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One form of genetic modification that has been used for centuries is artificial selection, or selective breeding. This is the selection of individuals or populations possessing desirable traits to produce the next generation. This process has given rise to many of the plants and animals we encounter every day. An example of this is breeds of dog, where some are good at hunting and retrieving and some are bred for companionship within a home. Another example are breeds of cattle, where some are bred for milk production and others, for beef. A third example is corn, a crop that has been developed over the years and is currently being improved to produce higher yields in drought conditions, resistance to pests, and other advantageous characteristics through this process. Artificial selection also played an important role in the development of the theory of natural selection. An understanding of Mendelian inheritance and statistical analysis of the results of crosses is important in determining the genes of an organism and the ability to produce offspring with the desired traits.
In this lab, students will:
First, students will look at each trait independently. Then, they will investigate the independent assortment or linkage between the two traits in order to make predictions that will be analyzed by collecting data and applying a chi-square test.
Students who demonstrate understanding can:
Students should be cautioned to be careful when handling ears of corn. If handled with care, ears may last many years, but may be damaged if handled roughly. Kernels may occasionally fall off of the ears, but may be glued back into place.
Length of Time for Preparation: 15 minutes
Length of Time for Classroom Teaching: 1.5-2 hours
A chi-square test is used to evaluate the proposed genotypes of the parent generation that produced the observable offspring. The proposed genotype is the hypothesis. Probability is used to predict the number of individuals with different traits that would be expected in the next generation if the hypothesis is correct. The equation for performing a chi-square test is shown in Figure 1.
When only two phenotypes are possible, there is only one degree of freedom. With the agreed upon probability of a Type I error of 0.05, or 5%, the critical value for simple, monohybrid traits is 3.841.
Introduce the topic and assess students for prior understanding.
Let students discuss their ideas and guide the discussion without telling them if they are right or wrong.
Guided Introduction Monohybrid (Kernel Color)
Smooth vs. Round
A lab group received an F2 ear of corn that appeared to have equal numbers of blue and yellow kernels.
1. What F1 genotypes would most likely produce this ear of corn?
2. If this hypothesis is correct, how many kernels out of 100 should be blue? How many should be yellow? ½ x 100 = 50 blue and ½ x 100 = 50 yellow
3. If the kernels were counted and 44 were yellow and 56 were blue, conduct a chi-square test on your hypothesis.
Critical value for 1 degree of freedom, and Type 1 error probability = 3.841, so we fail to reject the hypothesis.
To learn more about agriculture careers, visit https://agexplorer.ffa.org/.
Any educator electing to perform demonstrations is expected to follow NSTA Minimum Safety Practices and Regulations for Demonstrations, Experiments, and Workshops, which are available at https://static.nsta.org/pdfs/MinimumSafetyPracticesAndRegulations.pdf, as well as all school policies and rules and all state and federal laws, regulations, codes and professional standards. Educators are responsible for abiding appropriate legal standards and better professional practices under a duty of care to make laboratories and demonstrations in and out of the classroom as safe as possible. If in doubt, do not perform the demonstrations.
Investing in Kansas teachers and students is a priority for the Kansas Corn Commission. We are committed to providing materials and training to support STEM education while fostering an understanding of how corn farming and agriculture fit into our daily lives. Professional development workshops are offered to teachers seeking to expand their knowledge and inquiry-based teaching skills. Workshop participants receive free lab supplies needed for the lessons.
This lesson is the work product of the Kansas Corn Commission. Our lessons are written in collaboration with Kansas teachers for use in the classroom. Teachers may copy and share this curriculum. Use of this product for commercial or promotional use is prohibited without express permission of Kansas Corn.
As the need to produce more food with less resources grows, it is important that future generations have a better understanding of agriculture and how corn farming and agriculture fit into our daily lives. That’s why the Kansas Corn STEM program provides lessons to teach science through the lens of corn. We are committed to providing free materials and training to support educators.
