NUR 555 Quiz 9 SNHU Exam1 |Latest Updates
2026|2027|A Comprehensive Review Of 200
Practice Questions with Answers and Rationales|
Brand New Version!!!
Muscular Dystrophies and Genetic Inheritance
1. A child is diagnosed with Duchenne muscular dystrophy, and the parents ask
how this condition was inherited. Which statement by the healthcare
professional is most accurate?
A. X-linked recessive inheritance
B. Common SMN1 gene abnormality
C. Autosomal dominant inheritance
D. Inheritance is not well defined
Answer: A
Rationale: Duchenne muscular dystrophy results from a deletion or single-gene
defect on the short arm of the X chromosome, making it an X-linked recessive
disorder. Spinal muscular atrophy is linked to SMN1 gene abnormalities, and
facioscapulohumeral muscular dystrophy follows autosomal dominant
inheritance.
2. Which inheritance pattern is associated with spinal muscular atrophy (SMA)?
A. X-linked recessive
B. Autosomal dominant
C. Autosomal recessive
D. Mitochondrial
Answer: C
Rationale: SMA is an autosomal recessive disorder caused by mutations in the
SMN1 gene located on chromosome 5q13. Most patients demonstrate
homozygous deletion of SMN1.
,3. Facioscapulohumeral muscular dystrophy (FSHMD) is inherited via which
pattern?
A. X-linked recessive
B. Autosomal dominant
C. Autosomal recessive
D. Spontaneous mutation only
Answer: B
Rationale: FSHMD is an autosomal dominant disorder caused by a deletion on the
long arm of chromosome 4 at the 4q35 locus. In up to 30% of patients, the
mutation is de novo.
4. A parent asks about the genetic basis of Duchenne muscular dystrophy. Which
gene is primarily implicated?
A. SMN1 gene
B. DMD gene on Xp21
C. D4Z4 repeat on chromosome 4
D. PAX2 gene
Answer: B
Rationale: DMD is caused by mutations in the DMD gene located on the short arm
of the X chromosome at Xp21.2–Xp21.1. This is one of the largest human genes.
5. What percentage of facioscapulohumeral muscular dystrophy cases arise from
de novo mutations?
A. Less than 5%
B. Up to 30%
C. Approximately 50%
D. Nearly 100%
Answer: B
Rationale: In up to 30% of patients with FSHMD, the mutation is de novo
(sporadic) rather than inherited from a parent.
,6. The pathophysiology of Duchenne muscular dystrophy involves the absence
of which protein?
A. SMN protein
B. Dystrophin
C. Myosin
D. Actin
Answer: B
Rationale: DMD results from mutations affecting production of full-length
dystrophin (Dp427). The absence of dystrophin weakens the sarcolemma and
leads to myofiber necrosis.
7. Which statement best describes the function of dystrophin in normal muscle?
A. It facilitates neurotransmitter release at the neuromuscular junction
B. It links the cytoskeleton to the extracellular matrix, providing structural stability
C. It regulates calcium storage within the sarcoplasmic reticulum
D. It serves as the primary contractile protein in muscle fibers
Answer: B
Rationale: Dystrophin is a large structural protein that links the cytoskeleton to
the sarcolemma-anchored dystrophin-associated protein complex, which connects
to the basal lamina and extracellular matrix.
8. What is the primary pathophysiological event in Duchenne muscular
dystrophy?
A. Demyelination of motor neurons
B. Myofiber necrosis
C. Impaired acetylcholine receptor function
D. Mitochondrial dysfunction
Answer: B
Rationale: Myofiber necrosis is the main pathophysiological event in DMD. The
weakened sarcolemma tears under mechanical stress, leading to muscle fiber
death.
, 9. A child with Duchenne muscular dystrophy experiences progressive
weakness. Which mechanism explains the worsening of muscle function?
A. Accumulation of toxic metabolites
B. Repeated cycles of necrosis and insufficient regeneration
C. Autoimmune destruction of muscle fibers
D. Chronic ischemia from vascular insufficiency
Answer: B
Rationale: The absence of dystrophin leads to repeated cycles of myofiber
necrosis and regeneration that eventually become insufficient, resulting in
progressive muscle weakness and replacement by fibrotic and adipose tissue.
10. Which of the following distinguishes Becker muscular dystrophy from
Duchenne muscular dystrophy?
A. Becker MD involves residual dystrophin expression
B. Becker MD is X-linked dominant
C. Becker MD affects only females
D. Becker MD involves the SMN1 gene
Answer: A
Rationale: The severity of the muscle phenotype depends on whether mutations
result in complete absence of dystrophin (DMD) or residual dystrophin synthesis
(Becker MD, which is milder).
11. A 4-year-old boy with Duchenne muscular dystrophy is at risk for cardiac
complications. Which mechanism explains this?
A. Dystrophin isoforms are expressed in cardiac tissue
B. Cardiac muscle relies entirely on dystrophin for contraction
C. Cardiomyopathy results from respiratory failure
D. Cardiac involvement is secondary to immobility
Answer: A
Rationale: Different dystrophin isoforms are expressed in cardiac tissue, and
2026|2027|A Comprehensive Review Of 200
Practice Questions with Answers and Rationales|
Brand New Version!!!
