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

What banding technique should be performed first if sequential banding is necessary?

1. C-banding

2. G-banding

3. Q-banding

4. R-banding

The correct answer is: Q-banding

In sequential banding techniques, the order of performing different banding methods is crucial for proper interpretation and analysis of chromosomal abnormalities. Q-banding should be the first technique performed because it produces characteristic banding patterns that are highly useful for visualizing the distribution of DNA along the chromosomes. Q-banding primarily utilizes the fluorochrome quinacrine, which highlights specific regions of the chromosomes, allowing for the identification of crucial features such as centromeric and telomeric regions. As the first step, Q-banding provides an overview that can guide subsequent banding methods. Following Q-banding, additional techniques like G-banding or R-banding can be undertaken, which further enhance the chromosomal resolution and cytogenetic analysis. Each method provides different types of information, with G-banding being particularly productive for routine karyotyping and R-banding giving an alternative view of banding patterns. The sequential approach begins with Q-banding due to its ability to provide comprehensive and detailed information that is essential for any further analysis.