ASCP Molecular Diagnostics

Question 1

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

Accepted Answer

The cycle at which fluorescence crosses a threshold above background

Answer

The Ct value is the PCR cycle number at which the fluorescence signal from a sample crosses a predefined threshold above background noise. Lower Ct values indicate more target DNA present. Higher Ct values indicate less target DNA.

Question 2

Which molecular technique is used to detect chromosomal translocations such as t(9;22) (BCR-ABL) in CML?

Accepted Answer

FISH and RT-PCR

Answer

Both FISH (fluorescence in situ hybridization) and RT-PCR (reverse transcription PCR) are used to detect t(9;22). FISH detects the chromosomal rearrangement; RT-PCR detects the BCR-ABL1 fusion mRNA and is used for quantitative minimal residual disease monitoring.

Question 3

BRCA1 and BRCA2 are tumor suppressor genes involved in DNA repair. Mutations in these genes primarily increase the risk of:

Accepted Answer

Breast and ovarian cancer

Answer

Pathogenic variants in BRCA1 and BRCA2 confer significantly elevated lifetime risk of breast cancer (approximately 70%) and ovarian cancer (approximately 44% for BRCA1, approximately 17% for BRCA2). BRCA2 also elevates pancreatic and male breast cancer risk.

Question 4

Which of the following best describes next-generation sequencing (NGS)?

Accepted Answer

Massively parallel sequencing of millions of DNA fragments simultaneously

Answer

NGS (also called massively parallel sequencing) sequences millions of short DNA fragments simultaneously, providing high throughput and depth of coverage unavailable with Sanger (first-generation) sequencing.

Question 5

Methylation-specific PCR (MSP) is used to detect which epigenetic modification?

Accepted Answer

DNA cytosine methylation at CpG sites

Answer

MSP detects DNA methylation at CpG dinucleotides. Bisulfite treatment converts unmethylated cytosines to uracil (read as thymine after PCR), while methylated cytosines are protected. MSP primers distinguish methylated from unmethylated alleles.

ASCP Practice Test

ASCP Practice Test

ASCP Molecular Diagnostics