Muscular Dystrophies and Genetic Inheritance
1. A child is diagnosed with Duchenne muscular dystrophy, and the parents ask
how this condition was inherited. Which statement by the healthcare
professional is most accurate?
A. X-linked recessive inheritance
B. Common SMN1 gene abnormality
C. Autosomal dominant inheritance
D. Inheritance is not well defined
Answer: A
Rationale: Duchenne muscular dystrophy results from a deletion or single-gene
defect on the short arm of the X chromosome, making it an X-linked recessive
disorder. Spinal muscular atrophy is linked to SMN1 gene abnormalities, and
facioscapulohumeral muscular dystrophy follows autosomal dominant
inheritance.
2. Which inheritance pattern is associated with spinal muscular atrophy (SMA)?
A. X-linked recessive
B. Autosomal dominant
C. Autosomal recessive
D. Mitochondrial
Answer: C
Rationale: SMA is an autosomal recessive disorder caused by mutations in the
SMN1 gene located on chromosome 5q13. Most patients demonstrate
homozygous deletion of SMN1.
,3. Facioscapulohumeral muscular dystrophy (FSHMD) is inherited via which
pattern?
A. X-linked recessive
B. Autosomal dominant
C. Autosomal recessive
D. Spontaneous mutation only
Answer: B
Rationale: FSHMD is an autosomal dominant disorder caused by a deletion on the
long arm of chromosome 4 at the 4q35 locus. In up to 30% of patients, the
mutation is de novo.
4. A parent asks about the genetic basis of Duchenne muscular dystrophy. Which
gene is primarily implicated?
A. SMN1 gene
B. DMD gene on Xp21
C. D4Z4 repeat on chromosome 4
D. PAX2 gene
Answer: B
Rationale: DMD is caused by mutations in the DMD gene located on the short arm
of the X chromosome at Xp21.2–Xp21.1. This is one of the largest human genes.
5. What percentage of facioscapulohumeral muscular dystrophy cases arise from
de novo mutations?
A. Less than 5%
B. Up to 30%
C. Approximately 50%
D. Nearly 100%
Answer: B
Rationale: In up to 30% of patients with FSHMD, the mutation is de novo
(sporadic) rather than inherited from a parent.
,6. The pathophysiology of Duchenne muscular dystrophy involves the absence
of which protein?
A. SMN protein
B. Dystrophin
C. Myosin
D. Actin
Answer: B
Rationale: DMD results from mutations affecting production of full-length
dystrophin (Dp427). The absence of dystrophin weakens the sarcolemma and
leads to myofiber necrosis.
7. Which statement best describes the function of dystrophin in normal muscle?
A. It facilitates neurotransmitter release at the neuromuscular junction
B. It links the cytoskeleton to the extracellular matrix, providing structural stability
C. It regulates calcium storage within the sarcoplasmic reticulum
D. It serves as the primary contractile protein in muscle fibers
Answer: B
Rationale: Dystrophin is a large structural protein that links the cytoskeleton to
the sarcolemma-anchored dystrophin-associated protein complex, which connects
to the basal lamina and extracellular matrix.
8. What is the primary pathophysiological event in Duchenne muscular
dystrophy?
A. Demyelination of motor neurons
B. Myofiber necrosis
C. Impaired acetylcholine receptor function
D. Mitochondrial dysfunction
Answer: B
Rationale: Myofiber necrosis is the main pathophysiological event in DMD. The
weakened sarcolemma tears under mechanical stress, leading to muscle fiber
death.
, 9. A child with Duchenne muscular dystrophy experiences progressive
weakness. Which mechanism explains the worsening of muscle function?
A. Accumulation of toxic metabolites
B. Repeated cycles of necrosis and insufficient regeneration
C. Autoimmune destruction of muscle fibers
D. Chronic ischemia from vascular insufficiency
Answer: B
Rationale: The absence of dystrophin leads to repeated cycles of myofiber
necrosis and regeneration that eventually become insufficient, resulting in
progressive muscle weakness and replacement by fibrotic and adipose tissue.
10. Which of the following distinguishes Becker muscular dystrophy from
Duchenne muscular dystrophy?
A. Becker MD involves residual dystrophin expression
B. Becker MD is X-linked dominant
C. Becker MD affects only females
D. Becker MD involves the SMN1 gene
Answer: A
Rationale: The severity of the muscle phenotype depends on whether mutations
result in complete absence of dystrophin (DMD) or residual dystrophin synthesis
(Becker MD, which is milder).
11. A 4-year-old boy with Duchenne muscular dystrophy is at risk for cardiac
complications. Which mechanism explains this?
A. Dystrophin isoforms are expressed in cardiac tissue
B. Cardiac muscle relies entirely on dystrophin for contraction
C. Cardiomyopathy results from respiratory failure
D. Cardiac involvement is secondary to immobility
Answer: A
Rationale: Different dystrophin isoforms are expressed in cardiac tissue, and
