NU 318 – Nursing Genetics EXAM 2026-2027 LATEST
UPDATED VERSION QUESTIONS AND ANSWERS
Is it possible for two parents with achondroplasia to have a child who is of normal stature?
A.
Yes, because the disorder is autosomal dominant, and if both parents are heterozygous, the child could
inherit two normal stature gene alleles.
B.
Yes, if the parent who is homozygous for the gene mutation demonstrates variable expressivity of the
health problem.
C.
No, because the disorder is autosomal recessive, and the child can only inherit two mutated gene alleles
for the health problem.
D.
No, because homozygosity for this health problem is lethal. - answer>>A. Yes, because the disorder is
autosomal dominant, and if both parents are heterozygous, the child could inherit two normal stature
gene alleles.
Achondroplasia is an autosomal-dominant trait that is lethal when the genotype is homozygous. Thus,
both parents must be heterozygous A/n (with an A allele for achondroplasia and an n allele for normal
stature). Normal stature (n allele) is recessive. Thus, for a child to have a normal-stature phenotype
from these two parents, her or her genotype would have to be n/n. As shown by the Punnett square,
the chances for this couple to have a child with normal stature is 25% with each pregnancy.
What is the risk for a person to inherit an autosomal-dominant genetic disease-causing allele from a
parent who is heterozygous if the disorder has a penetrance factor of 75%?
A.
100%
B.
75%
C.
,50%
D.
25% - answer>>C. 50%
The risk for inheriting an autosomal-dominant allele from a parent who has the allele is always 50%. The
inheritance risk is not changed by penetrance, but expression can be.
Which statement reflects the criterion for autosomal-dominant transmission of single-gene traits?
A.
The risk for a person who is homozygous for the trait to transmit the trait to his or her children is 100%
with each pregnancy.
B.
The trait often remains unexpressed within a kindred for many generations until a change in
environment promotes its expression.
C.
Males in a kindred are more likely to express the trait when the mother has the trait, and females in a
kindred are more likely to express the trait when the father has the trait.
D.
Females in a kindred are more likely to express the trait when the mother has the trait, and males in a
kindred are more likely to express the trait when the father has the trait. - answer>>A. The risk for a
person who is homozygous for the trait to transmit the trait to his or her children is 100% with each
pregnancy
With homozygosity of the autosomal-dominant trait, the parent only has a dominant allele to transmit.
Therefore, any child this person produces will have received the trait allele and is likely to express it.
Dominant traits are usually expressed and do not remain unexpressed from one generation to another.
For autosomal-dominant transmission, the genders of the parent and of the child are unimportant. Both
males and females transmit the allele equally to sons and daughters.
In which situation are phenotype and genotype always the same?
A.
X-linked-recessive traits
,B.
X-linked-dominant traits
C.
Autosomal-recessive traits
D.
Autosomal-dominant traits - answer>>C. Autosomal-recessive traits
Autosomal-recessive traits are only expressed in the homozygous state in which the genotype matches
the phenotype. Autosomal-dominant traits can be expressed in either the homozygous or the
heterozygous state. Thus, with autosomal-dominant expression, phenotype and genotype do not have
to match. In X-linked-recessive traits, males express the trait in a dominant manner. In X-linked-
dominant traits, females express the trait in either the homozygous or heterozygous state.
A girl of normal stature is born to two parents with achondroplasia who have very short stature,
especially disproportionately short arms and legs. What is the probability (by Punnett square analysis)
that any pregnancy this girl eventually has will result in the birth of an infant with achondroplasia if her
partner also has normal stature?
A.
Three out of four (75%)
B.
Two out of four (50%)
C.
One out of four (25%)
D.
Zero out of four (0%) - answer>>D. Zero out of four (0%)
Achondroplasia is an autosomal-dominant trait that is lethal when the genotype is homozygous. Thus,
both parents must be heterozygous A/n (with an A allele for achondroplasia and an n allele for normal
stature). Normal stature (n allele) is recessive. Thus, for the child to have a normal-stature phenotype
from these two parents, her genotype is n/n. Because she does not have an A allele as her genotype,
she can only transmit an n allele. The Punnett square would show:
, Which statement or factor is a criterion for autosomal-recessive transmission of single-gene traits?
A.
About 25% of the members of a large kindred with an autosomal-recessive trait will express the trait.
B.
There is no carrier status; if the allele for the trait is present, it is expressed, although the degree of
expression can be variable.
C.
Individuals who are heterozygous for an autosomal-recessive trait have minimal risk for transmitting the
allele to their offspring.
D.
The degree of expression of an autosomal-recessive trait or disorder in a homozygous individual is
directly related to the penetrance of the trait. - answer>>A. About 25% of the members of a large
kindred with an autosomal-recessive trait will express the trait.
Because autosomal-recessive traits or disorders are only expressed in the homozygous state, expression
of the trait or disorder within a large kindred remains at a relatively constant level of no greater than
about 25%. The heterozygous individual is a carrier who has a 50% chance with each pregnancy of
transmitting the allele to his or her offspring. There is no evidence to support the presence of the
concept of "penetrance" in autosomal-recessive traits and disorders. This issue appears to be
associated only with dominant traits and disorders.
Which person is an obligate carrier of an autosomal-recessive single-gene trait or disorder without
expressing the trait or disorder?
A.
The son of a man with classic hemophilia
B.
The daughter of a woman with Marfan syndrome
C.
The son of a man who expresses a widow's peak hairline
D.
