WASHINGTON WATERSHEDS



Overview

Identifying observable traits is an excellent way to introduce students to genetics. They begin by tasting PTC paper for bitterness to discover who in the room can taste it and who cannot. They then compare two randomly selected students to investigate how they are alike and how they differ. They continue investigating various genetic and non-genetics traits about themselves. Three of the genetics traits are selected and displayed on a genetic tree for the entire classroom.

Time

One 50-minute period.

Purpose

Students find and recognize a series of observable genetic traits about themselves that will differ from other students.

Materials

For each group of students:

• PTC paper, 100 strips/vial (order #AP7989, Flinn Scientific, 800-452-1261)

• Hard candies

• Hand mirrors

• Scissors

• Post-it Notes, 1 1/2 X 2 “, any two different colors.

• Human Biophoto Sheets (Carolina AA-17-4831, AA-17-48232)

• Student Sheets 2.1 - 2.4

For the teacher:

• Transparencies of Student Sheets 2.1 - 2.4

• Genetic Traits Tree

• Large wall graph for PTC tasting data

Getting Ready

1. Make Genetic Traits Tree

2. Gather PTC paper, scissors, mirrors, post-its

3. Obtain Human Biophoto sheets

4. Make Genetic Traits Tree for wall

5. Copy leaf pictures on two different “leaf colored” paper

6. Duplicate Student Sheets 2.1 - 2.4

7. Prepare transparencies of Student Sheets 2.1 - 2.4

BACKGROUND INFORMATION

In the last activity we classified living and non-living objects. Throughout the rest of the unit, we will focus on genetics. We are going to specifically focus on traits and plant and animal cells as these are easily observable. Genetics is also a topic that most students are naturally curious about.

It is important to keep the focus on traits instead of genes in State Your Traits. Students start the activity by looking at various physical traits. Most of these traits are genetics traits and cannot be changed. Students also explore traits that are not inherited, such as pierced ears, hair color and traits that are partly determined by inheritance and partly by the environment such as height and weight..

Students begin this activity by tasting strips of PTC paper. Most of the students will taste a bitter taste. About 70% of people in the North American population are tasters of PTC, and this figure may be higher in children. The frequency of tasters also varies depending on race. People of African descent for example, taste PTC at higher frequencies than people of Northern European descent.

PRESENTING THE ACTIVITY

Can You Taste It? In this section, students taste strips of PTC paper. Hand out one strip of PTC paper to each student. They will taste this and describe how it tastes to them or if it even has a taste at all. Hand out the small colored post-its notes for graphing, and Student Sheet 2.1. Give all the males in the room one color post–it note and the females another color. Have them graph their ability to taste PTC paper (or not) on a classroom graph. Students complete Student Sheet 2.1 and discuss their results.

What are My Traits? Hand out Student Sheet 2.2 and mirrors. In this section, students determine what traits they have and record them on to their individual Student Sheet 2.2. After the students have had ample time to identify several traits, orchestrate a class discussion to allow students to compare their traits with classmates. As each students is unique, different students will report different traits. Elicit why students think they differ.

State Your Traits. In this section, students identify more traits. Some traits may be genetic and some are not. Hand out Student Sheet 2.3. Allow students adequate time to identify these new traits and fill out the chart on Student Sheet 2.3. Orchestrate a class discussion to allow students to share their findings. Which traits do they think can be changed and which cannot?

Genetic Traits Tree. In this section, each student records their particular combination of three traits on a large genetic traits tree hanging in the classroom. This will be shared with the others. Make a tree like the example below on the bulletin board or out of butcher paper. Hang it where it is easily accessible for the students. The Genetic tree can easily be made of other traits. Some work better than others. We have selected three (PTC taster, tongue rolling and widows peak) to start building your tree. Hand out Student Sheet 2.4 and allow time for students to fill out the information on their leaf about each of the three traits. You may continue this with other traits as you discover them or select different traits if your students choose. Students start at the trunk of the tree and answer the first questions, " can they roll their tongue or not?" This will determine which way they will proceed. They then continue up to the next branch and answer that question. They continue branching out with their traits until they have found the last branch that matches them. They hang their leaf on this branch. When the entire class has finished, orchestrate a class discussion to allow students to share where they placed their leaf and why they think everyone's leaf is not in the same area.

Who Has My Traits Game? Students play this game as a class. Have the entire class stand up. One student volunteers to share their traits. As the volunteer student shares one trait, everyone who does NOT share that trait sits down. Continue doing this until only one other student or no students are left standing. If there is one student left, you may mention that this could be the volunteers "twin" because we only considered a few traits.

Discussion Questions

1. Did any of the inherited traits surprise you? How about the non-inherited traits?

2. How many traits does it take to show how unique a person may be?

3. Why do you think scientists care about genetics?

4. Read the Interest Link on Genetic Diversity. .

Assessment Strategies

1. As a group, evaluate how you worked together in figuring out your traits. Did you participate? Focus on each activity. How could you improve your participation?

2. What if all the people in the world had the exact same traits. What could happen to genetic diversity? What are your ideas?

What Are My Traits?

Individual Data Collection Form

Sex (circle one) Male Female

Age: ______

Your Height: __________________

Circumference of your head: ___________________

|Trait |Yes |No |

|Tongue Rolling | | |

|Widow's Peak | | |

|Dimples | | |

|Earlobe Attachment |(attached) |(free) |

|Mid-digital Finger Hair | | |

|PTC Taster |(taster) |(non-taster) |

|Cleft Chin | | |

|Pierced Ears | | |

| | | |

Student Sheet 2.3

State Your Traits

TABLE

You are going to observe some traits/characteristics of each of us and record them on the chart below. Working with a partner, observe each other’s traits and fill in the chart. When you are finished fill in the other two people at your table, so you have a total of four student names.

|Students Name |Male or |Eye color |Pierced Ears |Attached Ear |Tongue Roller |Widow’s Peak |Hair length |Dimples |Hair on Middle |Hair Color |

| |Female | | |lobes | | | | |finger | |

| | | | | | | | | | | |

| | | | | | | | | | | |

| | | | | | | | | | | |

| | | | | | | | | | | |

Student Sheet 2.5

Who has my Traits Game?

This game is played with the entire class. The entire class needs to stand up. One student volunteers to share their traits. As the volunteer student shares one trait, everyone who does NOT share that trait sits down.(e.g. "I can roll my tongue".) The volunteer goes through several traits and each time the students who do Not share that trait sit down. Continue doing this until no students are left standing.

Before beginning the game answer the first question.

How many traits do you think it takes to set you apart from other students in your class (or to show how unique you are)?

Does the volunteer student and the last students left standing look alike?

What traits do they have in common?

What traits are different? Name as many as you can.

Reconsider the question asked before you played the traits game.

How many traits do you think it takes to set you apart from other students in your class (or to show how unique you are)?

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