At a Glance


  • STEM
  • Biology

Instructional Level

  • College & CEGEP


  • General Biology I

Tasks in Workflow

Social Plane(s)

  • Individual
  • Group

Type of Tasks

  • Collecting & seeking information
  • Discussing
  • Reading
  • Taking a quiz & test

Technical Details

Useful Technologies

  • Clicker System
  • Interactive whiteboards

Class size

  • Small (20-49)


  • Single class period (< 90 mins)

Instructional Purpose

  • Application & knowledge building
  • Assessment & knowledge refinement


This activity examines readily detectable traits in humans: the variation in the ability to taste the chemical phenylthiocarbamide (PTC) and to exhibit tongue rolling.

Using self generated data and related questions, students will explore Mendel’s principles of inheritance and variation within populations. PTC testing facilitates discussion about the phenotypic differences due to the single nucleotide polymorphisms (SNPs). Students will review Mendelian inheritance, genetic variation such as SNPs and other gene mutations and human pedigrees. Student PTC data is used for a population genetics exercise using the Hardy-Weinberg Model.

Instructional Objectives

  • Students will be able to explain the relationship between genotype and phenotype
  • Students will be able to analyze data and draw conclusions between the ability to taste the chemical phenylthiocarbamide (PTC) and tongue rolling

Workflow & Materials


Activity Workflow

View on CourseFlow

Contributor's Notes

Edward Awad

Edward Awad

Vanier College, Montreal, QC

  • The exercise involves personal and memorable example of Mendelian inheritance and the Hardy-Weinberg model;
  • PTC testing highlights how people can experience the same stimulus differently.
  • Given the nature of the activity keeping students on task and answering questions can be challenging;
  • Students sometimes falsely report results of the PTC strips (false positives).
  • Give each student one PTC and one control test strips, omit data from students who can taste both strips.

Applied Strategies


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