SAT Subject Biology Practice Question 426: Answer and Explanation
16. Unfertilized frog oocytes were bathed in a neutral, isotonic solution (Frog Ringer's solution) to prevent changes in volume due to osmosis. The Frog Ringer's solution was supplemented with radiolabeled amino acids. A sample of oocytes was taken every 30 minutes and assayed for radioactivity.
At Time 1, the oocytes were fertilized. Samples were taken at five-minute intervals after fertilization and assayed for radioactivity. The results are presented in the graph below.
How could a control be created for this experiment?
A. Immerse the oocytes in non-radiolabeled Frog Ringer's solution prior to fertilization
B. Sample the oocytes at five-minute intervals prior to fertilization
C. Sample the oocytes at 30-minute intervals after fertilization
D. Divide the oocytes into two groups, immerse one group in non-radiolabeled Frog Ringer's solution and one group in radiolabeled solution
E. Divide the oocytes into two groups, fertilize one group, and simulate fertilization in the other, but do not actually introduce sperm into the oocytes
Correct Answer: E
E Remember that a control is subjected to everything the experimental group is, except for the item being tested. The experiment in this case is testing the effect of fertilization on protein synthesis. A control group should be exposed to everything the experimental group is except for the actual fertilization.