Final answer:
In a mutation that prevents the formation of cristae in mitochondria, researchers would observe inefficient colocalization of respiratory chain components and disrupted proton pumping into the intermembrane space, which are critical for ATP production. Therefore, the correct answer to this question would be i and ii.
Step-by-step explanation:
If researchers discovered a mutation in Drosophila melanogaster that prevented the formation of cristae in mitochondria, they would observe that the components of the respiratory chain would not colocalize efficiently. Mitochondrial cristae increase the surface area for the respiratory chain enzymes and complexes that are involved in electron transport and ATP synthesis. The absence of cristae would disrupt the organization and local concentration of these proteins, impairing the cell's ability to produce ATP effectively.
Another observation might be that H+ ions could not be pumped into the intermembrane space as effectively, because the electron transport chain, which drives this process, would be compromised due to the absence of cristae. The cristae are necessary for the proper function and maximum efficiency of oxidative phosphorylation.
The choice stating that NADH2 could not be transported from the cytoplasm into the mitochondria and that proteins synthesized in the cytoplasm would not be able to enter the mitochondria is incorrect as these processes are not directly dependent on the presence of cristae. Therefore, the correct answer to this question would be i and ii, indicating that the mutation affecting cristae formation would likely impact the efficiency of the respiratory chain's colocalization and the proton gradient's formation in the intermembrane space.