Robbins Basic Pathology
10th Edition
Author(s)Vinay Kumar; MBBS; MD;
FRCPath; Abul K. Abbas; MBBS and
Jon C. Aster; MD; PhD
Print ISBN: 9780323353175
,Question 1
A laboratory study examines a cell in which histone proteins
surrounding a promoter region are extensively acetylated. Which
cellular effect is most likely to result from this modification?
A. Tighter chromatin condensation and reduced transcription
B. Increased accessibility of DNA to transcription factors
C. Increased degradation of messenger RNA in the cytoplasm
D. Direct conversion of DNA into protein
,Correct Answer: B. Increased accessibility of DNA to transcription
factors
Rationale: Histone acetylation generally relaxes chromatin structure,
making DNA more accessible to transcription machinery and
promoting gene expression. Tighter chromatin is associated more
closely with reduced transcription. Histone modification does not
directly degrade mRNA or convert DNA into protein.
Question 2
A child develops severe photosensitivity and multiple skin
abnormalities after minimal exposure to ultraviolet radiation. A defect
in DNA repair prevents removal of UV-induced DNA lesions. Which
cellular consequence best explains the increased risk of disease in this
patient?
A. Increased accuracy of DNA replication
B. Accumulation of mutations in cellular DNA
C. Increased mitochondrial ATP production
D. Enhanced degradation of extracellular collagen
Correct Answer: B. Accumulation of mutations in cellular DNA
Rationale: Failure to repair DNA damage allows mutations to
accumulate, increasing genomic instability and the risk of cellular
dysfunction and malignancy. DNA repair mechanisms normally
preserve genomic integrity. The defect would not improve replication
accuracy or directly alter mitochondrial ATP production or
extracellular collagen degradation.
Question 3
A tumor cell is found to contain multiple copies of a chromosomal
, region encoding a growth-promoting protein. Which genetic
abnormality most directly accounts for this finding?
A. Gene amplification
B. Point mutation causing a silent codon change
C. Increased protein ubiquitination
D. Reduced transcription of the affected gene
Correct Answer: A. Gene amplification
Rationale: Gene amplification increases the number of copies of a
particular gene and can produce excessive amounts of its encoded
protein, especially when the gene promotes cellular proliferation. A
silent mutation does not alter the encoded amino acid. Ubiquitination
affects protein turnover, whereas reduced transcription would
decrease gene expression.
Question 4
A cell exposed to a drug that blocks lysosomal enzyme function begins
accumulating partially degraded intracellular material. Which function
has been most directly impaired?
A. Protein translation on ribosomes
B. Degradation of cellular macromolecules within lysosomes
C. DNA replication in the nucleus
D. ATP production by glycolysis
Correct Answer: B. Degradation of cellular macromolecules within
lysosomes
Rationale: Lysosomes contain enzymes that digest proteins, lipids,
carbohydrates, and other cellular materials. Blocking these enzymes
causes undegraded material to accumulate within cells. Ribosomal
10th Edition
Author(s)Vinay Kumar; MBBS; MD;
FRCPath; Abul K. Abbas; MBBS and
Jon C. Aster; MD; PhD
Print ISBN: 9780323353175
,Question 1
A laboratory study examines a cell in which histone proteins
surrounding a promoter region are extensively acetylated. Which
cellular effect is most likely to result from this modification?
A. Tighter chromatin condensation and reduced transcription
B. Increased accessibility of DNA to transcription factors
C. Increased degradation of messenger RNA in the cytoplasm
D. Direct conversion of DNA into protein
,Correct Answer: B. Increased accessibility of DNA to transcription
factors
Rationale: Histone acetylation generally relaxes chromatin structure,
making DNA more accessible to transcription machinery and
promoting gene expression. Tighter chromatin is associated more
closely with reduced transcription. Histone modification does not
directly degrade mRNA or convert DNA into protein.
Question 2
A child develops severe photosensitivity and multiple skin
abnormalities after minimal exposure to ultraviolet radiation. A defect
in DNA repair prevents removal of UV-induced DNA lesions. Which
cellular consequence best explains the increased risk of disease in this
patient?
A. Increased accuracy of DNA replication
B. Accumulation of mutations in cellular DNA
C. Increased mitochondrial ATP production
D. Enhanced degradation of extracellular collagen
Correct Answer: B. Accumulation of mutations in cellular DNA
Rationale: Failure to repair DNA damage allows mutations to
accumulate, increasing genomic instability and the risk of cellular
dysfunction and malignancy. DNA repair mechanisms normally
preserve genomic integrity. The defect would not improve replication
accuracy or directly alter mitochondrial ATP production or
extracellular collagen degradation.
Question 3
A tumor cell is found to contain multiple copies of a chromosomal
, region encoding a growth-promoting protein. Which genetic
abnormality most directly accounts for this finding?
A. Gene amplification
B. Point mutation causing a silent codon change
C. Increased protein ubiquitination
D. Reduced transcription of the affected gene
Correct Answer: A. Gene amplification
Rationale: Gene amplification increases the number of copies of a
particular gene and can produce excessive amounts of its encoded
protein, especially when the gene promotes cellular proliferation. A
silent mutation does not alter the encoded amino acid. Ubiquitination
affects protein turnover, whereas reduced transcription would
decrease gene expression.
Question 4
A cell exposed to a drug that blocks lysosomal enzyme function begins
accumulating partially degraded intracellular material. Which function
has been most directly impaired?
A. Protein translation on ribosomes
B. Degradation of cellular macromolecules within lysosomes
C. DNA replication in the nucleus
D. ATP production by glycolysis
Correct Answer: B. Degradation of cellular macromolecules within
lysosomes
Rationale: Lysosomes contain enzymes that digest proteins, lipids,
carbohydrates, and other cellular materials. Blocking these enzymes
causes undegraded material to accumulate within cells. Ribosomal
