SAT Subject Biology Practice Question 463: Answer and Explanation
13. Questions below refers to the following experiment involving human liver cells.
Aspartate aminotransferase (AAT) is an enzyme produced in liver cells that catalyzes an important step in the metabolism of amino acids. The production of AAT is dependent upon various hormonal stimuli. Human liver cells were cultured; half the cultured cells were used to measure the amount of AAT mRNA present, and half were used to measure the amount of AAT present. Measurements were taken at five-minute intervals following hormonal stimulation of the cells.
Figure 1 shows the results of this experiment.
The experiment was repeated, this time adding an inhibitor of protein synthesis along with the hormone.
Figure 2 shows the results of this experiment.
A. Immediately upon addition of hormone
B. 1 minute after addition of hormone
C. 3 minutes after addition of hormone
D. 8 minutes after addition of hormone
E. 20 minutes after addition of hormone
Correct Answer: B
B Radiolabeled uracil would be incorporated into mRNA and so would be detected as soon as mRNA were present-at approximately one minute after the addition of hormone.