Which statement describes evidence that supports the signal hypothesis as an explanation for how secretory proteins are targeted to the rough ER?
A) The protein is larger when synthesized in vitro on free polysomes.
B) The secretory protein ends up in the cytosol when a short sequence is deleted by genetic engineering.
C) A normally cytosolic protein is secreted when a specific sequence is added to it by genetic engineering.
D) All of the above

Question

Quizplus · Accepted Answer

The signal hypothesis is supported by all the given statements: A) indicates that proteins synthesized on free polysomes (without ER targeting) are larger because they include a signal sequence that is normally removed in the ER; B) shows that removing the signal sequence (which targets the protein to the ER) results in the protein remaining in the cytosol, indicating the importance of the signal sequence for ER targeting; C) demonstrates that adding a signal sequence to a normally cytosolic protein can reroute it to be secreted, further supporting the role of the signal sequence in directing proteins to the ER.

Which Statement Describes Evidence That Supports the Signal Hypothesis as an Explanation