the foam pieces.  For braille reading students, emboss the sheets using a braille writer and tracing wheel.  

Prepare the muffin tins:  

Put the remaining (there should be 4 of each) sorted shapes in individual cups of the muffin tin.  Put the pink circles on one side of the muffin tin, and on the blue circles on the other.  Have the large circles to the left of the small circles.  When the students have completed the first Punnett Square for determining eye color, put the remaining circles back in their zip-lock bags and put the shapes for hair color in the muffin tins.  Repeat this process for when they have completed the second Punnett Square and are ready for the ‘height’ Punnett Square. 

Procedure

  1. Have a brief discussion with the class about heredity – how we inherit one-half of our traits from our mother and one-half from our father.  
  2. Explain the purpose of the Punnett Square is to predict possible outcomes if the parents possess particular alleles.  Tell the students that a large foam piece represents a dominant allele and a small one represents a recessive allele.   Most students understand dominant and recessive, but if there seems to be doubt, ask students to explain the difference between the two.  
  3. Student selects a ‘mother’ egg from the basket for eye color and places the foam pieces in the appropriate spots in the Punnett Square.  
  4. Use the proper vocabulary when the occasion arises.  For example: Describe that the mother is heterozygous (or homozygous dominant or homozygous recessive) and explain why.  
  5. Pass the worksheet around so everyone has a chance to examine it.
  6. Repeat the process for the ‘father’, select an egg, place the foam pieces, discuss his traits, and pass the worksheet around for students to examine.
  7. Stop and discuss the difference between genotype and phenotype.  What color are the mother’s eyes?  Brown Because… she’s heterozygous or homozygous dominant.  Or maybe Blue because… she’s homozygous recessive.  Ask the same questions about the father.
  8. Have students select the appropriate shapes (based on mother’s and father’s alleles) from the muffin tin and place the shapes in the Punnett square for the first offspring.  Pass the worksheet around for students to examine. Remind them that if there is a dominant trait, it should be place first. Ask students to describe the genotype and phenotype of offspring 1.
  9. Repeat the process for the remaining 3 offspring.
  10. If it appears that students understand the concept of the Punnett Square after completing the ‘Eye’ Punnett Square, hand out the ‘Hair Color’ worksheet, set up the muffin tins for that project, and allow them to beginning selecting the plastic eggs for mother’s and father’s alleles. If it seems they are still unclear, repeat the process for the hair color Punnett Square.  
  11. Intervene as needed.
  12. Check completed work and suggest corrections.  
  13. Hand out Punnett Squares Questions assignment.
eye color punnett square
Click to download the Eye Color Punnett Square
eye color punnett square
Click to download the Hair Color Punnett Square
eye color punnett square
Height Punnett Squares
pungent square questions
Click to download the Punnett Square questions.

Variations

NGSS Standards

MS-LS3-2: Heredity: Inheritance and Variation of Traits
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.

LS3.B: Variation of Traits

In sexually reproducing organisms, each parent contributes half of the genes acquired (at random) by the offspring. Individuals have two of each chromosome and hence two alleles of each gene, one acquired from each parent. These versions may be identical or may differ from each other.

By Sandra Craig

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Punnett Squares collage
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