Free ASCP BOC Scientist in Cytogenetics (CG) Examination Practice Questions

Sample Practice Questions

Try these 10 sample questions from the ASCP BOC Scientist in Cytogenetics (CG) Examination practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1A chorionic villus specimen is being prepared for fetal chromosome analysis. Which preparation most directly reduces maternal cell contamination?

   1. A. Retain maternal decidua to increase the amount of tissue cultured.
   2. B. Dissect fetal villi away from maternal decidua before initiating cultures.
   3. C. Combine the villi and maternal blood before dividing the cultures.
   4. D. Select only the largest tissue fragments without microscopic inspection.

   Answer: B

   Explanation: ACMG recommends using sterile instruments "to isolate the fetal chorionic villi from maternal decidua." Dissection under a dissecting microscope removes maternal tissue that could otherwise grow and confound the fetal result.

   Reference: ACMG Technical Standards for Clinical Genetics Laboratories: Clinical Cytogenetics — E3.3.1.2, Chorionic Villi Sampling

2. 2A laboratory wants to detect whether a gene is rearranged when several different translocation partners are possible and no single partner is suspected. Which FISH strategy is designed for that goal?

   1. A. A dual-fusion probe set for one specified partner pair.
   2. B. A centromere enumeration probe for the gene's chromosome.
   3. C. A break-apart probe set flanking the gene region.
   4. D. A single locus probe used only to count intact gene copies.

   Answer: C

   Explanation: The Wisconsin laboratory explains that "a break apart probe is used to test whether the gene of interest is involved in a rearrangement." This strategy detects separation of flanking regions without needing a specified fusion partner; the other strategies test a particular fusion or copy number.

   Reference: Fluorescent In Situ Hybridization (FISH) — Wisconsin State Laboratory of Hygiene — Different types of probes: Break Apart

3. 3In an epifluorescence microscope, which component selects the portion of the light source spectrum used to illuminate a fluorophore?

   1. A. Emission filter
   2. B. Excitation filter
   3. C. Field diaphragm
   4. D. Condenser phase annulus

   Answer: B

   Explanation: The handbook states, "The excitation filter selectively transmits a portion of the spectral output from the light source". The emission filter acts on the detection path; the diaphragms and phase annulus control other aspects of illumination.

   Reference: Selecting Optical Filters for Fluorescence Microscopy — Molecular Probes Handbook, Note 23.2 — The Optical Filter Set

4. 4Under ACMG general specimen-labeling guidance, which primary-container label provides the required two patient identifiers?

   1. A. Patient name and the laboratory room number.
   2. B. Patient name and the specimen collection date alone.
   3. C. Hospital name and the type of test requested.
   4. D. Patient name and a unique hospital identification number.

   Answer: D

   Explanation: ACMG says primary containers "must include two identifiers" and lists patient name and hospital number as examples. Collection date is separately requested information; room, institution, and test names do not uniquely identify the patient.

   Reference: ACMG Technical Standards for Clinical Genetics Laboratories: General Policies — C2.1, Specimens and Intake Information

5. 5Which statement explains the recommended separate handling of the first few milliliters collected during amniocentesis?

   1. A. The first aliquot is preferred because it is less likely to contain maternal cells.
   2. B. The first aliquot provides an uncontaminated control for the later fluid.
   3. C. The first aliquot has a higher risk of maternal cells confounding fetal analysis.
   4. D. The first aliquot should replace later fluid whenever fetal culture is needed.

   Answer: C

   Explanation: ACMG states that cultures from the first 1–2 mL "are at an increased risk for maternal cell contamination". Keeping that aliquot separate minimizes maternal-cell inclusion; it is not an uncontaminated control or the preferred routine culture aliquot.

   Reference: ACMG Technical Standards for Clinical Genetics Laboratories: Clinical Cytogenetics — E3.3.1.1, Amniotic Fluid

6. 6During FISH processing, what is the principal purpose of the controlled-temperature hybridization incubation after DNA denaturation?

   1. A. To allow complementary probes to bind the target DNA.
   2. B. To remove excess probe by high-stringency washing.
   3. C. To counterstain the nuclei for evaluation of cell boundaries.
   4. D. To digest proteins so the probes can penetrate the specimen.

   Answer: A

   Explanation: The training resource states that incubation at a set temperature "allows the probes to bind to the target DNA." Washing, counterstaining, and pretreatment serve different stages of FISH processing.

   Reference: Preparation of Samples for Cytogenetic Analysis: Model Answers — Pages 7–8, Bookmark 4, item 30

7. 7Which fluorescence microscope component blocks residual excitation light and unwanted emitted wavelengths before they reach the detector?

   1. A. Excitation filter
   2. B. Condenser aperture diaphragm
   3. C. Phase plate
   4. D. Emission filter

   Answer: D

   Explanation: The handbook explains, "The emission filter blocks unwanted spectral components of the emitted fluorescence" and residual excitation light. It isolates the detection band rather than selecting the illumination band.

   Reference: Selecting Optical Filters for Fluorescence Microscopy — Molecular Probes Handbook, Note 23.2 — The Optical Filter Set

8. 8Which reagent label is consistent with ACMG C6.5 for a laboratory-prepared solution?

   1. A. Contents, concentration, preparation date, storage shelf location, and expiration date.
   2. B. Contents, concentration, receipt date, storage conditions, and expiration date.
   3. C. Contents, concentration, preparation date, storage conditions, and expiration date.
   4. D. Contents, concentration, preparation date, storage conditions, and purchase date.

   Answer: C

   Explanation: ACMG specifies "content and concentration information, preparation date, storage conditions, and the expiration date." Receipt does not replace preparation date, shelf location does not describe required storage conditions, and purchase date does not replace expiration.

   Reference: ACMG Technical Standards for Clinical Genetics Laboratories: General Policies — C6.5, Reagent identification

9. 9For chromosome analysis of products of conception, which tissue-selection approach best addresses the risk that a culture could represent the mother rather than the conceptus?

   1. A. Identify and dissect fetal tissue before establishing the culture.
   2. B. Prefer maternal decidua because it often grows more readily.
   3. C. Pool all placental and maternal fragments to maximize cell yield.
   4. D. Choose the tissue solely by its ability to attach to the flask.

   Answer: A

   Explanation: For products of conception, ACMG recommends measures "to specifically identify fetal tissues and to dissect and culture only these tissues". Growth or attachment alone does not establish fetal origin.

   Reference: ACMG Technical Standards for Clinical Genetics Laboratories: Clinical Cytogenetics — E3.3.1.3, Products of Conception

10. 10What is the purpose of the DAPI counterstain in a FISH preparation?

    1. A. To amplify the fluorescent signal from the target-specific probe.
    2. B. To denature the target DNA before probe hybridization.
    3. C. To remove weakly bound probes during stringent washing.
    4. D. To visualize cells and chromosomes alongside the probe signals.

    Answer: D

    Explanation: The document describes DAPI as the stain "which visualises the cells and chromosomes whilst not masking the fluorescent FISH probes." It provides nuclear and chromosomal context rather than probe amplification, denaturation, or washing.

    Reference: Preparation of Samples for Cytogenetic Analysis: Model Answers — Page 8, Bookmark 4, item 33