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

What temperature is recommended for FITC-avidin storage in FISH procedures?

1. -20°C

2. 25°C

3. 4°C

4. 32°C

The correct answer is: 4°C

The recommended storage temperature for FITC-avidin in Fluorescence In Situ Hybridization (FISH) procedures is 4°C. Storing FITC-avidin at this temperature helps maintain the stability and integrity of the reagent, ensuring its effectiveness during hybridization and fluorescent labeling processes. At 4°C, the protein is kept cool enough to slow down potential degradation or loss of functionality, which is critical for achieving reliable and high-quality results in cytogenetic analysis. Storing FITC-avidin at higher temperatures, such as room temperature (25°C) or elevated temperatures (32°C), could lead to degradation or reduced activity of the avidin due to the increased kinetic energy, impacting the binding capabilities essential for accurate FISH results. Similarly, while freezing at -20°C might seem like a good preservation strategy, it could also precipitate or denature proteins, leading to unpredictable outcomes in the assay. Therefore, the 4°C storage recommendation strikes an optimal balance for preserving the reagent's stability and performance in FISH applications.