Mr. Johnson is giving a lesson on enzymes in his freshman biology class. Mr. Johnson displays six beakers with either a chemical substrate or chemical enzyme in them. He tells the class that each of the substrates will spontaneously breakdown (degrade) over a set period of time. He asks the class to identify what would happen if he were able to apply the correct enzyme to the correct substrate. Which of the following is the best answer to give Mr. Johnson?

During crossing-over, a. genetic material is exchanged between nonsister chromatids, resulting in new combinations of alleles. b. nonsister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. c. one homologous chromosome of a tetrad is exchanged with another tetrad, resulting in new combinations of alleles. d. sister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. e. genetic material is exchanged between sister chromatids, resulting in new combinations of alleles.