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

What do you add in order to detect sister chromatid exchange (SCE)?

1. Halothane

2. BrdU

3. 5-Bromo-2'-deoxyuridine

4. Adenosine triphosphate

The correct answer is: BrdU

To detect sister chromatid exchange (SCE), BrdU (5-Bromo-2'-deoxyuridine) is used because it is a thymidine analog that incorporates itself into replicating DNA during the S phase of the cell cycle. When cells are treated with BrdU, it replaces thymidine in the DNA strands. This incorporation allows researchers to use techniques such as fluorescence microscopy or cytogenetic staining to visualize chromatid structure during metaphase. During SCE detection, BrdU is essential as it marks the newly synthesized DNA strands with a specific chemical label. After the proper treatment and subsequent replication, SCE can be observed as the exchange of chromatid segments between the sister chromatids, which is distinguishable under appropriate staining techniques. This process is crucial for assessing genetic stability and is often used in cytogenetic studies to identify the effect of various agents on cell systems. The other options do not specifically contribute to the effective visualization and detection of SCE in this context. For instance, halothane is an anesthetic and does not have a role in DNA labeling or detection of chromatid exchange. Adenosine triphosphate (ATP) serves primarily as an energy currency in cells and does not play a direct