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, including: different breeds of dogs, some good at hunting and retrieving game and others that are specifically bred for companionship and living in a house; and different breeds of cattle, some bred for milk production and others bred specifically for beef. Corn has been developed and is constantly being improved to produce higher yields in drought conditions, resistance to pests, and other advantageous characteristics through this process. Artificial selection is also important in that it 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 observe ears of corn from F2 plants produced by a dihybrid cross for the traits of kernel color and endosperm composition, which changes the shape of the kernel. The color blue is dominant to yellow and the starchy nonwrinkled endosperm is dominant to a sugary wrinkled endosperm. Students will hypothesize the genotypes of the parents (F1 generation). First looking at each trait independently, and then looking at the independent assortment or linkage between the two traits. These hypotheses will be used to make predictions that will be analyzed by collecting data and applying a chi-square test.
