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

When analyzing a clinical case, which staining technique helps determine the chromosomal origin of a small extra marker with satellites?

1. FISH

2. G-banding

3. NOR staining

4. RAPD

The correct answer is: NOR staining

The correct approach to determining the chromosomal origin of a small extra marker with satellite regions is through NOR staining. This technique specifically targets nucleolar organizer regions (NORs), which are associated with rRNA gene clusters that play a significant role in the formation of nucleoli within interphase cells. When you suspect that an extra marker could be derived from chromosomal regions associated with these rRNA genes, NOR staining can help visualize them effectively. By highlighting the regions of chromosomes that contain NORs, this technique can provide insight into whether the small extra marker has characteristics indicative of these specific chromosomal regions. The presence of satellites, often found on acrocentric chromosomes, further supports the utility of NOR staining as it allows the identification of additional structural elements and their relationship to nucleolar activity. Other techniques, while valuable for various aspects of cytogenetic analysis, have different specific applications. For instance, FISH is excellent for detecting specific DNA sequences but may not provide information about the chromosomal location of markers with satellites specifically. G-banding is useful for providing a general karyotype and identifying structural rearrangements, but it may not resolve the detailed information needed for identifying small markers. RAPD (Random Amplified Polymorphic DNA) is primarily a method