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

What is the purpose of NOR banding in cytogenetics?

1. To identify centromeres

2. To confirm the presence of satellites

3. To analyze chromosomal structure

4. To differentiate between heterochromatin and euchromatin

The correct answer is: To confirm the presence of satellites

NOR banding, or nucleolar organizer region banding, is primarily used to identify the presence of nucleolar organizer regions (NORs) on chromosomes. These NORs correspond to the regions of chromosomes that are associated with the formation of the nucleolus and are typically found on the short arms of acrocentric chromosomes. When NOR banding is performed, it highlights these regions, allowing cytogeneticists to confirm their presence through the visualization of specific banding patterns. This technique is particularly useful in the identification of chromosomes that contain NORs during chromosome analysis, making it a vital tool for understanding chromosomal architecture and function related to ribosomal RNA synthesis. Different types of banding techniques yield insights into chromosomal characteristics, but NOR banding is distinctively focused on delineating the nucleolar organizer regions. The other answers do not align as closely with the primary aim of NOR banding. Identifying centromeres is usually carried out using different banding techniques that highlight centromeric regions specifically. Analyzing chromosomal structure can encompass a variety of methods that do not focus exclusively on NORs. Differentiating between heterochromatin and euchromatin is typically achieved through other banding techniques such as G-banding or C-b