Repeated USMLE Questions Step 1- Review- 60

Q- In a case of blood flow obstruction to an alveolus, which of the following changes in ventilation/perfusion ratio, Po2 in the alveoli and Pco2 in the alveoli respectively most likely occur?

A- decreases/decreases/decreases

B- decreases/decreases/increases

C- increases/decreases/decreases

D- increases/increases/decreases

D- increases/increases/decreases- This is a simple and very important question in the USMLE. Blood flow obstruction means low perfusion. Ventilation is normal so; the ratio increases and so Po2.

Q- Which one of the following is the function of retinoblastoma gene in a normal person?

A- It codes for GAP

B- It inactivates P21

C- It prevents apoptosis

D- It stops the cell cycle before S phase

D- It stops the cell cycle before S phase- Tumor suppressor genes such as retinoblastoma, p53, APC and NF-1 code for proteins to suppress cellular proliferation. Rb gene stops the cell cycle between G1 and S.

Q- A mass is found in an abdominal CT scan of a 54-year-old woman. Which of the following indicates that this mass is malignant?

A- Cellular necrosis

B- Invasion

C- Presence of mitosis

D- Size of the mass

B- Invasion- This is the only one on the list that is particular for malignancies. Other signs can be found but not specific.

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2 thoughts on “Repeated USMLE Questions Step 1- Review- 60”

  1. Thank you Dr. Mohamed. I appreciate your feedback.

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