Refer to the table below showing observations from experiments conducted on three types of pea plants.One type of pea plant contained a mutation in the gene encoding thioredoxin that resulted in zero production of the protein thioredoxin.Another type contained two mutations: the same thioredoxin mutation as in the previous type and a mutation in the gene encoding the Calvin cycle enzyme phosphoribulokinase (PRK) that did not affect its expression.The third type contained no mutations in either gene and was designated as "wild type." Before the experiments, all plants were kept on a 14-hour light/10-hour dark cycle for several weeks. In conducting the experiments, researchers excised leaves either toward the end of a light cycle or toward the end of a dark cycle.Chloroplasts were then isolated and lysed to release the contents of the stroma, and PRK was assayed to determine its catalytic activity.Which statement about thioredoxin is consistent with these data?

Question

Refer to the table below showing observations from experiments conducted on three types of pea plants.One type of pea plant contained a mutation in the gene encoding thioredoxin that resulted in zero production of the protein thioredoxin.Another type contained two mutations: the same thioredoxin mutation as in the previous type and a mutation in the gene encoding the Calvin cycle enzyme phosphoribulokinase (PRK) that did not affect its expression.The third type contained no mutations in either gene and was designated as "wild type." Before the experiments, all plants were kept on a 14-hour light/10-hour dark cycle for several weeks.  In conducting the experiments, researchers excised leaves either toward the end of a light cycle or toward the end of a dark cycle.Chloroplasts were then isolated and lysed to release the contents of the stroma, and PRK was assayed to determine its catalytic activity.Which statement about thioredoxin is consistent with these data?

Quizplus · Accepted Answer

The data suggest that thioredoxin is involved in regulating the activity of PRK, as the mutant plants lacking thioredoxin had lower PRK activity. The fact that the PRK mutation did not affect its expression suggests that the decrease in activity is not due to a decrease in PRK levels, but rather to a lack of activation or regulation by thioredoxin. The observation that the experiments were conducted at different times of day further supports the idea that light-induced changes play a role in thioredoxin regulation, as the plants were likely in different stages of photosynthesis depending on the time of day. Overall, the data are consistent with thioredoxin being a regulatory molecule involved in the activation of PRK.

Refer to the Table Below Showing Observations from Experiments Conducted