Physician Assistant Scientific Knowledge 4

Question 1

Which genetic mutation pattern is associated with familial adenomatous polyposis (FAP)?

Accepted Answer

Autosomal dominant loss-of-function mutation in APC

Answer

FAP results from autosomal dominant loss-of-function mutations in the APC tumor suppressor gene, causing hundreds to thousands of colorectal polyps.

Question 2

Which mechanism allows viruses to evade the immune system by downregulating MHC class I expression?

Accepted Answer

Preventing cytotoxic T cells from recognizing infected cells

Answer

Downregulation of MHC class I prevents CD8+ cytotoxic T cells from recognizing viral peptides presented on infected cells, allowing viral persistence.

Question 3

In the coagulation cascade, which factor is shared between the intrinsic and extrinsic pathways at the common pathway junction?

Accepted Answer

Factor X

Answer

Factor X is activated by both the intrinsic pathway (via IXa/VIIIa) and the extrinsic pathway (via VIIa/TF) and initiates the common coagulation pathway.

Question 4

Which phase of pharmacokinetics involves the chemical transformation of a drug, typically in the liver?

Accepted Answer

Metabolism (biotransformation)

Answer

Metabolism (biotransformation) refers to enzymatic modification of drugs, primarily by cytochrome P450 enzymes in the liver, to facilitate elimination.

Question 5

The renin-angiotensin-aldosterone system (RAAS) is activated primarily by which stimulus?

Accepted Answer

Decreased renal perfusion pressure

Answer

Decreased renal perfusion pressure triggers juxtaglomerular cells to release renin, initiating the RAAS cascade to restore blood pressure and volume.

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Physician Assistant Practice Test

Physician Assistant Scientific Knowledge 4