Medical Genetics & Molecular Medicine
Exam 2026 Edition Questions Correct
Answers & Detailed Rationales
1.
A 28-year-old woman with a family history of breast and
ovarian cancer is found to carry a pathogenic germline variant
in BRCA1. Which mechanism best explains the increased cancer
risk associated with this mutation?
A. Activation of a constitutively active tyrosine kinase
B. Impaired homologous recombination-mediated DNA repair
C. Increased telomerase degradation
D. Failure of mismatch repair exclusively in microsatellite
regions
Answer: B. Impaired homologous recombination-mediated
DNA repair
BRCA1 participates in homologous recombination, an important
pathway for repairing double-strand DNA breaks. Loss-of-
function variants cause genomic instability and increase
susceptibility to breast, ovarian, pancreatic, and prostate
cancers.
,2.
A child presents with developmental delay, hypotonia, and
characteristic facial features. Karyotyping reveals 47
chromosomes with an additional chromosome 21. What
genetic mechanism most commonly produces this condition?
A. Robertsonian translocation
B. Meiotic nondisjunction
C. Mitotic recombination
D. Uniparental disomy
Answer: B. Meiotic nondisjunction
Most cases of Down syndrome result from meiotic
nondisjunction, producing an extra chromosome 21. The risk
increases with advancing maternal age.
3.
A newborn has hypotonia, a weak cry, and difficulty feeding.
Genetic testing demonstrates deletion of the paternal 15q11-
q13 region. Which diagnosis is most likely?
A. Angelman syndrome
B. Prader-Willi syndrome
,C. DiGeorge syndrome
D. Williams syndrome
Answer: B. Prader-Willi syndrome
The paternal 15q11-q13 region contains genes that are
normally expressed from the paternal chromosome. Loss of
paternal expression produces Prader-Willi syndrome,
characterized by neonatal hypotonia, feeding difficulties, later
hyperphagia, obesity, and hypogonadism.
4.
A child has severe intellectual disability, seizures, ataxia,
inappropriate laughter, and a deletion involving the maternal
15q11-q13 region. Which condition is present?
A. Prader-Willi syndrome
B. Angelman syndrome
C. Fragile X syndrome
D. Rett syndrome
Answer: B. Angelman syndrome
Angelman syndrome results from loss of maternal expression of
UBE3A in the brain, commonly due to maternal deletion of
15q11-q13. The disorder features severe developmental
, impairment, seizures, ataxia, and characteristic behavioral
manifestations.
5.
A patient with Marfan syndrome has an abnormality involving
the FBN1 gene. Which protein is primarily affected?
A. Type I collagen
B. Fibrillin-1
C. Elastin
D. Laminin
Answer: B. Fibrillin-1
FBN1 encodes fibrillin-1, a structural component of extracellular
microfibrils that also regulates transforming growth factor-β
signaling. Mutations cause Marfan syndrome with skeletal,
ocular, and cardiovascular manifestations.
6.
A 5-year-old boy has recurrent infections, eczema, and
thrombocytopenia with small platelets. The disorder is caused
by a mutation affecting the WAS gene. What inheritance
pattern is expected?
Exam 2026 Edition Questions Correct
Answers & Detailed Rationales
1.
A 28-year-old woman with a family history of breast and
ovarian cancer is found to carry a pathogenic germline variant
in BRCA1. Which mechanism best explains the increased cancer
risk associated with this mutation?
A. Activation of a constitutively active tyrosine kinase
B. Impaired homologous recombination-mediated DNA repair
C. Increased telomerase degradation
D. Failure of mismatch repair exclusively in microsatellite
regions
Answer: B. Impaired homologous recombination-mediated
DNA repair
BRCA1 participates in homologous recombination, an important
pathway for repairing double-strand DNA breaks. Loss-of-
function variants cause genomic instability and increase
susceptibility to breast, ovarian, pancreatic, and prostate
cancers.
,2.
A child presents with developmental delay, hypotonia, and
characteristic facial features. Karyotyping reveals 47
chromosomes with an additional chromosome 21. What
genetic mechanism most commonly produces this condition?
A. Robertsonian translocation
B. Meiotic nondisjunction
C. Mitotic recombination
D. Uniparental disomy
Answer: B. Meiotic nondisjunction
Most cases of Down syndrome result from meiotic
nondisjunction, producing an extra chromosome 21. The risk
increases with advancing maternal age.
3.
A newborn has hypotonia, a weak cry, and difficulty feeding.
Genetic testing demonstrates deletion of the paternal 15q11-
q13 region. Which diagnosis is most likely?
A. Angelman syndrome
B. Prader-Willi syndrome
,C. DiGeorge syndrome
D. Williams syndrome
Answer: B. Prader-Willi syndrome
The paternal 15q11-q13 region contains genes that are
normally expressed from the paternal chromosome. Loss of
paternal expression produces Prader-Willi syndrome,
characterized by neonatal hypotonia, feeding difficulties, later
hyperphagia, obesity, and hypogonadism.
4.
A child has severe intellectual disability, seizures, ataxia,
inappropriate laughter, and a deletion involving the maternal
15q11-q13 region. Which condition is present?
A. Prader-Willi syndrome
B. Angelman syndrome
C. Fragile X syndrome
D. Rett syndrome
Answer: B. Angelman syndrome
Angelman syndrome results from loss of maternal expression of
UBE3A in the brain, commonly due to maternal deletion of
15q11-q13. The disorder features severe developmental
, impairment, seizures, ataxia, and characteristic behavioral
manifestations.
5.
A patient with Marfan syndrome has an abnormality involving
the FBN1 gene. Which protein is primarily affected?
A. Type I collagen
B. Fibrillin-1
C. Elastin
D. Laminin
Answer: B. Fibrillin-1
FBN1 encodes fibrillin-1, a structural component of extracellular
microfibrils that also regulates transforming growth factor-β
signaling. Mutations cause Marfan syndrome with skeletal,
ocular, and cardiovascular manifestations.
6.
A 5-year-old boy has recurrent infections, eczema, and
thrombocytopenia with small platelets. The disorder is caused
by a mutation affecting the WAS gene. What inheritance
pattern is expected?
