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

If GTG banded chromosomes appear ghost-like with little visible banding, what should be altered during the preparation?

1. Increase trypsin time

2. Decrease trypsin time

3. Increase staining time

4. Decrease staining temperature

The correct answer is: Decrease trypsin time

When GTG banding results in chromosomes that appear ghost-like with minimal visible banding, it indicates that there may have been excessive digestion of the chromosome spreads, leading to the loss of banding pattern detail. Since trypsin is the enzyme used during the GTG banding process, decreasing the trypsin time is a key adjustment to improve the visibility of chromosome bands. Reducing the time the chromosomes are exposed to trypsin ensures that the enzyme does not digest the chromatin too thoroughly, allowing for the preservation of the banding patterns that are critical for analysis. Adequate banding is essential for identifying chromosomal abnormalities, and a balance must be achieved in enzyme exposure time to prevent excessive digestion. Changes to staining time or temperature may alter the coloration or contrast of the bands but would not directly address the loss of structure that characterizes the ghost-like appearance. Therefore, decreasing trypsin time is the most effective approach to restoring the visibility of the chromosomal bands during preparation.