CSMLS Molecular Diagnostics

Question 1

What is the primary purpose of the denaturation step in PCR?

Accepted Answer

To separate double-stranded DNA into single strands

Answer

To allow primers to bind to the template

Answer

To synthesize new DNA strands using polymerase

Answer

To remove RNA contamination from the sample

Question 2

Why is Taq polymerase used in PCR instead of a standard DNA polymerase?

Accepted Answer

It is thermostable and survives repeated heating to 94°C

Answer

It has higher fidelity and fewer errors

Answer

It can amplify RNA directly without reverse transcription

Answer

It requires no cofactors or dNTPs

Question 3

In quantitative real-time PCR (qPCR), what does the Ct (cycle threshold) value represent?

Accepted Answer

The cycle at which fluorescence crosses the detection threshold

Answer

The total number of PCR cycles programmed

Answer

The melting temperature of the amplified product

Answer

The concentration of primers in the reaction

Question 4

Which technique is used to detect RNA viruses such as HIV or Hepatitis C virus by molecular methods?

Accepted Answer

Reverse transcriptase PCR (RT-PCR)

Answer

Southern blotting

Answer

Pulsed-field gel electrophoresis

Answer

Loop-mediated isothermal amplification

Question 5

SYBR Green dye in qPCR generates signal by:

Accepted Answer

Intercalating into any double-stranded DNA formed during amplification

Answer

Binding specifically to the primer-template junction

Answer

Hybridizing to a specific probe sequence on the amplicon

Answer

Fluorescing when cleaved by the 5'-to-3' exonuclease activity of Taq

Question 6

Fluorescence in situ hybridization (FISH) is primarily used in molecular diagnostics to:

Accepted Answer

Detect specific DNA sequences or chromosomal rearrangements in intact cells

Answer

Amplify specific gene sequences for sequencing

Answer

Quantify mRNA expression levels in tissue samples

Answer

Determine antibiotic resistance profiles of bacteria

Question 7

Which electrophoresis technique is best suited for separating very large DNA fragments greater than 50 kilobases?

Accepted Answer

Pulsed-field gel electrophoresis (PFGE)

Answer

Agarose gel electrophoresis

Answer

Polyacrylamide gel electrophoresis

Answer

Capillary electrophoresis