ASCP BOC Scientist in Cytogenetics (CG) Examination Practice Test
Cytogenetics examines chromosome number and structure to identify changes relevant to constitutional and acquired disorders. This practice page’s questions sample chromosome preparation and banding, resolution, fluorescence in situ hybridization (FISH), and the capabilities and limits of chromosome-based methods such as chromosomal microarray analysis.
Exam overview
About the ASCP BOC Scientist in Cytogenetics (CG) Examination Exam
Cytogenetic laboratory work requires connecting specimen quality and preparation with interpretable results. Chromosome analysis involves assessing metaphase quality, recognizing banding patterns, and describing numerical or structural changes, including distinctions among rearrangements. FISH questions address probe design, signal patterns, hybridization controls, and technical factors that can weaken signals across cells. Method selection also matters: chromosome banding, targeted FISH, and microarray analysis detect different types of changes, so their findings and limitations must be interpreted in context. Practice with these concepts can help build familiarity with how laboratory observations support accurate characterization and reporting of chromosome abnormalities.
Sample Practice Questions
Review a selection from this exam's published US Practice Tests practice bank.
A chromosome preparation has banding that is too dark and indistinct for reliable identification. Which change to the banding treatment would generally be appropriate to improve resolution?
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Correct answer: BExcessive protease digestion can make chromosome bands overly dark or indistinct and damage chromosome morphology. Shortening digestion is a common adjustment, followed by evaluation of the resulting banding. The optimal treatment depends on the preparation and laboratory protocol.
Which statement best describes the limitation of chromosomal microarray analysis compared with a balanced-rearrangement assay?
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Correct answer: AChromosomal microarray measures relative DNA dosage and can detect many copy-number changes, but a balanced rearrangement with no net gain or loss may not produce a dosage signal. Other methods, such as chromosome analysis or targeted assays, may be needed to assess such rearrangements.
For a constitutional chromosome study, a laboratory reports that analysis was performed at approximately 550-band resolution. What does this value primarily describe?
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Correct answer: ABand-level resolution estimates the degree of chromosome detail visible in the karyotype, conventionally described by the approximate number of bands per haploid set. It is distinct from the number of cells analyzed or the percentage of abnormal cells.
What is the main purpose of adding colcemid or a similar spindle inhibitor during chromosome culture?
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Correct answer: ASpindle inhibitors interfere with microtubule function and prevent normal metaphase progression, enriching the culture for metaphase cells suitable for chromosome analysis.
Which feature most directly distinguishes a reciprocal translocation from an insertional rearrangement in chromosome analysis?
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Correct answer: AA reciprocal translocation is generally described as an exchange of segments between chromosomes. An insertion involves a segment inserted into another location and does not inherently require a reciprocal exchange. Whether either rearrangement is detected depends on its size, structure, and the method used.
In a FISH assay, fluorescent signals are weak across nearly all nuclei, including those expected to show the target sequence. Which general technical concern should be considered first?
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Correct answer: BWeak or absent signals across expected positive nuclei can indicate a technical problem, such as inadequate hybridization, probe quality, or detection conditions. Results should be assessed against assay controls and acceptance criteria before biological conclusions are made.
A laboratory receives a peripheral blood specimen for constitutional chromosome analysis. Which factor is most important when deciding whether the specimen remains suitable for culture?
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Correct answer: ACell viability is important for successful culture, so specimen integrity, transport temperature, and time before processing should be considered according to laboratory requirements. Repeated freezing and thawing can compromise viable cells; tube-cap color alone does not establish suitability.
How to use this practice test
The free practice bank contains 50 published questions. Each session presents up to 20 questions selected at random, with results shown after the session. Use the results to identify concepts to revisit, such as banding resolution, rearrangement patterns, specimen suitability, or FISH signal interpretation.
Preparation tips
- Compare reciprocal translocations and insertional rearrangements by tracing which chromosome segments move and where they are inserted.
- Review how metaphase arrest, chromosome banding treatment, and band-level resolution affect the quality and interpretability of a karyotype.
- Practice interpreting break-apart FISH patterns and distinguish a target-specific result from weak signals across nearly all nuclei.
- Contrast chromosomal microarray with chromosome analysis and FISH, especially for balanced rearrangements and changes each method may not detect.
- For specimen scenarios, consider collection and transport conditions that can affect cell viability and successful culture.