ASCP Molecular Diagnostics 2

Question 1

In PCR, what is the role of the thermostable DNA polymerase (Taq polymerase)?

Accepted Answer

To synthesize new DNA strands using primers as starting points

Answer

Taq polymerase (from Thermus aquaticus) is a thermostable DNA polymerase that synthesizes new DNA strands by extending from the 3' end of primers using the template strand. Its heat stability allows repeated thermocycling.

Question 2

Southern blotting detects:

Accepted Answer

DNA sequences

Answer

Southern blotting (developed by Edwin Southern) detects specific DNA sequences. DNA is digested with restriction enzymes, separated by gel electrophoresis, transferred to a membrane, and hybridized with a labeled probe.

Question 3

A FISH break-apart probe is designed to:

Accepted Answer

Detect gene rearrangements by showing split signals when a gene is disrupted

Answer

Break-apart FISH probes flank a gene of interest with differently colored labels. In the normal state, signals are adjacent or fused. A chromosomal rearrangement splits the signals apart, indicating rearrangement regardless of the partner gene.

Question 4

Pharmacogenomic testing for CYP2D6 variants is clinically important because CYP2D6 metabolizes:

Accepted Answer

A large number of drugs including codeine, tamoxifen, and many antidepressants

Answer

CYP2D6 metabolizes approximately 25% of clinically used drugs, including codeine (to morphine), tamoxifen (to endoxifen), tricyclic antidepressants, SSRIs, and antipsychotics. Genetic variants create poor, intermediate, normal, rapid, and ultrarapid metabolizer phenotypes.

Question 5

Microsatellite instability (MSI) testing is most relevant for which condition?

Accepted Answer

Lynch syndrome (hereditary nonpolyposis colorectal cancer)

Answer

Lynch syndrome is caused by germline mutations in mismatch repair (MMR) genes (MLH1, MSH2, MSH6, PMS2). Deficient MMR causes MSI — length changes in repetitive DNA sequences. MSI-H tumors in young patients prompt Lynch syndrome evaluation.

ASCP Practice Test

ASCP Practice Test

ASCP Molecular Diagnostics 2