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MOLECULAR DIAGNOSTICS (4TH EDITION) EXAM QUESTIONS AND
CORRECT ANSWERS LATEST EDITION 2026
Molecular Diagnostics (4th Edition) – Complete Test Bank & Exam Practice Questions
Chapter 1 — Fundamentals of Molecular Biology
1. A medical technologist is explaining the central dogma of molecular biology to a new
laboratory trainee. According to the textbook's foundational concepts, which of the following
best describes the flow of genetic information in a eukaryotic cell?
A) Protein → RNA → DNA
B) DNA → Protein → RNA
C) DNA → RNA → Protein
D) RNA → DNA → Protein
Answer: C
Rationale: The central dogma of molecular biology describes the flow of genetic information as
DNA being transcribed into RNA, which is then translated into protein. This process involves
transcription (DNA to mRNA) and translation (mRNA to protein). Retroviruses are an exception,
using reverse transcriptase to convert RNA to DNA .
2. A researcher is analyzing a DNA sequence and needs to identify the directionality of the
strand. The 5' carbon connects to which functional group on the adjacent nucleotide?
A) The 1' carbon
B) The 3' hydroxyl group
C) The 5' phosphate group
D) The nitrogenous base
Answer: B
Rationale: The 5' carbon of one nucleotide connects to the hydroxyl group on the 3' ribose
carbon of the previous nucleotide through a phosphodiester bond .
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3. A laboratory scientist is studying RNA function and notes that ribosomal RNA (rRNA)
comprises what percentage of cellular RNA?
A) 10-20%
B) 30-40%
C) 50-60%
D) 80-90%
Answer: D
Rationale: Ribosomal RNA (rRNA) makes up 80-90% of cellular RNA and serves as an important
structural and functional component of ribosomes, which synthesize proteins. In prokaryotes,
the small subunit contains 16S rRNA, while the large subunit contains 23S and 5S rRNA .
4. During mRNA processing, which of the following modifications occurs at the 5' end?
A) Polyadenylation
B) Addition of a modified guanine cap
C) Splicing of exons
D) Addition of a methyl group
Answer: B
Rationale: During mRNA processing, the 5' end of mRNA is capped with a modified guanine
nucleotide. This cap is unique in that it involves a 5'-5' bond, rather than the standard 5'-3' bond
typically found in polynucleotides. Other processing steps include 3' polyadenylation and
splicing .
5. Which RNA polymerase is responsible for synthesizing messenger RNA (mRNA)?
A) RNA polymerase I
B) RNA polymerase II
C) RNA polymerase III
D) RNA polymerase IV
Answer: B
Rationale: In eukaryotic cells, RNA polymerase II synthesizes mRNA, which serves as the genetic
messenger that can be translated into protein. RNA polymerase I synthesizes rRNA, and RNA
polymerase III synthesizes tRNA and other small RNAs .
6. Which of the following is a characteristic of RNA but not DNA?
A) Contains adenine
B) Contains a double helix structure
C) Contains uracil instead of thymine
D) Contains deoxyribose sugar
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Answer: C
Rationale: RNA contains uracil instead of thymine and has a ribose sugar rather than
deoxyribose. Unlike DNA, RNA is typically single-stranded and can fold into complex secondary
structures. Adenine is found in both DNA and RNA .
7. The nitrogenous base attaches to which carbon of the ribose or deoxyribose sugar?
A) The 1' carbon
B) The 2' carbon
C) The 3' carbon
D) The 5' carbon
Answer: A
Rationale: The nitrogenous base is attached to the 1' carbon of the sugar molecule. The 5'
carbon attaches to the phosphate group, and the 3' carbon has a hydroxyl group involved in
phosphodiester bond formation .
8. In a DNA molecule, the 5' end contains a free _________________ group.
A) Phosphate
B) Hydroxyl
C) Amino
D) Carboxyl
Answer: A
Rationale: In a DNA molecule, the 5' end contains a free phosphate group, while the 3' end
contains a free hydroxyl group .
9. Which enzyme untangles DNA during replication?
A) Polymerase
B) Helicase
C) Kinase
D) Phosphatase
Answer: B
Rationale: Helicase unwinds and untangles the DNA double helix for replication .
10. Which type of restriction enzyme is commonly used in the laboratory?
A) Type I
B) Type II
C) Type III
D) Type IV
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Answer: B
Rationale: Type II restriction enzymes are commonly used in the laboratory. They recognize 4-6
bp palindromic sequences and cut within the recognition sequence .
Chapter 4 — Collection, Isolation, and Quantification of Nucleic Acids
11. Which whole blood fraction is the most abundant source of genomic DNA?
A) Plasma
B) Serum
C) Buffy coat
D) Red blood cells
Answer: C
Rationale: The buffy coat, which contains white blood cells, is the most abundant source of
genomic DNA in whole blood .
12. Which specimen will yield the best DNA preparation?
A) Fresh blood
B) Frozen blood
C) Formalin-fixed tissue
D) Paraffin-embedded tissue
Answer: A
Rationale: Fresh blood yields the best DNA preparation. Formalin-fixed and paraffin-embedded
tissues can damage nucleic acids .
13. The concentration of agarose in a gel determines the size of spaces in the gel. 3% agarose
resolution is best for _______ bp of DNA.
A) 50-100 bp
B) 500-1,000 bp
C) 1,000-5,000 bp
D) 20,000-50,000 bp
Answer: A
Rationale: 3% agarose is best for resolving 50-100 bp DNA fragments. Lower concentrations
(0.6%) are best for 1,000-20,000 bp .
14. What is the advantage of SYBR green over ethidium bromide for gel electrophoresis
nucleic acid staining?
