PCB 3063 Exam 1 V1 | PCB 3063 Genetics
| Actual Q&A with Rationale (PCB3063
Exam 1) | University of Central Florida
1. During which phase of the cell cycle does DNA replication occur to ensure each daughter
cell receives a full genome?
A. G1 phase
B. G2 phase
C. S phase
D. M phase
Answer: C
Rationale: The S phase, or synthesis phase, is specifically designated for the replication of
the cell’s genetic material. This phase follows the G1 phase where the cell grows and
prepares for DNA synthesis. Successful completion of the S phase results in chromosomes
consisting of two identical sister chromatids.
2. What is the expected phenotypic ratio of a dihybrid cross between two individuals that are
heterozygous for both traits, assuming independent assortment?
A. 9:3:3:1
B. 1:2:1
C. 3:1
,D. 1:1:1:1
Answer: A
Rationale: A 9:3:3:1 ratio is the classic Mendelian result for a dihybrid cross involving two
heterozygous parents. This ratio represents the four possible phenotypic combinations:
dominant-dominant, dominant-recessive, recessive-dominant, and recessive-recessive. It
assumes that the genes are located on different chromosomes and exhibit simple
dominance.
3. In a pedigree analysis, a shaded square traditionally represents which of the following
individuals?
A. Affected male
B. Affected female
C. Unaffected male
D. Unaffected female
Answer: A
Rationale: In standard pedigree nomenclature, squares denote males and circles denote
females. Shading an individual indicates that they express the trait or condition being
tracked. Therefore, a shaded square represents a male who possesses the phenotype under
study.
, 4. Which law states that the two alleles for a heritable character segregate during gamete
formation and end up in different gametes?
A. Law of Segregation
B. Law of Independent Assortment
C. Law of Dominance
D. Law of Recombination
Answer: A
Rationale: Mendel’s Law of Segregation describes the behavior of alleles for a single gene
during meiosis. This ensures that each gamete carries only one allele for each gene. The
physical basis for this law is the separation of homologous chromosomes during Anaphase
I of meiosis.
5. What is the chromosomal composition of an individual with Turner Syndrome?
A. 47, XXY
B. 47, XXX
C. 45, X
D. 45, Y
Answer: C
Rationale: Turner Syndrome is a form of aneuploidy characterized by the presence of only
one X chromosome. Affected individuals are phenotypically female but typically exhibit
| Actual Q&A with Rationale (PCB3063
Exam 1) | University of Central Florida
1. During which phase of the cell cycle does DNA replication occur to ensure each daughter
cell receives a full genome?
A. G1 phase
B. G2 phase
C. S phase
D. M phase
Answer: C
Rationale: The S phase, or synthesis phase, is specifically designated for the replication of
the cell’s genetic material. This phase follows the G1 phase where the cell grows and
prepares for DNA synthesis. Successful completion of the S phase results in chromosomes
consisting of two identical sister chromatids.
2. What is the expected phenotypic ratio of a dihybrid cross between two individuals that are
heterozygous for both traits, assuming independent assortment?
A. 9:3:3:1
B. 1:2:1
C. 3:1
,D. 1:1:1:1
Answer: A
Rationale: A 9:3:3:1 ratio is the classic Mendelian result for a dihybrid cross involving two
heterozygous parents. This ratio represents the four possible phenotypic combinations:
dominant-dominant, dominant-recessive, recessive-dominant, and recessive-recessive. It
assumes that the genes are located on different chromosomes and exhibit simple
dominance.
3. In a pedigree analysis, a shaded square traditionally represents which of the following
individuals?
A. Affected male
B. Affected female
C. Unaffected male
D. Unaffected female
Answer: A
Rationale: In standard pedigree nomenclature, squares denote males and circles denote
females. Shading an individual indicates that they express the trait or condition being
tracked. Therefore, a shaded square represents a male who possesses the phenotype under
study.
, 4. Which law states that the two alleles for a heritable character segregate during gamete
formation and end up in different gametes?
A. Law of Segregation
B. Law of Independent Assortment
C. Law of Dominance
D. Law of Recombination
Answer: A
Rationale: Mendel’s Law of Segregation describes the behavior of alleles for a single gene
during meiosis. This ensures that each gamete carries only one allele for each gene. The
physical basis for this law is the separation of homologous chromosomes during Anaphase
I of meiosis.
5. What is the chromosomal composition of an individual with Turner Syndrome?
A. 47, XXY
B. 47, XXX
C. 45, X
D. 45, Y
Answer: C
Rationale: Turner Syndrome is a form of aneuploidy characterized by the presence of only
one X chromosome. Affected individuals are phenotypically female but typically exhibit
