Oregon Genetic Counselor Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. Which principle is fundamental to the practice of genetic counseling?
A. Providing only laboratory test results without interpretation
B. Helping individuals understand genetic information and its implications
for medical and personal decision-making
C. Recommending a single reproductive decision for every patient
D. Restricting counseling to patients with confirmed genetic disorders
Rationale: Genetic counseling helps individuals understand genetic
information, including inheritance, testing options, medical implications,
and psychosocial considerations, so they can make informed decisions.
2. Which inheritance pattern is characterized by affected individuals
appearing in successive generations and transmission from an affected
parent to approximately half of offspring?
A. Autosomal recessive
B. X-linked recessive
C. Autosomal dominant
D. Mitochondrial only
,Rationale: Autosomal dominant disorders commonly occur in successive
generations, and an affected heterozygous parent has a 50% chance of
transmitting the pathogenic variant to each child.
3. Two unaffected parents have a child with an autosomal recessive
disorder. What is the probability that each subsequent pregnancy will
be affected, assuming both parents are confirmed heterozygous
carriers?
A. 0%
B. 25%
C. 25%
D. 50%
Rationale: When both parents are heterozygous carriers of an autosomal
recessive condition, each pregnancy has a 25% probability of producing an
affected child.
4. If both parents are heterozygous carriers for an autosomal recessive
disorder, what is the probability that their child will be an unaffected
carrier?
A. 0%
B. 50%
C. 75%
D. 100%
Rationale: A carrier-by-carrier cross produces 25% affected, 50%
unaffected carriers, and 25% unaffected noncarriers in each pregnancy.
5. Which inheritance pattern is most consistent with transmission of a
pathogenic mitochondrial DNA variant from an affected mother to all
of her children?
A. Y-linked inheritance
B. Autosomal dominant inheritance
,C. Maternal mitochondrial inheritance
D. X-linked recessive inheritance
Rationale: Mitochondrial DNA is transmitted primarily through the
maternal lineage, so affected mothers can transmit mitochondrial variants
to their offspring.
6. Which characteristic distinguishes X-linked recessive inheritance from
autosomal recessive inheritance?
A. Females are always affected
B. Males may be affected more frequently because they have only one X
chromosome
C. Fathers transmit their X chromosome to all sons
D. Male-to-male transmission is obligatory
Rationale: Males have one X chromosome, so a pathogenic variant in an X-
linked recessive gene can cause disease without a second pathogenic
allele.
7. A man with an X-linked condition has children with an unaffected
woman who is not a carrier. Which statement is generally correct?
A. All sons will inherit the condition from their father
B. All daughters will inherit the father's X chromosome carrying the
pathogenic variant
C. Half of the sons will inherit the father's X chromosome
D. None of the daughters inherit the father's X chromosome
Rationale: Fathers transmit their X chromosome to all daughters and their
Y chromosome to all sons. Therefore, an affected father transmits an X-
linked pathogenic variant to all daughters in this scenario.
8. Which term describes the proportion of individuals with a particular
pathogenic genotype who actually express the associated phenotype?
, A. Variable expressivity
B. Penetrance
C. Heteroplasmy
D. Anticipation
Rationale: Penetrance refers to the proportion of individuals with a
particular genotype who manifest the associated phenotype.
9. Which term describes differences in severity or clinical features among
individuals who have the same pathogenic variant?
A. Penetrance
B. Variable expressivity
C. Recombination
D. Nondisjunction
Rationale: Variable expressivity means that individuals with the same
genetic condition may demonstrate different degrees or manifestations of
the phenotype.
10. Which genetic mechanism involves failure of homologous
chromosomes or sister chromatids to separate properly during cell
division?
A. Translocation
B. Nondisjunction
C. Inversion
D. Duplication
Rationale: Nondisjunction occurs when chromosomes or chromatids fail to
separate normally, potentially producing cells with abnormal chromosome
numbers.
11. Which chromosomal abnormality involves an extra copy of
chromosome 21?
