My Science Box

Getting Ready

1. Make copies of the “Making Babies” handout.
2. Set out pennies and colored pencils.

Teacher Background
One of the greatest mysteries – how we inherit traits from our parents – was solved in the 1800s by the Austrian monk Gregor Mendel. Although he published his work in 1866, it went almost entirely unrecognized until the 1900s, long after his death.

Mendel worked with pea plants, carefully characterizing their traits and cross-breeding them over many generations. He observed that many traits occur in only two different forms (short or long stems, purple or white flowers, round or wrinkled seeds). When a short plant is crossed with a tall plant, the offspring are all either tall or short, not of middle stem length. This observation countered the “blending theory” that was generally accepted at the time.

Mendels peasHe established many pure-breeding lines – for instance short plants that when cross-bred always had short offspring and tall plants that always had tall offspring. Interestingly, when a pure-bred short plant is crossed with a pure-bred tall plant, the first offspring (f1 generation) are all tall! If these tall f1 plants are cross-bred to one another, the next generation (f2) consistently have a 3:1 ratio of tall to short plants.

With these ratios and careful breeding experiments, Mendel discovered the basic laws of inheritance. He came to several conclusions:

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.

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 ...

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.

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.

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.

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.
   

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.

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