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

After staining, if chromosomes appear muddy and dark, what should be done to correct the problem?

1. Decrease trypsin exposure

2. Increase trypsin exposure

3. Add more stain

4. Change the temperature

The correct answer is: Increase trypsin exposure

When chromosomes appear muddy and dark after staining, it is often indicative of insufficient chromosome spreading or poor-quality slides. Increasing trypsin exposure can help to enhance the clarity of the chromosomes by ensuring more effective and uniform pretreatment. Trypsin plays a vital role in the process of preparing chromosomes for staining by digesting proteins that can interfere with clear staining patterns. A longer exposure to trypsin allows for better chromosome morphology to emerge, leading to improved visibility. This adjustment can help differentiate the various structures within the chromosomes, allowing for a clearer analysis and interpretation during cytogenetic examination. In contrast, decreasing trypsin exposure would likely exacerbate the problem by preventing adequate digestion of proteins, leading to even muddier appearances. Adding more stain may not solve the underlying issue of poor chromosome preparation; it could lead to over-staining, which would worsen the visibility by creating additional background noise. Changing the temperature could affect the enzymatic activity but is not a direct solution to correcting the muddy appearance of chromosomes. Thus, increasing trypsin exposure is the appropriate action to enhance the quality of the chromosome preparation.