The Case of the Reappearing Trait

Purple vs Green Fast Plants

Teaching: Reproduction, Genetics, Heredity with Brassica rapa

This is our version of an activity called “Who’s the Father” created by the Wisconsin Fast Plant Program at the University of Wisconsin - Madison. Their materials can be accessed through the Wisconsin Fast Plants lessons archive.

Overview and Rationale:

Brassica rapa (“fast plants”) have been developed through many years of selective breeding to be an ideal plant for study in the classroom. They have a life cycle of 35 to 40 days (seed to seed) and can grow under continuous fluorescent lights. This unit involves using fast plants as a tool for teaching reproduction, genetics, and heredity to middle school students. Students will grow plants from seed. (Students will not know that the seeds they plant (the F1 generation) are heterozygous for a specific trait-- stem color.) They will watch the plants grow and reach adulthood. They will pollinate (and dissect the flowers.) They will see seed pods develop and dry out. They will harvest the seeds (the F2 generation). They will plant these new seeds. Once these new seeds germinate into week-old seedlings, students will count the purple vs. green-stemmed seedlings. Finally, students will use their data (75% purple 25% green) to determine that the F1 generation must have been heterozygous and that the parents of each F1 seed consisted of one homozygous green parent and one homozygous purple parent.

Here is an overview of the unit including how to use the documents below.