MLPAO Laboratory Techniques and Procedures Questions and Answers 2

Question 1

What technique is used to separate DNA fragments by size during gel electrophoresis?

Accepted Answer

Migration through an agarose gel matrix under an electrical current

Answer

DNA fragments migrate through an agarose gel under electrical current — smaller fragments move faster through the gel matrix than larger fragments, separating them by size.

Question 2

What is the principle of the polymerase chain reaction (PCR) in molecular diagnostics?

Accepted Answer

Amplification of specific DNA sequences through repeated cycles of denaturation, annealing, and extension

Answer

PCR amplifies specific DNA sequences exponentially through repeated thermal cycles: denaturation (94-98°C) separates strands, annealing (50-65°C) allows primers to bind, and extension (72°C) allows Taq polymerase to copy the target.

Question 3

In clinical microbiology, what is the purpose of inoculating a blood agar plate and a chocolate agar plate simultaneously when processing a respiratory specimen?

Accepted Answer

Blood agar detects beta-hemolytic organisms; chocolate agar supports fastidious organisms like Haemophilus and Neisseria that require growth factors released by heated RBCs

Answer

Blood agar supports most bacteria and shows hemolysis patterns; chocolate agar (heated blood agar) releases NAD and hemin from lysed RBCs, supporting fastidious organisms such as Haemophilus influenzae and Neisseria species.

Question 4

Which laboratory method is used as the reference (gold standard) for diagnosing malaria?

Accepted Answer

Microscopic examination of Giemsa-stained thick and thin blood films

Answer

Microscopic examination of Giemsa-stained thick and thin blood films is the reference standard for malaria diagnosis, allowing species identification and parasitemia quantification.

Question 5

What type of pipette is most appropriate for delivering a precise volume of 100 μL for an ELISA assay?

Accepted Answer

Calibrated micropipette (100 μL fixed or adjustable)

Answer

A calibrated micropipette set to 100 μL delivers precise, accurate volumes for immunoassays like ELISA. Accuracy is critical because volume errors directly affect the antigen-antibody ratio and results.

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO Laboratory Techniques and Procedures Questions and Answers 2