PCB 3063 Final Exam V1 | PCB 3063
Genetics | Actual Q&A with Rationale
(PCB3063 Final Exam) | University of
Central Florida
1. According to Mendel’s Principle of Segregation, what happens to the two alleles for a trait
during gamete formation?
A. They replicate to ensure each gamete gets two copies.
B. They separate so that each gamete receives only one allele.
C. They fuse together to create a new hybrid allele.
D. They are randomly destroyed to maintain the haploid number.
Answer: B
Rationale: Mendel’s First Law states that allele pairs separate or segregate during gamete
formation. This means that a parent passes on only one allele for each gene to its offspring.
This process is physically represented by the separation of homologous chromosomes
during Anaphase I of meiosis.
2. In a dihybrid cross between two individuals heterozygous for two independently assorting
genes (AaBb x AaBb), what is the expected phenotypic ratio?
A. 1:1:1:1
B. 9:3:3:1
,C. 3:1
D. 1:2:1
Answer: B
Rationale: The 9:3:3:1 ratio is the classic Mendelian ratio for a dihybrid cross involving
independent assortment. This ratio assumes that both genes exhibit complete dominance
and do not interact epistatically. Each phenotypic class represents the combination of the
individual 3:1 ratios for each gene (3/4 * 3/4 = 9/16, etc.).
3. Which of the following describes a testcross?
A. Crossing a heterozygous individual with a homozygous dominant individual.
B. Crossing two individuals that are both homozygous dominant.
C. Crossing an individual of unknown genotype with a homozygous recessive individual.
D. Crossing two individuals from the F2 generation together.
Answer: C
Rationale: A testcross is used to determine whether an individual with a dominant
phenotype is homozygous or heterozygous. By using a homozygous recessive mate, the
researcher ensures that the mate contributes only recessive alleles. The resulting offspring
phenotypes directly reveal the genotype of the unknown parent.
, 4. If a child has blood type O and the mother has blood type A, which of the following could
NOT be the father’s blood type?
A. Type O
B. Type AB
C. Type B
D. Type A
Answer: B
Rationale: Type O blood is recessive and requires two ‘i’ alleles, meaning the child is
genotype ii. Since the mother is Type A, she must be genotype Ai to provide one ‘i’ allele. An
individual with Type AB blood has the genotype AB and cannot contribute an ‘i’ allele,
making them an impossible biological parent for a Type O child.
5. Which molecular bond connects the sugar-phosphate backbone of a single DNA strand?
A. Hydrogen bond
B. Peptide bond
C. Ionic bond
D. Phosphodiester bond
Answer: D
Rationale: The backbone of DNA consists of alternating sugar and phosphate groups
linked by covalent phosphodiester bonds. These bonds form between the 3’ carbon atom of
Genetics | Actual Q&A with Rationale
(PCB3063 Final Exam) | University of
Central Florida
1. According to Mendel’s Principle of Segregation, what happens to the two alleles for a trait
during gamete formation?
A. They replicate to ensure each gamete gets two copies.
B. They separate so that each gamete receives only one allele.
C. They fuse together to create a new hybrid allele.
D. They are randomly destroyed to maintain the haploid number.
Answer: B
Rationale: Mendel’s First Law states that allele pairs separate or segregate during gamete
formation. This means that a parent passes on only one allele for each gene to its offspring.
This process is physically represented by the separation of homologous chromosomes
during Anaphase I of meiosis.
2. In a dihybrid cross between two individuals heterozygous for two independently assorting
genes (AaBb x AaBb), what is the expected phenotypic ratio?
A. 1:1:1:1
B. 9:3:3:1
,C. 3:1
D. 1:2:1
Answer: B
Rationale: The 9:3:3:1 ratio is the classic Mendelian ratio for a dihybrid cross involving
independent assortment. This ratio assumes that both genes exhibit complete dominance
and do not interact epistatically. Each phenotypic class represents the combination of the
individual 3:1 ratios for each gene (3/4 * 3/4 = 9/16, etc.).
3. Which of the following describes a testcross?
A. Crossing a heterozygous individual with a homozygous dominant individual.
B. Crossing two individuals that are both homozygous dominant.
C. Crossing an individual of unknown genotype with a homozygous recessive individual.
D. Crossing two individuals from the F2 generation together.
Answer: C
Rationale: A testcross is used to determine whether an individual with a dominant
phenotype is homozygous or heterozygous. By using a homozygous recessive mate, the
researcher ensures that the mate contributes only recessive alleles. The resulting offspring
phenotypes directly reveal the genotype of the unknown parent.
, 4. If a child has blood type O and the mother has blood type A, which of the following could
NOT be the father’s blood type?
A. Type O
B. Type AB
C. Type B
D. Type A
Answer: B
Rationale: Type O blood is recessive and requires two ‘i’ alleles, meaning the child is
genotype ii. Since the mother is Type A, she must be genotype Ai to provide one ‘i’ allele. An
individual with Type AB blood has the genotype AB and cannot contribute an ‘i’ allele,
making them an impossible biological parent for a Type O child.
5. Which molecular bond connects the sugar-phosphate backbone of a single DNA strand?
A. Hydrogen bond
B. Peptide bond
C. Ionic bond
D. Phosphodiester bond
Answer: D
Rationale: The backbone of DNA consists of alternating sugar and phosphate groups
linked by covalent phosphodiester bonds. These bonds form between the 3’ carbon atom of
