Molecular Diagnostics Flashcards
6 cards from real ASCP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Molecular Diagnostics flashcards as text
Reverse transcriptase PCR (RT-PCR) begins with which enzymatic step?
Answer: Conversion of mRNA to complementary DNA (cDNA) by reverse transcriptase
RT-PCR first uses reverse transcriptase (RNA-dependent DNA polymerase) to synthesize cDNA from an mRNA template. The resulting cDNA then serves as the template for standard PCR amplification.
Loss of heterozygosity (LOH) at a tumor suppressor gene locus typically indicates:
Answer: Deletion or mitotic recombination eliminating the wild-type allele
LOH occurs when the remaining wild-type allele of a tumor suppressor gene is lost through deletion, uniparental disomy, or mitotic recombination, leaving only the mutant allele — fulfilling Knudson's two-hit hypothesis for cancer development.
Which oncogene mutation is found in more than 90% of pancreatic adenocarcinomas?
Answer: KRAS (most commonly G12D)
KRAS mutations (predominantly G12D, G12V, and G12R) are found in more than 90% of pancreatic ductal adenocarcinomas (PDAC). KRAS encodes a GTPase; mutations lock it in the GTP-bound active form, driving continuous proliferative signaling.
The International Sensitivity Index (ISI) is used to calculate the INR. What is its purpose?
Answer: To standardize PT results across different laboratories using different thromboplastin reagents
Different thromboplastin reagents vary in sensitivity to reductions in vitamin K-dependent factors. The ISI calibrates each reagent against an international reference; the INR formula [INR = (PT patient/PT normal) to the power of ISI] normalizes results so warfarin monitoring is comparable across labs.
Which molecular technique provides the highest resolution for HLA allele-level typing?
Answer: Next-generation sequencing (NGS)
NGS provides the highest resolution allele-level HLA typing by generating phased sequence data, resolving ambiguities that arise with SSO, SSP, or Sanger sequencing. It is becoming the standard for unrelated donor searches in hematopoietic stem cell transplantation.
Digital PCR (dPCR) differs from real-time qPCR primarily in that dPCR:
Answer: Partitions samples into thousands of individual reactions to provide absolute copy number without a standard curve
Digital PCR partitions the sample into thousands of individual droplets or wells, each containing zero or one target molecule. After PCR amplification, counting positive versus negative partitions via Poisson statistics provides absolute copy number without a standard curve.