BIOD 210 Genetics Module 5 Exam - Mutations and Chromosomal
Disorders 2026/2027 UPDATE
1. Which type of mutation occurs when a single nucleotide is replaced by
another, but the resulting amino acid sequence remains unchanged?
A. Missense mutation
B. Silent mutation
C. Nonsense mutation
D. Frameshift mutation
Answer: B
Rationale: A silent mutation is a point mutation that changes a codon to another codon
that specifies the same amino acid, resulting in no change to the protein.
2. A mutation that changes a codon for an amino acid into a stop codon is
known as a:
A. Silent mutation
B. Neutral mutation
C. Missense mutation
D. Nonsense mutation
Answer: D
Rationale: Nonsense mutations create a premature stop codon, leading to truncated and
often nonfunctional proteins.
,3. What is the primary cause of aneuploidy, such as Trisomy 21?
A. DNA polymerase error
B. Exposure to UV radiation
C. Nondisjunction during meiosis
D. Unequal crossing over
Answer: C
Rationale: Nondisjunction is the failure of homologous chromosomes or sister chromatids
to separate properly during cell division, resulting in daughter cells with abnormal
chromosome numbers.
4. Which chromosomal disorder is characterized by a 45, X karyotype?
A. Klinefelter Syndrome
B. Turner Syndrome
C. Down Syndrome
D. Edwards Syndrome
Answer: B
Rationale: Turner Syndrome involves the complete or partial absence of one X
chromosome in females.
5. A ‘Frameshift’ mutation most likely results from which of the following?
A. A base substitution
B. A transition mutation
C. An inversion of a DNA segment
D. An insertion of one or two nucleotides
Answer: D
Rationale: Insertions or deletions that are not multiples of three alter the reading frame of
the genetic message from that point onward.
, 6. Which condition is also known as Trisomy 18?
A. Patau Syndrome
B. Down Syndrome
C. Cri-du-chat Syndrome
D. Edwards Syndrome
Answer: D
Rationale: Edwards Syndrome is caused by the presence of a third copy of all or part of
chromosome 18.
7. In a Robertsonian translocation, which of the following occurs?
A. Two acrocentric chromosomes fuse at the centromere
B. A segment of a chromosome is reversed end-to-end
C. A segment of a chromosome is lost during division
D. A chromosome segment moves to a non-homologous chromosome
Answer: A
Rationale: Robertsonian translocations involve the fusion of the long arms of two
acrocentric chromosomes, with the loss of the short arms.
8. What is the karyotype notation for a male with Klinefelter Syndrome?
A. 47, XXY
B. 45, X
C. 47, XYY
D. 48, XXXY
Answer: A
Rationale: Klinefelter Syndrome is characterized by at least one extra X chromosome in a
male (47, XXY).
Disorders 2026/2027 UPDATE
1. Which type of mutation occurs when a single nucleotide is replaced by
another, but the resulting amino acid sequence remains unchanged?
A. Missense mutation
B. Silent mutation
C. Nonsense mutation
D. Frameshift mutation
Answer: B
Rationale: A silent mutation is a point mutation that changes a codon to another codon
that specifies the same amino acid, resulting in no change to the protein.
2. A mutation that changes a codon for an amino acid into a stop codon is
known as a:
A. Silent mutation
B. Neutral mutation
C. Missense mutation
D. Nonsense mutation
Answer: D
Rationale: Nonsense mutations create a premature stop codon, leading to truncated and
often nonfunctional proteins.
,3. What is the primary cause of aneuploidy, such as Trisomy 21?
A. DNA polymerase error
B. Exposure to UV radiation
C. Nondisjunction during meiosis
D. Unequal crossing over
Answer: C
Rationale: Nondisjunction is the failure of homologous chromosomes or sister chromatids
to separate properly during cell division, resulting in daughter cells with abnormal
chromosome numbers.
4. Which chromosomal disorder is characterized by a 45, X karyotype?
A. Klinefelter Syndrome
B. Turner Syndrome
C. Down Syndrome
D. Edwards Syndrome
Answer: B
Rationale: Turner Syndrome involves the complete or partial absence of one X
chromosome in females.
5. A ‘Frameshift’ mutation most likely results from which of the following?
A. A base substitution
B. A transition mutation
C. An inversion of a DNA segment
D. An insertion of one or two nucleotides
Answer: D
Rationale: Insertions or deletions that are not multiples of three alter the reading frame of
the genetic message from that point onward.
, 6. Which condition is also known as Trisomy 18?
A. Patau Syndrome
B. Down Syndrome
C. Cri-du-chat Syndrome
D. Edwards Syndrome
Answer: D
Rationale: Edwards Syndrome is caused by the presence of a third copy of all or part of
chromosome 18.
7. In a Robertsonian translocation, which of the following occurs?
A. Two acrocentric chromosomes fuse at the centromere
B. A segment of a chromosome is reversed end-to-end
C. A segment of a chromosome is lost during division
D. A chromosome segment moves to a non-homologous chromosome
Answer: A
Rationale: Robertsonian translocations involve the fusion of the long arms of two
acrocentric chromosomes, with the loss of the short arms.
8. What is the karyotype notation for a male with Klinefelter Syndrome?
A. 47, XXY
B. 45, X
C. 47, XYY
D. 48, XXXY
Answer: A
Rationale: Klinefelter Syndrome is characterized by at least one extra X chromosome in a
male (47, XXY).
