Using kernel color in maize to explore Mendelian genetics
--Ken Kubo and Nicholas Burger, Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721, 520-626-4664, http://biotech.biology.arizona.edu, email: kmkubo@U.Arizona.EDU

In order to promote hands-on inquiry into the concepts of Mendelian genetics, we have developed a maize genetics activity for the high school classroom. We are currently using this in Tucson, AZ classrooms. In this activity students investigate the inheritance patterns of two alleles of the b gene, which regulates the synthesis of anthocyanin pigments in maize. One of the b alleles, B-Peru, produces dark purple kernels, whereas the second allele, B', produces very little or no detectable kernel pigment. By observing kernel color through several generations in maize pedigrees, students can explore how physical characteristics are inherited.

The students examine ears from B-Peru and B' maize stocks and record their observations regarding kernel color. The students then use their observations to analyze pedigrees of B-Peru and B', in which the two maize stocks were intercrossed through controlled pollinations and resulting ears saved for analysis. In one pedigree, the B-Peru and B' maize stocks were cross-pollinated, producing ears that contain all dark purple kernels. In the next generation, plants grown from these dark kernels (F1) were crossed with the original B' parental stock. The resulting ears contain dark and light kernels in a 1:1 ratio. In another lineage, plants grown the F1 kernels were intercrossed, producing ears with dark and light kernels in a 3:1 ratio.

Working in groups, the students count the number of kernels of each color on the maize ears from the pedigrees. After determining the color frequencies on the maize ears, the students are asked to explain how these patterns (1:1 and 3:1) arise. As the students generate alternative explanations and test some of them using the pedigrees, the teacher can introduce several principles of Mendelian genetics, and the students can apply them to the pedigrees. Students learn how to integrate their understanding of genetic concepts such as genes, gametes, dominant and recessive traits, and independent assortment.

Students have responded very positively in their evaluations of this activity, especially since maize provides a visually appealing demonstration of inheritance patterns. They also appreciate how their understanding of maize genetics can be applied to the inheritance of human genetic diseases, such as cystic fibrosis and Tay-Sachs disease. 


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