A rare double mutation was found to be naturally occurring in switchgrass, a grass species related to maize. The mutations lead to the overexpression of both Rubisco polypeptides and RAF . Based on the information provided, explain how the fitness of the mutant switchgrass will compare with that of a mutant switchgrass overexpressing RAF alone. The small subunits of Rubisco are encoded by a nuclear gene while the large subunits of Rubisco are encoded by a chloroplast gene. A particular maize plant has a mutation in the allele encoding the large subunit of Rubisco. Pollen from this mutant plant is used in a cross with a plant that contains the normal allele. Explain why the offspring resulting from this cross will not express this mutation.