Physician Assistant Scientific Knowledge 4 — Questions and Answers
Question 1: Which genetic mutation pattern is associated with familial adenomatous polyposis (FAP)?
- Autosomal dominant loss-of-function mutation in APC (Correct answer)
- Autosomal recessive mutation in MLH1
- X-linked dominant mutation in BRCA2
- Trinucleotide repeat expansion in TP53
Correct answer: Autosomal dominant loss-of-function mutation in APC
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?
- Preventing cytotoxic T cells from recognizing infected cells (Correct answer)
- Blocking B cell antibody production
- Inhibiting complement activation
- Suppressing natural killer cell activity
Correct answer: Preventing cytotoxic T cells from recognizing infected cells
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?
- Factor X (Correct answer)
- Factor VII
- Factor XII
- Factor IX
Correct answer: Factor X
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?
- Metabolism (biotransformation) (Correct answer)
- Distribution
- Absorption
- Excretion
Correct answer: Metabolism (biotransformation)
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?
- Decreased renal perfusion pressure (Correct answer)
- Hyperkalemia alone
- Increased atrial natriuretic peptide
- Elevated serum sodium
Correct answer: Decreased renal perfusion pressure
Decreased renal perfusion pressure triggers juxtaglomerular cells to release renin, initiating the RAAS cascade to restore blood pressure and volume.
Question 6: In genetics, incomplete dominance results in which pattern of inheritance?
- Intermediate phenotype in heterozygotes (Correct answer)
- One allele completely masks the other
- Both alleles are fully expressed simultaneously
- Expression varies by sex of the offspring
Correct answer: Intermediate phenotype in heterozygotes
Incomplete dominance produces an intermediate phenotype in heterozygotes, as neither allele fully dominates the other (e.g., red × white = pink flowers).
Question 7: Which organelle is responsible for protein sorting, post-translational modifications, and packaging for secretion?
- Golgi apparatus (Correct answer)
- Smooth endoplasmic reticulum
- Rough endoplasmic reticulum
- Lysosome
Correct answer: Golgi apparatus
The Golgi apparatus receives proteins from the RER, performs glycosylation and other modifications, and sorts them into vesicles for secretion or intracellular delivery.
Physician Assistant Scientific Knowledge 4
Which genetic mutation pattern is associated with familial adenomatous polyposis (FAP)?