Robbins Basic Pathology
10th Edition
Author(s)Vinay Kumar; Abul K. Abbas;
Jon C. Aster
TEST BANK
Ch. 1 — The Cell as a Unit of Health and Disease — The
Genome
Question Stem: A 28-year-old woman has recurrent infections
and is found to have impaired neutrophil oxidative burst.
Genetic sequencing reveals a single-base substitution in a gene
that encodes a critical electron transport enzyme in phagocytes.
Which molecular mechanism best explains how this point
mutation most likely produces a dysfunctional enzyme?
A. Frameshift leading to truncated protein
B. Missense mutation altering amino-acid side chain and
enzyme active site
,C. Nonsense mutation creating a premature stop codon
D. Silent mutation changing codon without amino-acid
substitution
Correct Answer: B
Rationales — Correct: A missense mutation replaces one amino
acid with another, which can change the enzyme’s active-site
geometry or chemical properties and impair electron transfer
required for oxidative burst.
Rationales — Incorrect: A: Frameshifts typically result from
insertions/deletions, not single-base substitutions, and produce
widespread protein alteration. C: Nonsense mutation produces
truncation; not the most likely in single-base substitution that
preserves length. D: Silent mutation does not change amino
acid identity and therefore usually does not alter enzyme
function.
Teaching Point: Missense mutations can disrupt enzyme active
sites and protein function.
Citation: Kumar et al. (2021). Robbins Basic Pathology (10th
Ed.). Ch. 1.
Ch. 1 — The Cell as a Unit of Health and Disease — The
Genome
Question Stem: During counseling, a patient asks why some
chromosomal deletions cause severe disease while others have
little phenotype. Which genomic principle best explains variable
,phenotypic effects of deletions?
A. Dosage sensitivity of haploinsufficient genes in the deleted
region
B. Universal compensation by homologous chromosomes
C. Chromosomal deletions never affect regulatory elements
D. Deletion size is the sole determinant of phenotypic severity
Correct Answer: A
Rationales — Correct: Haploinsufficient genes require two
functional copies; deletion of one copy reduces product below a
critical threshold, causing disease manifestation.
Rationales — Incorrect: B: Homologous chromosomes do not
universally compensate; many genes are dosage-sensitive. C:
Deletions can remove regulatory elements, affecting gene
expression widely. D: Deletion size matters, but phenotypic
severity depends on which genes (especially dosage-sensitive
ones) are lost.
Teaching Point: Haploinsufficiency causes disease when single-
copy gene expression is insufficient.
Citation: Kumar et al. (2021). Robbins Basic Pathology (10th
Ed.). Ch. 1.
Ch. 1 — The Cell as a Unit of Health and Disease — Cellular
Housekeeping
Question Stem: A patient’s biopsy shows accumulation of
lipofuscin pigment in long-lived cardiomyocytes. Which cellular
, process is most directly responsible for degrading the worn-out
organelles that, when impaired, leads to pigment
accumulation?
A. Autophagy-lysosomal pathway
B. Ubiquitin-proteasome system for extracellular proteins
C. Endocytosis of plasma membrane receptors
D. Exocytosis of glycoproteins
Correct Answer: A
Rationales — Correct: Autophagy delivers damaged organelles
and intracellular debris to lysosomes for degradation; impaired
autophagy/lysosomal function leads to accumulation of residual
bodies like lipofuscin.
Rationales — Incorrect: B: Ubiquitin-proteasome system
primarily degrades short-lived and misfolded proteins, not bulk
organelles. C: Endocytosis internalizes membrane components
but is not the main pathway for organelle turnover. D:
Exocytosis secretes materials and does not degrade intracellular
organelles.
Teaching Point: Autophagy–lysosome dysfunction causes
intracellular pigment accumulation.
Citation: Kumar et al. (2021). Robbins Basic Pathology (10th
Ed.). Ch. 1.
