A study question tests what you can conclude from the groups researchers compared. Read the sentence leading into the blank to see what kind of conclusion it asks for. When researchers remove a protein and restore it in different places, pair each change with its result, including early and later results. Then ask what each restoration can show about where the protein needs to act. Predict only what the results show, without extending a measured result into a broader claim.
Hints
- Hint 1
Start with the comparison after the pots were rotated. Compare the groups at the first signs of bending and again at 24 hours.
- Hint 2
In the restoration tests, look for where GRV1 was restored in each group. What did each location do to the delay?
- Hint 3
Each restoration starts with a knockout seedling. Ask where GRV1 is still absent, and connect that to the timing result.
Step-by-step
Compare timing, then test each region
Step 1Compare when bending begins
The GRV1-knockout seedlings lack GRV1, so let's compare their roots with unmodified roots to find the study's conclusion. How does bending differ after the pots turn? Unmodified roots begin bending within 3 hours, but knockout roots don't show noticeable bending until 12 hours later. Removing GRV1 delays the start of bending.
- Step 2
Check the 24-hour result
At 24 hours, both groups have the same average bend angle and total root length, so the difference is in timing, not the measured angle or length. What do those equal results rule out? The choice about both how soon and how far adds an angle difference, while a general promoter of root elongation claims a broad growth role these lengths don't show.
- Step 3
Track the two restorations
Now GRV1 is restored in only one of two regions in separate knockout seedlings: the gravity-sensing cap or the elongation zone, where growth bends the root. Which restoration removes the delay? Root-cap restoration brings back normal timing, while restoring GRV1 in the elongation zone did not shorten the delay.
- Step 4
Infer where GRV1 needs to act
Does GRV1 have to act in the elongation zone for bending to start at the normal time? Since GRV1 was restored in only one of two regions, the cap-only seedlings regain normal timing while still lacking GRV1 in the elongation zone. That rules out must be active in the elongation zone and supports the choice about rapid gravitropic bending: GRV1's contribution depends on its activity in the gravity-sensing cap, not its direct activity in the elongation zone. Choice D.