In mid-February, Class 7 students gathered in Room 712 for a captivating lesson led by a special teacher. “Hi, everyone,” greeted Class 12 student Willa Switzer from her spot at the front of the room, the words “Fruit Flies and Genetics” illuminated on the smartboard behind her.
“I know you’ve been learning about genetics, which coincides with my Individual Study,” she began. An optional endeavor for seniors, Chapin’s Individual Study Program allows students to concentrate on and explore an area of interest deeply. Should their junior year proposal be approved, those students passionately delve into their extensive and self-directed study during the fall or winter terms the following year.
Willa, who’s in the midst of her work, has tentatively titled her study “2nd and 7th grade students solidify abstract biological concepts in their hands-on study of Drosophila.” Advised by Chapin’s Coordinator of Scientific Inquiry and Laboratory Research Elaine Pan, Willa also completed a similar, age-appropriate lesson with Class 2.
Willa began by teaching the seventh graders how to use Punnett Squares. “These help us learn about genetics and predict what offspring will look like and what traits they’ll have,” she explained. They also discussed the difference between homozygous alleles (two of the same) and heterozygous (two different alleles).
“A capital letter means that the allele is dominant and a lowercase letter indicates that the allele is recessive,” Willa said as students practiced writing out Punnett Squares.
“In Upper School, we study Drosophila, or fruit flies, to predict genotype,” the senior shared, noting that genotype is a unique sequence of DNA. (Each scholar in our US “Fly Lab” class is tasked with generating and characterizing one novel fly strain, which is achieved by crossing individual flies from specific genetic lineages.)
Willa explained that scientific researchers, including her and her US peers, can use genotypes and phenotypes (observable traits) of Drosophila offspring to determine if a gene is dominant or recessive – and that’s exactly what the seventh graders would be doing today, too!
The Class 7 scientists were tasked with determining whether the “W” gene (which codes for white eyes) is dominant or recessive. The students filled out two Punnett Squares – one assuming that the W gene is dominant (which equaled a 100% chance the offspring would have white eyes) and one assuming it is recessive (which equaled a 100% chance the offspring would have red eyes).
After gently passing out tiny test tubes filled with fruit flies and their food, Willa showed the students how to use an anesthetic chemical called “FlyNap” to put the flies to sleep before crossing them.
“It’s so important to label,” Willa explained, showing an example of an US tube. She instructed the seventh graders to add the date, their group’s initials, the number of flies and the genotypes of the mom and dad.
When Willa returned a few weeks later, the new flies had hatched! Using a tiny paint brush of sorts, students carefully moved the cotton ball cap to the side and deposited a bit of FlyNap into their test tubes. The students gently deposited the sleepy flies onto an index card and observed them under a microscope.
With a drum roll, the students discovered…red eyes! With this evidence in hand, they uncovered that the W gene is, in fact, recessive. “Using CER (Claim, Evidence and Reasoning), write out your answer to our claim and what you observed,” Willa said.
When reflecting on her teaching experience, the senior shared, “Because I worked with both Lower and Middle School students, I had the opportunity to see how live animals can be used in the classroom across all three divisions. I loved the opportunity to work with students of all different ages, and see how they were able to use Drosophila to bring what they have been studying in science class to life.”
Willa, who applied to colleges as a biochemistry major and education minor, gushed, “I love science, as well as teaching, so the opportunity to not only observe but also be able to teach classes at Chapin was an invaluable experience.”