A) SYBR green is more sensitive
B) SYBR green is not a mutagen and is less toxic
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MOLECULAR DIAGNOSTICS (4TH EDITION) EXAM QUESTIONS AND
CORRECT ANSWERS LATEST EDITION 2026
Molecular Diagnostics (4th Edition) – Complete Test Bank & Exam Practice Questions
Chapter 1 — Fundamentals of Molecular Biology
1. A medical technologist is explaining the central dogma of molecular biology to a new
laboratory trainee. According to the textbook's foundational concepts, which of the following
best describes the flow of genetic information in a eukaryotic cell?
A) Protein → RNA → DNA
B) DNA → Protein → RNA
C) DNA → RNA → Protein
D) RNA → DNA → Protein
Answer: C
Rationale: The central dogma of molecular biology describes the flow of genetic information as
DNA being transcribed into RNA, which is then translated into protein. This process involves
transcription (DNA to mRNA) and translation (mRNA to protein). Retroviruses are an exception,
using reverse transcriptase to convert RNA to DNA .
2. A researcher is analyzing a DNA sequence and needs to identify the directionality of the
strand. The 5' carbon connects to which functional group on the adjacent nucleotide?
A) The 1' carbon
B) The 3' hydroxyl group
C) The 5' phosphate group
D) The nitrogenous base
Answer: B
Rationale: The 5' carbon of one nucleotide connects to the hydroxyl group on the 3' ribose
carbon of the previous nucleotide through a phosphodiester bond .
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3. A laboratory scientist is studying RNA function and notes that ribosomal RNA (rRNA)
comprises what percentage of cellular RNA?
A) 10-20%
B) 30-40%
C) 50-60%
D) 80-90%
Answer: D
Rationale: Ribosomal RNA (rRNA) makes up 80-90% of cellular RNA and serves as an important
structural and functional component of ribosomes, which synthesize proteins. In prokaryotes,
the small subunit contains 16S rRNA, while the large subunit contains 23S and 5S rRNA .
4. During mRNA processing, which of the following modifications occurs at the 5' end?
A) Polyadenylation
B) Addition of a modified guanine cap
C) Splicing of exons
D) Addition of a methyl group
Answer: B
Rationale: During mRNA processing, the 5' end of mRNA is capped with a modified guanine
nucleotide. This cap is unique in that it involves a 5'-5' bond, rather than the standard 5'-3' bond
typically found in polynucleotides. Other processing steps include 3' polyadenylation and
splicing .
5. Which RNA polymerase is responsible for synthesizing messenger RNA (mRNA)?
A) RNA polymerase I
B) RNA polymerase II
C) RNA polymerase III
D) RNA polymerase IV
Answer: B
Rationale: In eukaryotic cells, RNA polymerase II synthesizes mRNA, which serves as the genetic
messenger that can be translated into protein. RNA polymerase I synthesizes rRNA, and RNA
polymerase III synthesizes tRNA and other small RNAs .
6. Which of the following is a characteristic of RNA but not DNA?
A) Contains adenine
B) Contains a double helix structure
C) Contains uracil instead of thymine
D) Contains deoxyribose sugar
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Answer: C
Rationale: RNA contains uracil instead of thymine and has a ribose sugar rather than
deoxyribose. Unlike DNA, RNA is typically single-stranded and can fold into complex secondary
structures. Adenine is found in both DNA and RNA .
7. The nitrogenous base attaches to which carbon of the ribose or deoxyribose sugar?
A) The 1' carbon
B) The 2' carbon
C) The 3' carbon
D) The 5' carbon
Answer: A
Rationale: The nitrogenous base is attached to the 1' carbon of the sugar molecule. The 5'
carbon attaches to the phosphate group, and the 3' carbon has a hydroxyl group involved in
phosphodiester bond formation .
8. In a DNA molecule, the 5' end contains a free _________________ group.
A) Phosphate
B) Hydroxyl
C) Amino
D) Carboxyl
Answer: A
Rationale: In a DNA molecule, the 5' end contains a free phosphate group, while the 3' end
contains a free hydroxyl group .
9. Which enzyme untangles DNA during replication?
A) Polymerase
B) Helicase
C) Kinase
D) Phosphatase
Answer: B
Rationale: Helicase unwinds and untangles the DNA double helix for replication .
10. Which type of restriction enzyme is commonly used in the laboratory?
A) Type I
B) Type II
C) Type III
D) Type IV
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Answer: B
Rationale: Type II restriction enzymes are commonly used in the laboratory. They recognize 4-6
bp palindromic sequences and cut within the recognition sequence .
Chapter 4 — Collection, Isolation, and Quantification of Nucleic Acids
11. Which whole blood fraction is the most abundant source of genomic DNA?
A) Plasma
B) Serum
C) Buffy coat
D) Red blood cells
Answer: C
Rationale: The buffy coat, which contains white blood cells, is the most abundant source of
genomic DNA in whole blood .
12. Which specimen will yield the best DNA preparation?
A) Fresh blood
B) Frozen blood
C) Formalin-fixed tissue
D) Paraffin-embedded tissue
Answer: A
Rationale: Fresh blood yields the best DNA preparation. Formalin-fixed and paraffin-embedded
tissues can damage nucleic acids .
13. The concentration of agarose in a gel determines the size of spaces in the gel. 3% agarose
resolution is best for _______ bp of DNA.
A) 50-100 bp
B) 500-1,000 bp
C) 1,000-5,000 bp
D) 20,000-50,000 bp
Answer: A
Rationale: 3% agarose is best for resolving 50-100 bp DNA fragments. Lower concentrations
(0.6%) are best for 1,000-20,000 bp .
14. What is the advantage of SYBR green over ethidium bromide for gel electrophoresis
nucleic acid staining?
A) SYBR green is more sensitive
B) SYBR green is not a mutagen and is less toxic
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