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 patient has a mutation that prevents a DNA-binding transcription
factor from attaching to its target regulatory sequence. Which cellular
process would be most directly impaired?
A. Translation of preexisting messenger RNA
B. Regulation of gene transcription
C. Assembly of extracellular collagen fibers
D. Oxidative phosphorylation
Correct Answer: B. Regulation of gene transcription
,Rationale: DNA-binding transcription factors regulate gene expression
by interacting with specific regulatory DNA sequences and influencing
transcription. Loss of this interaction can prevent appropriate
production of the affected messenger RNA. A is controlled primarily at
the level of translation, C involves extracellular matrix organization, and
D occurs in mitochondria.
Question 2
A researcher identifies a mutation that changes a single nucleotide in a
gene but does not alter the amino acid sequence of the encoded
protein. Which type of mutation has most likely occurred?
A. Missense mutation
B. Nonsense mutation
C. Silent mutation
D. Frameshift mutation
Correct Answer: C. Silent mutation
Rationale: A silent mutation changes a nucleotide without changing the
encoded amino acid, usually because multiple codons can specify the
same amino acid. A missense mutation changes an amino acid, whereas
a nonsense mutation creates a premature stop codon. A frameshift
results from insertion or deletion of nucleotides that alters the
downstream reading frame.
Question 3
A cell is exposed to a toxic substance that damages nuclear DNA. Before
the cell proceeds through the cell cycle, which response is most
important for maintaining genomic integrity?
, A. Immediate stimulation of protein synthesis
B. Activation of mechanisms that detect and repair DNA damage
C. Increased secretion of extracellular matrix proteins
D. Increased breakdown of glucose
Correct Answer: B. Activation of mechanisms that detect and repair
DNA damage
Rationale: Cells possess surveillance and repair systems that identify
DNA damage and help restore genomic integrity before replication or
division proceeds. Failure of these mechanisms can allow mutations to
accumulate. Protein synthesis, extracellular matrix production, and
glucose breakdown may change during cellular stress but do not
directly correct nuclear DNA damage.
Question 4
A secretory cell synthesizes a protein that will be exported outside the
cell. Which organelle is primarily responsible for synthesizing this
protein?
A. Smooth endoplasmic reticulum
B. Rough endoplasmic reticulum
C. Lysosome
D. Peroxisome
Correct Answer: B. Rough endoplasmic reticulum
Rationale: Proteins destined for secretion are synthesized by ribosomes
attached to the rough endoplasmic reticulum and then enter the
secretory pathway. The smooth endoplasmic reticulum is more involved
in lipid synthesis and other metabolic functions. Lysosomes perform
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 patient has a mutation that prevents a DNA-binding transcription
factor from attaching to its target regulatory sequence. Which cellular
process would be most directly impaired?
A. Translation of preexisting messenger RNA
B. Regulation of gene transcription
C. Assembly of extracellular collagen fibers
D. Oxidative phosphorylation
Correct Answer: B. Regulation of gene transcription
,Rationale: DNA-binding transcription factors regulate gene expression
by interacting with specific regulatory DNA sequences and influencing
transcription. Loss of this interaction can prevent appropriate
production of the affected messenger RNA. A is controlled primarily at
the level of translation, C involves extracellular matrix organization, and
D occurs in mitochondria.
Question 2
A researcher identifies a mutation that changes a single nucleotide in a
gene but does not alter the amino acid sequence of the encoded
protein. Which type of mutation has most likely occurred?
A. Missense mutation
B. Nonsense mutation
C. Silent mutation
D. Frameshift mutation
Correct Answer: C. Silent mutation
Rationale: A silent mutation changes a nucleotide without changing the
encoded amino acid, usually because multiple codons can specify the
same amino acid. A missense mutation changes an amino acid, whereas
a nonsense mutation creates a premature stop codon. A frameshift
results from insertion or deletion of nucleotides that alters the
downstream reading frame.
Question 3
A cell is exposed to a toxic substance that damages nuclear DNA. Before
the cell proceeds through the cell cycle, which response is most
important for maintaining genomic integrity?
, A. Immediate stimulation of protein synthesis
B. Activation of mechanisms that detect and repair DNA damage
C. Increased secretion of extracellular matrix proteins
D. Increased breakdown of glucose
Correct Answer: B. Activation of mechanisms that detect and repair
DNA damage
Rationale: Cells possess surveillance and repair systems that identify
DNA damage and help restore genomic integrity before replication or
division proceeds. Failure of these mechanisms can allow mutations to
accumulate. Protein synthesis, extracellular matrix production, and
glucose breakdown may change during cellular stress but do not
directly correct nuclear DNA damage.
Question 4
A secretory cell synthesizes a protein that will be exported outside the
cell. Which organelle is primarily responsible for synthesizing this
protein?
A. Smooth endoplasmic reticulum
B. Rough endoplasmic reticulum
C. Lysosome
D. Peroxisome
Correct Answer: B. Rough endoplasmic reticulum
Rationale: Proteins destined for secretion are synthesized by ribosomes
attached to the rough endoplasmic reticulum and then enter the
secretory pathway. The smooth endoplasmic reticulum is more involved
in lipid synthesis and other metabolic functions. Lysosomes perform
