BIOD 210 Module 5 Exam – Genetics Portage Learning – (2026) Actual Questions
& Answers
Table of Contents
Section Topic Area Questions
A Mendelian Genetics & Inheritance Patterns 1-25
B Linkage, Recombination & Gene Mapping 26-40
C Population Genetics & Hardy-Weinberg Equilibrium 41-55
D DNA Replication & Central Dogma 56-80
E Transcription & RNA Processing81-105
F Translation & The Genetic Code 106-125
G Gene Regulation (Operons & Epigenetics) 126-145
H Mutations & DNA Repair 146-160
I Genetic Technology & Applications 161-175
J Advanced Genetics Concepts 176-200
Section A: Mendelian Genetics & Inheritance Patterns
Question 1
In a dihybrid cross between two individuals heterozygous for two unlinked genes
(AaBb × AaBb), what is the probability of obtaining an offspring with the dominant
phenotype for both traits?
,A) 9/16
B) 3/16
C) 1/16
D) 1/4
Answer: A
Rationale: For each gene, the probability of the dominant phenotype is 3/4. Since
the genes are independent (unlinked), the combined probability is (3/4) × (3/4) =
9/16. This is the classic Mendelian ratio for a dihybrid cross .
Question 2
What is the expected phenotypic ratio from a cross between two individuals that
are both heterozygous for a single gene (Aa × Aa)?
A) 1:1
B) 3:1
C) 9:3:3:1
D) 1:2:1
Answer: B
,Rationale: A monohybrid cross between two heterozygotes yields a 3:1
phenotypic ratio, with three offspring showing the dominant trait for every one
showing the recessive trait. The genotypic ratio is 1:2:1 (AA:Aa:aa).
Question 3
In a pedigree for an autosomal recessive disorder, two unaffected parents have
an affected child. What is the probability that their next child will be a carrier
(unaffected but heterozygous)?
A) 1/4
B) 1/2
C) 2/3
D) 3/4
Answer: B
Rationale: Both unaffected parents must be carriers (Aa) to produce an affected
child (aa). From an Aa × Aa cross, the probability of a child being a carrier (Aa) is
1/2. The probability of being affected is 1/4, and homozygous dominant is 1/4 .
Question 4
, A man with hemophilia (an X-linked recessive disorder) marries a woman who is a
carrier. What is the probability that a son they have will be affected?
A) 1/4
B) 1/2
C) 3/4
D) 1
Answer: B
Rationale: The father passes his Y chromosome to sons, so sons inherit their only
X chromosome from their mother. The mother is a carrier (XᴴXʰ), so there is a 1/2
chance she will pass the Xʰ (hemophilia allele) to any son. All sons who receive Xʰ
will be affected .
Question 5
In a species of plant, flower color is determined by two genes. When both
dominant alleles are present (A_B_), purple color results. AaBb plants are self-
crossed. What is the expected phenotypic ratio?
A) 9 purple : 7 white
B) 9 purple : 3 red : 3 blue : 1 white
& Answers
Table of Contents
Section Topic Area Questions
A Mendelian Genetics & Inheritance Patterns 1-25
B Linkage, Recombination & Gene Mapping 26-40
C Population Genetics & Hardy-Weinberg Equilibrium 41-55
D DNA Replication & Central Dogma 56-80
E Transcription & RNA Processing81-105
F Translation & The Genetic Code 106-125
G Gene Regulation (Operons & Epigenetics) 126-145
H Mutations & DNA Repair 146-160
I Genetic Technology & Applications 161-175
J Advanced Genetics Concepts 176-200
Section A: Mendelian Genetics & Inheritance Patterns
Question 1
In a dihybrid cross between two individuals heterozygous for two unlinked genes
(AaBb × AaBb), what is the probability of obtaining an offspring with the dominant
phenotype for both traits?
,A) 9/16
B) 3/16
C) 1/16
D) 1/4
Answer: A
Rationale: For each gene, the probability of the dominant phenotype is 3/4. Since
the genes are independent (unlinked), the combined probability is (3/4) × (3/4) =
9/16. This is the classic Mendelian ratio for a dihybrid cross .
Question 2
What is the expected phenotypic ratio from a cross between two individuals that
are both heterozygous for a single gene (Aa × Aa)?
A) 1:1
B) 3:1
C) 9:3:3:1
D) 1:2:1
Answer: B
,Rationale: A monohybrid cross between two heterozygotes yields a 3:1
phenotypic ratio, with three offspring showing the dominant trait for every one
showing the recessive trait. The genotypic ratio is 1:2:1 (AA:Aa:aa).
Question 3
In a pedigree for an autosomal recessive disorder, two unaffected parents have
an affected child. What is the probability that their next child will be a carrier
(unaffected but heterozygous)?
A) 1/4
B) 1/2
C) 2/3
D) 3/4
Answer: B
Rationale: Both unaffected parents must be carriers (Aa) to produce an affected
child (aa). From an Aa × Aa cross, the probability of a child being a carrier (Aa) is
1/2. The probability of being affected is 1/4, and homozygous dominant is 1/4 .
Question 4
, A man with hemophilia (an X-linked recessive disorder) marries a woman who is a
carrier. What is the probability that a son they have will be affected?
A) 1/4
B) 1/2
C) 3/4
D) 1
Answer: B
Rationale: The father passes his Y chromosome to sons, so sons inherit their only
X chromosome from their mother. The mother is a carrier (XᴴXʰ), so there is a 1/2
chance she will pass the Xʰ (hemophilia allele) to any son. All sons who receive Xʰ
will be affected .
Question 5
In a species of plant, flower color is determined by two genes. When both
dominant alleles are present (A_B_), purple color results. AaBb plants are self-
crossed. What is the expected phenotypic ratio?
A) 9 purple : 7 white
B) 9 purple : 3 red : 3 blue : 1 white
