To determine whether a signal sequence directs proteins to a particular organelle, researchers prepare two versions of the same protein: one version contains the signal sequence, while the other lacks it. They label the protein that contains the signal sequence with a radioactive marker, and then incubate both of the proteins with the organelle of interest.
After allowing enough time for any of the proteins to be transported into the organelle, a protease is added to the mixture.
If the signal sequence is the correct one for the selected organelle, what would the researchers likely see?
A. The radioactive label would be associated with an intact protein.
B. The radioactive label would be associated with the protease.
C. The radioactive label would be associated with one particular protein fragment.
D. The radioactive label would be destroyed.

The protease is an enzyme that digest proteins. When added to the mixture of proteins and the organelle the protease would destroy not only the protein that is labeled with a radioactive marker but also the unmarked one. The radioactive label can be found with the protease when this has already destroyed the protein.