My Science Box

This box hooks students into the study of genetics by investigating the inheritance of human traits. Drawn by students' natural curiosity about how they come to look the way they do, they learn the basics of Mendelian genetics. From this introduction, students extract DNA, build DNA models and use them to study replication, transcription and translation.

Summary
Genes and DNA are very abstract concepts for students. In order to "hook" them in, I open my genetics and evolution unit with human genetics, specifically looking at the variations in human traits. This allows students' natural curiosity about their identity to draw them into the study of heredity. There are lots of great single gene traits with simple dominance inheritance patterns to explore: earlobe attachment, tongue rolling, cleft chin, etc. There are some polygenic traits that can be explored: hair color, eye color, reach, reaction time, etc. Hair texture (curly, wavy, vs. straight) offers a good example of incomplete dominance. After collecting information from themselves and two others, the population data is collected on several large charts in order to look for and discuss the patterns.

Time
Introduction - 30 min
Collect, organize and analyze data - 50 to 100 min depending on the depth of your analysis

Grouping
Small groups in class and at home for data collection. Whole class for the analysis of the collected data.

Materials

• Copies of the "Human Traits Survey" handout
• Rulers
• Meter sticks or measuring tape
• 6-8 large sheets of butcher paper or flip chart paper, preferably with gridlines for graphing
• colored removable labeling dots

Teacher Background
If you were asked to describe yourself to a stranger so they could recognize you at the airport, what would you say? What traits make you unique and different from others? The general ways one person can different from another – height, eye color, hair color, build, complexion, etc – are called characteristics. The precise description of an individual – 5’2”, brown eyes, brown hair, fairly thin, etc. – are called the person’s traits.

Getting Ready
Day 1 - Introduction

1. Make copies of the "Human Traits Survey" handout.
2. Set out rulers, meter sticks and/or measuring tape.

Day 2 - Collect and organize data

1. Fill out the "Human Traits Survey" for yourself.
2. Create 4 large graphs on which to draw histograms of the "Traits measured in centimeters" data. Students will be placing a sticker onto the chart for each person surveyed, eventually creating a bell curve distribution for each trait. The y axis for each trait should be labeled "Number of people".
   • Hand span - Label the x axis between 1-30 cm.
   • Reaction time - Label the x axis between 1-30 cm.
   • Reach - Label the x axis between 150-280 cm in 5 cm units.
   • Broad jump - Label the x axis between 80-220 cm in 10 cm units.
3. Create a summary table on which to synthesize the population data for the "Yes or no/multiple choice traits". Students will put a tally mark beside the applicable trait for each person surveyed.
4. Cut the sheets of sticky dots into smaller sheets with 12 dots per sheet. If you are using multi-colored dots, make sure there are 3 dots of each color per sheet.
5. Write your name (or initials) on 4 dots. Plot those dots onto the histograms where your own data falls.
6. Place a tally mark beside each of your traits on the summary table.
   

Lesson Plan
Day 1 - Introduction

1. Pose the following scenario to your students: “An exchange student from England is coming to stay with your family for a month. You go to the airport to pick her up and need to describe yourself to her so that she can find you in the crowd at the airport. In 2-3 sentences, how would you describe yourself?” Solicit volunteers to describe themselves.
2. After 5 or 6 students have shared, draw attention to some of the general categories of responses. Note how some descriptors are biologically based (eye color, ethnicity, hair color, height, etc.), whereas others are environmental (clothing, accessories, dyed hair, etc.). In this class, we will focus on the biological descriptors.
3. Go over the vocabulary. “Characteristics” are the general category of descriptions (height, eye color, etc.) whereas “traits” are the precise description of an individual’s characteristics (5’2”, blue eyes, etc.).
4. Pass out the human traits survey. Read the instructions together, then answer any questions about the survey.
5. Allow students to work individually or in pairs to survey their traits.
6. Completion of the survey for individuals not in your classes should take place as homework that evening.

Assessment

1. Collect Traits Survey forms.
2. Collect lab notebooks with students’ summary tables and graphs.
3. Give students a data set for a trait like height or SAT scores and ask them to generate a histogram independently.

Going Further

1. Enter into a more serious discussion of Mendelian genetics and the allele combinations that determine various traits. See Making Babies lab for a one potential way to lead this discussion.
2. Have students to compare one population to another. Are the adults surveyed different than the kids? Ask a nearby school (or different classroom within the same school) to conduct the same survey and compare your results. Another way to investigate this type of information is through the CIESE Collaborative Project. They have compiled a very large database of population genetic information from schools around the world concerning the following traits: earlobe attachment, white forelock, dimples, hitchhikers thumb, bent pinkie, mid digit hair. Their database may be downloaded in Excel format from their website.

Sources
The idea for this activity was inspired by Katie Ward, a superwoman science teacher from Aragon High School. Another traits survey activity for the classroom with a slightly different twist can be found through the NASA Explores website.

Any resource list I might compile would be incomplete next to the genetics resource list created by 42Explore.

Summary
This is an extension of the Human Traits survey activity designed to introduce students to genes, genotypes, and simple inheritance patterns. Using information from the Human Traits Survey, students make guesses about their own genotype, create gametes from their genotypes, then make “babies” with a partner. Along the way students discover answers to the questions: What are genes? How are genes (and traits) passed on? How are gametes different than other cells in our body? Why do I look like mom in some ways and dad in other ways and neither of them in still other ways? Why don’t siblings look alike?

Time
50 minutes

Grouping
Individual initially then later in pairs. The teacher should devise a way to break the students into pairs (ramdomly or assign beforehand). Allowing students to pick their own partners is NOT a good idea for this activity. It is not necessary to have mixed gender pairs. In fact, the same gender pairs tended to be more mature about the whole thing.