Ch. 1 — The Cell as a Unit of Health and Disease — Cellular
Housekeeping
10th Edition
Author(s)Vinay Kumar; Abul K. Abbas;
Jon C. Aster
TEST BANK
Ch. 1 — The Cell as a Unit of Health and Disease — The
Genome
Question Stem: A 28-year-old woman has recurrent infections
and is found to have impaired neutrophil oxidative burst.
Genetic sequencing reveals a single-base substitution in a gene
that encodes a critical electron transport enzyme in phagocytes.
Which molecular mechanism best explains how this point
mutation most likely produces a dysfunctional enzyme?
A. Frameshift leading to truncated protein
B. Missense mutation altering amino-acid side chain and
enzyme active site
,C. Nonsense mutation creating a premature stop codon
D. Silent mutation changing codon without amino-acid
substitution
Correct Answer: B
Rationales — Correct: A missense mutation replaces one amino
acid with another, which can change the enzyme’s active-site
geometry or chemical properties and impair electron transfer
required for oxidative burst.
Rationales — Incorrect: A: Frameshifts typically result from
insertions/deletions, not single-base substitutions, and produce
widespread protein alteration. C: Nonsense mutation produces
truncation; not the most likely in single-base substitution that
preserves length. D: Silent mutation does not change amino
acid identity and therefore usually does not alter enzyme
function.
Teaching Point: Missense mutations can disrupt enzyme active
sites and protein function.
Citation: Kumar et al. (2021). Robbins Basic Pathology (10th
Ed.). Ch. 1.
Ch. 1 — The Cell as a Unit of Health and Disease — The
Genome
Question Stem: During counseling, a patient asks why some
chromosomal deletions cause severe disease while others have
little phenotype. Which genomic principle best explains variable
,phenotypic effects of deletions?
A. Dosage sensitivity of haploinsufficient genes in the deleted
region
B. Universal compensation by homologous chromosomes
C. Chromosomal deletions never affect regulatory elements
D. Deletion size is the sole determinant of phenotypic severity
Correct Answer: A
Rationales — Correct: Haploinsufficient genes require two
functional copies; deletion of one copy reduces product below a
critical threshold, causing disease manifestation.
Rationales — Incorrect: B: Homologous chromosomes do not
universally compensate; many genes are dosage-sensitive. C:
Deletions can remove regulatory elements, affecting gene
expression widely. D: Deletion size matters, but phenotypic
severity depends on which genes (especially dosage-sensitive
ones) are lost.
Teaching Point: Haploinsufficiency causes disease when single-
copy gene expression is insufficient.
Citation: Kumar et al. (2021). Robbins Basic Pathology (10th
Ed.). Ch. 1.
Ch. 1 — The Cell as a Unit of Health and Disease — Cellular
Housekeeping
Question Stem: A patient’s biopsy shows accumulation of
lipofuscin pigment in long-lived cardiomyocytes. Which cellular
, process is most directly responsible for degrading the worn-out
organelles that, when impaired, leads to pigment
accumulation?
A. Autophagy-lysosomal pathway
B. Ubiquitin-proteasome system for extracellular proteins
C. Endocytosis of plasma membrane receptors
D. Exocytosis of glycoproteins
Correct Answer: A
Rationales — Correct: Autophagy delivers damaged organelles
and intracellular debris to lysosomes for degradation; impaired
autophagy/lysosomal function leads to accumulation of residual
bodies like lipofuscin.
Rationales — Incorrect: B: Ubiquitin-proteasome system
primarily degrades short-lived and misfolded proteins, not bulk
organelles. C: Endocytosis internalizes membrane components
but is not the main pathway for organelle turnover. D:
Exocytosis secretes materials and does not degrade intracellular
organelles.
Teaching Point: Autophagy–lysosome dysfunction causes
intracellular pigment accumulation.
Citation: Kumar et al. (2021). Robbins Basic Pathology (10th
Ed.). Ch. 1.
Ch. 1 — The Cell as a Unit of Health and Disease — Cellular
Housekeeping
