Stalking the Genetic Basis of a Trait
This activity supports the film Popped Secret: The Mysterious Origin of Corn. Students analyze data on the expression of the tb1 gene to explain how variations in this gene played a role in the evolution of corn.
The activity starts with students watching the film, which describes how corn evolved through artificial selection from a central American grass called teosinte. Researcher John Doebley discovered that the differences between corn and teosinte are largely the result of variations in just a handful of genes.
In this activity, students learn that one of those genes is called teosinte branched 1, or tb1. They then analyze differences in both the coding and regulatory regions of the tb1 gene in corn and teosinte and make claims about the effects of those differences on the expression of the tb1 gene, on the TB1 protein, on the expression of other genes, and on the phenotype of the plants.
Student Learning Targets
Analyze amino acid and DNA sequences to determine that differences in the coding region of tb1 are not the cause of phenotypic differences between corn and teosinte but are evidence of a close evolutionary relationship.
Construct an explanation based on evidence for how the structure of DNA in a regulatory region determines the expression of proteins that further affect the expression of other genes.
corn, gene expression, gene regulation, Hopscotch insertion, maize, mutation, phenotype, regulatory region, tb1 gene, teosinte
Studer, Anthony, Qiong Zhao, Jeffrey Ross-Ibarra, and John Doebley. “Identification of a functional transposon insertion in the maize domestication gene tb1.” Nature Genetics 43, 11, (2011): 1160–1163. https://doi.org/10.1038/ng.942.
Studer, Anthony J., Huai Wang, and John F. Doebley. “Selection during maize domestication targeted a gene network controlling plant and inflorescence architecture.” Genetics 207, 2 (2017): 755–765. https://doi.org/10.1534/genetics.117.300071.
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HS-LS1-1, HS-LS3-1, HS-LS4-1; SEP1, SEP4, SEP6
1.A.4, 3.A.1, 3.A.4, 3.B.1, 3.C.1; SP3, SP5, SP6
3.1, 3.4, 7.2
CC1, CC3; DP1