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Snow White Apples?

RNAi and Genetically Modified Foods

By Ann T.S. Taylor

Snow White Apples?



The protagonist of this two-day flipped case study, “Maria,” has two problems. She doesn’t like it when the apple slices in her lunch turn brown, and she needs to find a project for her biology class that includes molecular biology, preferably one that incorporates plants. Students are enlisted to help Maria understand Arctic Apples™, which don’t turn brown because they have been genetically modified to suppress the expression of polyphenol oxidase via RNAi. The case also explores the health, environmental, and safety aspects of growing and eating plants that have been genetically modified to use RNAi. The case applies the central dogma of biology to the creation of genetically modified foods and RNAi and includes a discussion of whether genetically modified foods should be labeled. Several videos are included with the case, including one created by the author specifically for the case. The case is appropriate for use in an introductory level biology or survey level biochemistry course.


Date Posted




  • Describe RNAi, including necessary components.
  • Interpret a plasmid map.
  • Describe how a transgenic plant is made, including the role of species specific promoters, virulence genes and antibiotic resistance selection markers.
  • Apply issues involved in the use of GM foods to a discussion of whether GM foods should be labeled. Such issues include the non-target effects for RNAi, the role of polyphenol oxidase in plant disease resistance, and how antibiotic resistance is transferred between species.


RNAi; transgenic plants; central dogma of biology; RNA; DNA; genetically modified organisms; gene silencing; antibiotic resistance; plant disease resistance; labelling; GMO


Subject Headings

Biology (General)
Cell Biology
Environmental Science
Food Science / Technology
Genetics / Heredity
Molecular Biology


Undergraduate lower division, Undergraduate upper division






Ethics, Policy issues, Regulatory issues






N/A, Discussion, Flipped, Jig-Saw, Journal Article



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