Medical Laboratory TechnicianĀ Exam Molecular Diagnostics 1 ā Questions and Answers
Question 1: Which technique is used to amplify specific DNA sequences in molecular diagnostics?
- Southern blot
- Polymerase chain reaction (PCR) (Correct answer)
- Western blot
- ELISA
Correct answer: Polymerase chain reaction (PCR)
PCR (polymerase chain reaction) uses thermal cycling with DNA polymerase to exponentially amplify specific DNA sequences.
Question 2: What is the purpose of the denaturation step in PCR?
- To anneal primers to template DNA
- To extend new DNA strands
- To separate double-stranded DNA into single strands (Correct answer)
- To remove RNA from the sample
Correct answer: To separate double-stranded DNA into single strands
Denaturation (typically at 94-98Ā°C) breaks the hydrogen bonds between complementary base pairs, separating double-stranded DNA into single strands so primers can bind.
Question 3: Which enzyme is essential for the PCR amplification process?
- RNA polymerase
- Ligase
- Taq polymerase (Correct answer)
- Restriction endonuclease
Correct answer: Taq polymerase
Taq polymerase, derived from Thermus aquaticus, is a heat-stable DNA polymerase that can withstand the high temperatures used in PCR cycling.
Question 4: In real-time PCR (qPCR), fluorescence is measured to:
- Determine the size of the amplified product
- Quantify the amount of target DNA during amplification (Correct answer)
- Identify the sequence of the amplicon
- Detect chromosomal abnormalities
Correct answer: Quantify the amount of target DNA during amplification
In real-time PCR, fluorescent dyes or probes generate a signal proportional to the amount of amplified DNA, allowing quantification during each cycle.
Question 5: Which molecular technique is used to detect RNA viruses such as HIV or SARS-CoV-2?
- Standard PCR
- Reverse transcriptase PCR (RT-PCR) (Correct answer)
- Southern blot
- Pulsed-field gel electrophoresis
Correct answer: Reverse transcriptase PCR (RT-PCR)
RT-PCR first converts RNA into complementary DNA (cDNA) using reverse transcriptase before PCR amplification, making it suitable for RNA virus detection.
Question 6: What does a Southern blot technique detect?
- Specific RNA sequences
- Specific DNA sequences (Correct answer)
- Specific proteins
- Specific antibodies
Correct answer: Specific DNA sequences
Southern blotting transfers denatured DNA from a gel to a membrane, where it is hybridized with a labeled probe to detect specific DNA sequences.
Question 7: Which specimen collection tube is most appropriate for molecular testing of whole blood?
- Red top (no additive)
- Yellow top (SPS)
- Lavender top (EDTA) (Correct answer)
- Light blue top (sodium citrate)
Correct answer: Lavender top (EDTA)
EDTA (lavender top) tubes are preferred for molecular testing of whole blood because EDTA chelates calcium, preventing DNA degradation and inhibiting nuclease activity.
Medical Laboratory TechnicianĀ Exam Molecular Diagnostics 1
Which technique is used to amplify specific DNA sequences in molecular diagnostics?