USMLE Step 1 Question 362

Question:

A 30 year old man comes to emergency room complaining of right upper quadrant pain. He had just returned from a two week trip to Italy. One day after taking a tour of the Italian countryside, he began having diarrhea and abdominal pain that subsided within 24 hours. On physical exam, he is ill appearing and short of breath. He has a moderate amount of jaundice. Upon further questioning, he admits to eating mushrooms while on his tour of the Italian countryside. A urinalysis is performed and he is found to have alphaamanitin, an inhibitor of RNA polymerase II. The synthesis of which of the following would most likely be affected?

Correct Answer: C.  mRNA

Alpha-amanitin is found in death cap mushrooms. These types of mushrooms are native to Europe and are widespread. Early symptoms of intoxication are diarrhea and cramping which subside within the first day. This can give a false sense of remission.

Intoxication eventually leads to renal failure, respiratory failure, and eventually death within the first week after ingestion. RNA polymerase II is responsible for the synthesis of mRNA (choice C). RNA polymerase I makes rRNA (choice D) and RNA polymerase III makes tRNA (choice E).

RNA polymerases do not make DNA (choice B).

cDNA (choice A) is not naturally occurring in the body. It is made in the laboratory and is a copy of all mRNA encoding regions present in cells. It is tissue specific and expresses genes found only in the tissue from which it is derived.