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How do people experience taste? Some people savor the flavor of beets while others grimace in disgust. What accounts for the difference? In this lesson, students will investigate the genetic basis of taste by testing their ability to taste a bitter compound (PTC) and by sampling food.
Students will be able to:
1. Informally survey students about their taste preferences. For example, ask students to raise their hand if they:
3. If appropriate for your students, point out the genetics underlying taste. For example:
4. Tell students that special proteins on the surface of taste cells in our tongue help us detect specific flavors. These proteins (which are made up of amino acids) are called taste cell receptors. Mention that students will test factors influencing their ability to taste and to perceive flavor.
5. Give each student a copy of the Picky Eaters Student Handout PDF Document and a piece of PTC paper. Have them follow the instructions on the handout and answer the questions. For step 3, help students tally class PTC responses. Draw the following chart on the board:
6. For step 5 of the handout, give each student a spoonful of baby food in a cup and a cotton swab dipped in mint oil (e.g., peppermint, spearmint, wintergreen, or eucalyptus) or a very strong breath mint. Do not reveal the identity of the food. Students should smell the mint as they taste the food. Next, they should taste the food sample while holding their nose.
7. When students have finished the taste test, reveal the identity of the food and tally the number of correct responses. Discuss difference between taste and flavor. One way to describe it might be that taste is sensed by our tongues, whereas flavor is constructed by the brain, based on stimuli from the tongue and nose.
8. Discuss the role of genetics in our sense of taste and perception of flavor. Ask:
Point out that generic difference, such as number of taste buds, play a role in flavor perception and ability to smell. Other external factors, such as temperature, can affect how we experience food.
9. Optional Extension Activities:
Ask students to design and carry out their own taste test, involving one or more of the following:
Challenge students to create tests that weigh one variable at a time, use experimental controls, and collect quantitative data.
Discuss how genes can influence our behaviors (such as food choice), and ask students whether genes determine our choices. Our susceptibility to become addicted to certain drugs, including alcohol and cigarettes, seems to have a genetic basis. Understanding our family history is important so that we are aware of our own vulnerabilities. Point out that although our genes might make us more likely to engage in certain behaviors, many factors, such as our parents, our peers, the media, and cultural norms, influence our choices.
Discuss how genetics can influence our taste perception, while taste and smell combine to create the sense of flavor. You can also use the answer key and rubric in the Teacher Notes—Picky Eaters PDF Document to assess each student's work on the handout.