American Society for Clinical Pathology (ASCP) Technologist in Cytogenetics certification (ASCP CG) Practice Test

What methodology is used to confirm the deletion of the ARSA region in a patient?

1. Cytogenetic microdissection

2. Fluorescence in situ hybridization (FISH)

3. Polymerase chain reaction (PCR)

4. Chromosomal banding techniques

The correct answer is: Fluorescence in situ hybridization (FISH)

Fluorescence in situ hybridization (FISH) is a powerful technique used to confirm deletions at specific chromosomal regions, such as the ARSA region. FISH employs fluorescent probes that bind to particular regions of chromosomes, allowing for visualization of chromosomal abnormalities directly in interphase or metaphase cells. This method is particularly effective for demonstrating deletions, as it can show the presence or absence of signals from the fluorescent probes that correspond to the target area on the chromosome. When confirming a deletion, FISH can compare the intensity of signals in the patient’s cells with those in control cells. If the ARSA region is deleted in the patient's genome, a significant reduction or complete absence of the fluorescent signal for that specific probe will be observed, indicating that the region is missing. This capability makes FISH not only a confirmatory tool but also a routine methodology in clinical cytogenetics for evaluating genetic material. Other methodologies have different applications and limitations. Cytogenetic microdissection is primarily used to isolate and study specific chromosomal regions but is less effective for routine diagnosis and confirmation of deletions. Polymerase chain reaction (PCR), while sensitive for detecting genetic material, does not provide direct visualization of chromosomal structure and is better suited for