The daughter of a woman who expresses attached earlobes - answer>>D. The daughter of a woman
who expresses attached earlobes
UPDATED VERSION QUESTIONS AND ANSWERS
Is it possible for two parents with achondroplasia to have a child who is of normal stature?
A.
Yes, because the disorder is autosomal dominant, and if both parents are heterozygous, the child could
inherit two normal stature gene alleles.
B.
Yes, if the parent who is homozygous for the gene mutation demonstrates variable expressivity of the
health problem.
C.
No, because the disorder is autosomal recessive, and the child can only inherit two mutated gene alleles
for the health problem.
D.
No, because homozygosity for this health problem is lethal. - answer>>A. Yes, because the disorder is
autosomal dominant, and if both parents are heterozygous, the child could inherit two normal stature
gene alleles.
Achondroplasia is an autosomal-dominant trait that is lethal when the genotype is homozygous. Thus,
both parents must be heterozygous A/n (with an A allele for achondroplasia and an n allele for normal
stature). Normal stature (n allele) is recessive. Thus, for a child to have a normal-stature phenotype
from these two parents, her or her genotype would have to be n/n. As shown by the Punnett square,
the chances for this couple to have a child with normal stature is 25% with each pregnancy.
What is the risk for a person to inherit an autosomal-dominant genetic disease-causing allele from a
parent who is heterozygous if the disorder has a penetrance factor of 75%?
A.
100%
B.
75%
C.
,50%
D.
25% - answer>>C. 50%
The risk for inheriting an autosomal-dominant allele from a parent who has the allele is always 50%. The
inheritance risk is not changed by penetrance, but expression can be.
Which statement reflects the criterion for autosomal-dominant transmission of single-gene traits?
A.
The risk for a person who is homozygous for the trait to transmit the trait to his or her children is 100%
with each pregnancy.
B.
The trait often remains unexpressed within a kindred for many generations until a change in
environment promotes its expression.
C.
Males in a kindred are more likely to express the trait when the mother has the trait, and females in a
kindred are more likely to express the trait when the father has the trait.
D.
Females in a kindred are more likely to express the trait when the mother has the trait, and males in a
kindred are more likely to express the trait when the father has the trait. - answer>>A. The risk for a
person who is homozygous for the trait to transmit the trait to his or her children is 100% with each
pregnancy
With homozygosity of the autosomal-dominant trait, the parent only has a dominant allele to transmit.
Therefore, any child this person produces will have received the trait allele and is likely to express it.
Dominant traits are usually expressed and do not remain unexpressed from one generation to another.
For autosomal-dominant transmission, the genders of the parent and of the child are unimportant. Both
males and females transmit the allele equally to sons and daughters.
In which situation are phenotype and genotype always the same?
A.
X-linked-recessive traits
,B.
X-linked-dominant traits
C.
Autosomal-recessive traits
D.
Autosomal-dominant traits - answer>>C. Autosomal-recessive traits
Autosomal-recessive traits are only expressed in the homozygous state in which the genotype matches
the phenotype. Autosomal-dominant traits can be expressed in either the homozygous or the
heterozygous state. Thus, with autosomal-dominant expression, phenotype and genotype do not have
to match. In X-linked-recessive traits, males express the trait in a dominant manner. In X-linked-
dominant traits, females express the trait in either the homozygous or heterozygous state.
A girl of normal stature is born to two parents with achondroplasia who have very short stature,
especially disproportionately short arms and legs. What is the probability (by Punnett square analysis)
that any pregnancy this girl eventually has will result in the birth of an infant with achondroplasia if her
partner also has normal stature?
A.
Three out of four (75%)
B.
Two out of four (50%)
C.
One out of four (25%)
D.
Zero out of four (0%) - answer>>D. Zero out of four (0%)
Achondroplasia is an autosomal-dominant trait that is lethal when the genotype is homozygous. Thus,
both parents must be heterozygous A/n (with an A allele for achondroplasia and an n allele for normal
stature). Normal stature (n allele) is recessive. Thus, for the child to have a normal-stature phenotype
from these two parents, her genotype is n/n. Because she does not have an A allele as her genotype,
she can only transmit an n allele. The Punnett square would show:
, Which statement or factor is a criterion for autosomal-recessive transmission of single-gene traits?
A.
About 25% of the members of a large kindred with an autosomal-recessive trait will express the trait.
B.
There is no carrier status; if the allele for the trait is present, it is expressed, although the degree of
expression can be variable.
C.
Individuals who are heterozygous for an autosomal-recessive trait have minimal risk for transmitting the
allele to their offspring.
D.
The degree of expression of an autosomal-recessive trait or disorder in a homozygous individual is
directly related to the penetrance of the trait. - answer>>A. About 25% of the members of a large
kindred with an autosomal-recessive trait will express the trait.
Because autosomal-recessive traits or disorders are only expressed in the homozygous state, expression
of the trait or disorder within a large kindred remains at a relatively constant level of no greater than
about 25%. The heterozygous individual is a carrier who has a 50% chance with each pregnancy of
transmitting the allele to his or her offspring. There is no evidence to support the presence of the
concept of "penetrance" in autosomal-recessive traits and disorders. This issue appears to be
associated only with dominant traits and disorders.
Which person is an obligate carrier of an autosomal-recessive single-gene trait or disorder without
expressing the trait or disorder?
A.
The son of a man with classic hemophilia
B.
The daughter of a woman with Marfan syndrome
C.
The son of a man who expresses a widow's peak hairline
D.
The daughter of a woman who expresses attached earlobes - answer>>D. The daughter of a woman
who expresses attached earlobes
