The picture shows a completed Punnett square using an APH Graphic Aid.
Activity

Punnett Square Tactile Graphic Aid

This hands-on science activity is a tactile Punnett square utilizing an APH Tactile Graphic Aid for students who are blind or visually impaired.

Punnett squares are commonly used in the study of genetics to predict the outcomes of a genetic cross when considering one or two characteristics.  For students with visual impairment, particularly for those who are blind, Punnett squares can be very difficult. This tactile aid should effectively increase the student’s understanding of Punnett squares and his ability to complete them.

Materials

Note: Pins may be obtained from any office supply store.

Preparation

  1. Prepare an APH Graphic Aid by building the axes with either yarn or rubber bands.  The pictures shows yarn but rubber bands may be a better choice.  The yarn or rubber bands will be held by flat push pins on the top and bottom of the graphing aid in the middle and on the left and right in the middle. (See picture.)
  2. In order to give the student a clear tactile space to indicate the alleles of each parent, use flat push pins to secure a flat spring wire (from APH graphic Aid )  horizontally 1.5″ below the top of the graph board and another flat spring wire vertically 1.5″ to the right of the left side of the graph board (See picture.)
  3. Choose 2 clearly distinct types of pins for the student to use as dominant and recessive alleles.  The picture indicates white tacks as dominant and spherical blue pins as recessive.
APH tactile graphic aid
APH Graphic Aid for Mathematics

Procedure

As students are learning to complete Punnett squares, braille students who are struggling to complete them will benefit from this tactile aid. The following detailed description of the picture will precede the procedure. 

The pins used in this picture are white flathead push pins to represent the dominant allele and round head pins to represent the recessive allele.  The picture shows the cross between a homozygous dominant (2 dominant alleles) and a heterozygous individual (one dominant and one recessive allele).  When discussing seed shape (round or wrinkled) this would be written as RR X Rr.

  1. Describe the location of the alleles from the first parent as above the horizontally placed flat spring wire – one allele should be placed above each of the top 2 quadrants of the graph board in the center . Have the student place the alleles for the first parent in this position.
  2. Describe the location of the alleles from the second parent as to the left of the vertically positioned flat spring wire.  Have the students place the alleles in this position. (See picture.)

3. Assist the student to perform a cross by explaining that each square (quadrant of the graph board) will be filled by combining the allele from the top with the allele from the side.  This may require some practice. 

4. After the cross is complete, have the student describe the offspring in each box.  Ask appropriate questions about the probability of homozygous dominant, homozygous recessive, and heterozygous offspring.

5.  After the student feels confident, allow him/her to perform numerous crosses independently.

Demonstration videos for Punnett Square Tactile Graphic Aid

A student from TSBVI explains how to use the Punnett Square Tactile Graphic Aid in the videos below.  

Variations

NGSS Standards:

Middle School: Growth, Development and Reproduction of Organisms 

LS3.A: Inheritance of Traits

LS3.B: Variation of Traits:

This activity was created by Marcus Coldwell and Devin Gutierrez. 

Pictures by Ditmar Hospitál

By Laura Hospitál

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