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. Which principle is fundamental to the practice of genetic counseling?
A. Providing only laboratory test results without interpretation
B. Helping individuals understand genetic information and its implications
for medical and personal decision-making
C. Recommending a single reproductive decision for every patient
D. Restricting counseling to patients with confirmed genetic disorders
Rationale: Genetic counseling helps individuals understand genetic
information, including inheritance, testing options, medical implications,
and psychosocial considerations, so they can make informed decisions.
2. Which inheritance pattern is characterized by affected individuals
appearing in successive generations and transmission from an affected
parent to approximately half of offspring?
A. Autosomal recessive
B. X-linked recessive
C. Autosomal dominant
D. Mitochondrial only
,Rationale: Autosomal dominant disorders commonly occur in successive
generations, and an affected heterozygous parent has a 50% chance of
transmitting the pathogenic variant to each child.
3. Two unaffected parents have a child with an autosomal recessive
disorder. What is the probability that each subsequent pregnancy will
be affected, assuming both parents are confirmed heterozygous
carriers?
A. 0%
B. 25%
C. 25%
D. 50%
Rationale: When both parents are heterozygous carriers of an autosomal
recessive condition, each pregnancy has a 25% probability of producing an
affected child.
4. If both parents are heterozygous carriers for an autosomal recessive
disorder, what is the probability that their child will be an unaffected
carrier?
A. 0%
B. 50%
C. 75%
D. 100%
Rationale: A carrier-by-carrier cross produces 25% affected, 50%
unaffected carriers, and 25% unaffected noncarriers in each pregnancy.
5. Which inheritance pattern is most consistent with transmission of a
pathogenic mitochondrial DNA variant from an affected mother to all
of her children?
A. Y-linked inheritance
B. Autosomal dominant inheritance
,C. Maternal mitochondrial inheritance
D. X-linked recessive inheritance
Rationale: Mitochondrial DNA is transmitted primarily through the
maternal lineage, so affected mothers can transmit mitochondrial variants
to their offspring.
6. Which characteristic distinguishes X-linked recessive inheritance from
autosomal recessive inheritance?
A. Females are always affected
B. Males may be affected more frequently because they have only one X
chromosome
C. Fathers transmit their X chromosome to all sons
D. Male-to-male transmission is obligatory
Rationale: Males have one X chromosome, so a pathogenic variant in an X-
linked recessive gene can cause disease without a second pathogenic
allele.
7. A man with an X-linked condition has children with an unaffected
woman who is not a carrier. Which statement is generally correct?
A. All sons will inherit the condition from their father
B. All daughters will inherit the father's X chromosome carrying the
pathogenic variant
C. Half of the sons will inherit the father's X chromosome
D. None of the daughters inherit the father's X chromosome
Rationale: Fathers transmit their X chromosome to all daughters and their
Y chromosome to all sons. Therefore, an affected father transmits an X-
linked pathogenic variant to all daughters in this scenario.
8. Which term describes the proportion of individuals with a particular
pathogenic genotype who actually express the associated phenotype?
, A. Variable expressivity
B. Penetrance
C. Heteroplasmy
D. Anticipation
Rationale: Penetrance refers to the proportion of individuals with a
particular genotype who manifest the associated phenotype.
9. Which term describes differences in severity or clinical features among
individuals who have the same pathogenic variant?
A. Penetrance
B. Variable expressivity
C. Recombination
D. Nondisjunction
Rationale: Variable expressivity means that individuals with the same
genetic condition may demonstrate different degrees or manifestations of
the phenotype.
10. Which genetic mechanism involves failure of homologous
chromosomes or sister chromatids to separate properly during cell
division?
A. Translocation
B. Nondisjunction
C. Inversion
D. Duplication
Rationale: Nondisjunction occurs when chromosomes or chromatids fail to
separate normally, potentially producing cells with abnormal chromosome
numbers.
11. Which chromosomal abnormality involves an extra copy of
chromosome 21?
