Gastroenterology and Hematobiliary Pathophysiology Prep
with Detailed Rationales
Course Code: NURS 5304
Course Name: Advanced Pathophysiology II
Topic: Advanced Genetics, Tumor Biology, Hemoglobinopathies, Viral Hepatitis,
and Nonalcoholic Fatty Liver Disease (NAFLD)
Academic Year: 2026/2027
Question 1
A mother is a confirmed carrier for the X-linked recessive Emery-Dreifuss
muscular dystrophy gene. The father has not been tested but is completely
asymptomatic and does not exhibit upper or lower extremity weakness or
arrhythmias at his age. What are the baseline percentage chances of inheritance for
their offspring?
A. Non-carriers 50%, Carrier 25%, Affected 25%
B. Non-carriers 25%, Carrier 50%, Affected 25%
C. Non-carriers 25%, Carrier 25%, Affected 25%
D. Affected 50%, Non-affected 25%
CORRECT ANSWER: A
RATIONALE: X-linked recessive disorders are caused by a mutation on the X
chromosome. The mother is a carrier (
XMXcap X to the cap M-th power cap X
𝑋𝑀𝑋
) and the father is unaffected (
XYcap X to the cap Y-th power
𝑋𝑌
,). Crossing these genotypes yields four possibilities: healthy female non-carrier
(XX), carrier female (
XMXcap X to the cap M-th power cap X
𝑋𝑀𝑋
), healthy male (XY), and affected male (
XMYcap X to the cap M-th power cap Y
𝑋𝑀𝑌
). Combining the two healthy categories (female non-carrier and healthy male)
results in a 50% chance of non-carrier offspring. There is a 25% chance of a
carrier female and a 25% chance of an affected male.
Question 2
If two heterozygous individuals (Aa × Aa) mated and their first three children
consecutively expressed the phenotype for an autosomal dominant trait, which of
the following statements is true regarding their fourth child?
A. The next child will definitely express the dominant trait.
B. The next child will definitely express the recessive trait.
C. There is a 25% chance their next child will show the recessive trait.
D. They cannot conceive a child with the recessive trait.
CORRECT ANSWER: C
RATIONALE: Mendelian genetic events are entirely independent, meaning
previous offspring outcomes do not influence future probabilities. When two
heterozygous individuals for a dominant trait mate, a standard Punnett square
reveals a 75% chance (AA or Aa) of the offspring expressing the dominant
phenotype and a 25% chance (aa) of expressing the homozygous recessive
trait.
,Question 3
In an autosomal dominant disorder, the mother is affected (heterozygous) and
the father is completely unaffected. What is the calculated risk profile for their
offspring?
A. Affected 50%, Unaffected 50%
B. Affected 25%, Unaffected 75%
C. Affected 75%, Unaffected 25%
D. Affected 100%, Unaffected 0%
CORRECT ANSWER: A
RATIONALE: An autosomal dominant trait is expressed when only one copy
of the mutated allele is inherited. Crossing an affected heterozygous mother (Aa)
with an unaffected father (aa) yields a 50% chance of heterozygous affected
offspring (Aa) and a 50% chance of homozygous unaffected offspring (aa).
Question 4
In an autosomal recessive disorder, the mother is a non-carrier and the father is
clinically affected. What is the expected inheritance distribution for their children?
A. Carrier 25%, Non-carrier 75%, Affected 0%
B. Carrier 25%, Non-carrier 25%, Affected 50%
C. Carrier 100%, Affected 0%
D. Carrier 75%, Non-carrier 25%, Affected 0%
CORRECT ANSWER: C
RATIONALE: For an autosomal recessive phenotype to be expressed, the
offspring must inherit two copies of the abnormal gene. Crossing a non-carrier
mother (AA) with an affected father (aa) means the father will contribute a mutated
allele (a) to every child, while the mother will contribute a healthy allele (A). As a
result, 100% of the offspring will be obligate asymptomatic carriers (Aa) and
0% will be affected (aa).
Question 5
In an autosomal recessive disorder, the mother is an asymptomatic carrier and the
father is clinically affected. What is the probability distribution for their offspring?
, A. Carrier 25%, Non-carrier 75%, Affected 0%
B. Carrier 25%, Non-carrier 25%, Affected 50%
C. Carrier 25%, Affected 75%
D. Carrier 50%, Affected 50%
CORRECT ANSWER: D
RATIONALE: Crossing an asymptomatic carrier mother (Aa) with a
homozygous affected father (aa) yields two genotypes: 50% heterozygous carriers
(Aa) and 50% homozygous affected individuals (aa). None of the offspring can
be non-carriers because the father can only pass on a mutated allele.
Question 6
In an X-linked dominant disorder, the mother is affected (heterozygous) and the
father is unaffected. What is the inheritance chance for their offspring?
A. Carrier 25%, Non-carrier 75%, Affected 0%
B. Affected 50%, Non-affected 50%
C. Affected 75%, Non-affected 25%
D. None of the above options are correct
CORRECT ANSWER: B
RATIONALE: An X-linked dominant disorder is caused by a mutation on the X
chromosome and expresses its phenotype in both males and females who inherit
the mutated chromosome. Crossing an affected heterozygous mother (
XMXcap X to the cap M-th power cap X
𝑋𝑀𝑋
) with an unaffected father (
XYcap X to the cap Y-th power
𝑋𝑌
) yields a 50% chance of affected offspring (regardless of sex, inheriting