Students look to strawberries to learn about DNA
By Mary Stadnyk | Associate Editor
“DNA” is something people hear about or learn about, but is it something that can actually be seen? The answer is yes.
That’s what eighth-graders in St. Aloysius School, Jackson, have learned during their science studies, which had them extracting and observing the DNA in strawberries.
Noting that studying the DNA of strawberries is a “well documented lab for students in middle school and high school,” Patricia Arfuso, the school’s sixth, seventh and eighth-grade science teacher, explained that during the school’s second trimester, students began studying cells, heredity and DNA in earnest. Part of their studies involved learning the procedure for making a model of DNA and how to use an extraction kit before conducting an actual lab experiment.
Explaining how the study of DNA of strawberries evolved, Arfuso said that earlier in the school year, the students had completed labs in which they used microscopes to observe their own cheek and skin cells, onion cells and bacteria cells. They have also observed osmosis in potato cells and cellular respiration in yeast cells by capturing the carbon monoxide produced by the yeast and measuring the rising temperature as the yeast consumed sugar. Students have also swabbed various areas in the science lab, inoculated petri dishes and cultured the bacteria collected on the swabs.
In studying strawberries, however, students learned that the fruit contains more DNA per cell than other fruits and even human cheek cells, Arfuso said. “Strawberries are octoploids which means that each cell has eight copies of each chromosome and that’s a lot of DNA per cell. Strawberries are also easy to mash which breaks open the cells,” she said.
In conducting their experiment, Arfuso said the students “used their knowledge of cells to understand why each substance was needed and how it worked.” Typical household items used included dishwashing detergent to dissolve the lipids of the cellular and nuclear membranes; salt to break up the proteins that bind the nucleic acids, and cold alcohol to precipitate the DNA.
Ultimately, Arfuso said, students came to understand first-hand that plants, like all living organisms, have DNA. “They were able to see this DNA with the naked eye because they extracted it from thousands of strawberry cells.
“It is one thing to learn about DNA, make a model of it, or see it in pictures; it is quite another thing to see the DNA with your own eyes and touch it with your hands,” she said.
The eighth-graders agreed when their teacher said that, “This hands-on learning is incredibly valuable.
While Shawn Tirone remarked on how the “lab really showed us what DNA looks and feels like, which is what we’ve been learning about,” classmate Ava Goble chimed how “cool” it was to watch the DNA precipitate to the top and actually touch and feel it.
Emma DiUbaldi was enlightened to “see DNA in real life and not from a textbook or Google picture,” and Gabe Anama simply stated that “This was one of the best labs I have ever done.”