Bio 337 Final Exam QUESTIONS
AND CORRECT ANSWERS <
RECENT VERSION 2025/2026 >
SURE TO PASS!!
1. A 30-year-old woman had a sister who died from
infantile Tay-Sachs disease, an autosomal recessive
disorder that is fatal by age 5 years. What is the
probability that this woman is a heterozygous carrier? -
ANSWER ✓ 2/3
2. The pedigree to the right shows inheritance of
hemophilia A, an X-linked recessive disorder. What is
the probability that the male in generation IV is
affected? - ANSWER ✓ 1/2
3. A female carrier of an X-linked recessive condition
marries a phenotypically normal man. What is the
probability (risk) that their first son will be affected? -
ANSWER ✓ 1/2
,4. Some genes influence multiple, and apparently
unrelated traits. The genetic effect these genes caused is
known as - ANSWER ✓ pleiotropy
5. Penetrance - ANSWER ✓ The percentage of
individuals with a particular genotype that actually
displays the phenotype associated with the genotype.
6. New Mutation - ANSWER ✓ when no history of an
autosomal dominant condition is present, but child
develops the mutation
7. Incomplete Dominance - ANSWER ✓ Situation in
which one allele is not completely dominant over
another allele
8. Homologous chromosomes pair and exchange segments
(cross over) during: - ANSWER ✓ Prophase I of
meiosis
9. Most children with cystic fibrosis have frequent lung
infections and digestive difficulties. Some have mild
, cases, with onset of minor respiratory problems in
adulthood. Some men have cystic fibrosis, but their
only symptom is infertility. - ANSWER ✓ Variable
Expression
10. Variable Expression - ANSWER ✓ Refers to the
range of signs and symptoms that can occur in different
people with the same genetic condition.
11. Two parents are heterozygous for genes that cause
albinism, but each gene specifies a different enzyme in
the biochemical pathway for skin pigment synthesis.
Their children thus don't face a 25% risk of having
albinism. - ANSWER ✓ Locus Heterogeneity
12. Late-onset cardiac amyloidosis causes heart failure.
The gene was sequenced, and in some families, found
to be mutated in a few individuals who have healthy
hearts. - ANSWER ✓ Incomplete Penetrance
, 13. Incomplete Penetrance - ANSWER ✓ Not all
individuals with a mutant genotype show the mutant
phenotype
14. Barth syndrome, severe X-linked cardiomyopathy,
and X-linked endocardial fibroelastosis were thought to
be distinct, because of differing degrees of damage to
heart muscle, until gene sequencing revealed that they
result from mutations in the same gene. - ANSWER ✓
Allelic Heterogeneity
15. Data from the US National Huntington's Disease
Roster have been analyzed in terms of the difference in
age of onset (AO) between affected parents and
affected offspring (Journal of Medical Genetics 25:
589-595). While mean AO in offspring of affected
mothers did not differ greatly from AO in their mothers,
the distribution of AO in the offspring of affected
fathers falls into two groups, and in one of the two
groups, AO was 24 years younger than their affected
fathers. - ANSWER ✓ Anticipation
AND CORRECT ANSWERS <
RECENT VERSION 2025/2026 >
SURE TO PASS!!
1. A 30-year-old woman had a sister who died from
infantile Tay-Sachs disease, an autosomal recessive
disorder that is fatal by age 5 years. What is the
probability that this woman is a heterozygous carrier? -
ANSWER ✓ 2/3
2. The pedigree to the right shows inheritance of
hemophilia A, an X-linked recessive disorder. What is
the probability that the male in generation IV is
affected? - ANSWER ✓ 1/2
3. A female carrier of an X-linked recessive condition
marries a phenotypically normal man. What is the
probability (risk) that their first son will be affected? -
ANSWER ✓ 1/2
,4. Some genes influence multiple, and apparently
unrelated traits. The genetic effect these genes caused is
known as - ANSWER ✓ pleiotropy
5. Penetrance - ANSWER ✓ The percentage of
individuals with a particular genotype that actually
displays the phenotype associated with the genotype.
6. New Mutation - ANSWER ✓ when no history of an
autosomal dominant condition is present, but child
develops the mutation
7. Incomplete Dominance - ANSWER ✓ Situation in
which one allele is not completely dominant over
another allele
8. Homologous chromosomes pair and exchange segments
(cross over) during: - ANSWER ✓ Prophase I of
meiosis
9. Most children with cystic fibrosis have frequent lung
infections and digestive difficulties. Some have mild
, cases, with onset of minor respiratory problems in
adulthood. Some men have cystic fibrosis, but their
only symptom is infertility. - ANSWER ✓ Variable
Expression
10. Variable Expression - ANSWER ✓ Refers to the
range of signs and symptoms that can occur in different
people with the same genetic condition.
11. Two parents are heterozygous for genes that cause
albinism, but each gene specifies a different enzyme in
the biochemical pathway for skin pigment synthesis.
Their children thus don't face a 25% risk of having
albinism. - ANSWER ✓ Locus Heterogeneity
12. Late-onset cardiac amyloidosis causes heart failure.
The gene was sequenced, and in some families, found
to be mutated in a few individuals who have healthy
hearts. - ANSWER ✓ Incomplete Penetrance
, 13. Incomplete Penetrance - ANSWER ✓ Not all
individuals with a mutant genotype show the mutant
phenotype
14. Barth syndrome, severe X-linked cardiomyopathy,
and X-linked endocardial fibroelastosis were thought to
be distinct, because of differing degrees of damage to
heart muscle, until gene sequencing revealed that they
result from mutations in the same gene. - ANSWER ✓
Allelic Heterogeneity
15. Data from the US National Huntington's Disease
Roster have been analyzed in terms of the difference in
age of onset (AO) between affected parents and
affected offspring (Journal of Medical Genetics 25:
589-595). While mean AO in offspring of affected
mothers did not differ greatly from AO in their mothers,
the distribution of AO in the offspring of affected
fathers falls into two groups, and in one of the two
groups, AO was 24 years younger than their affected
fathers. - ANSWER ✓ Anticipation
