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

What role does BrdU play in cytogenetic studies?

1. It acts as a fluorescent dye

2. It helps to stabilize RNA

3. It is used to detect sister chromatid exchanges

4. It serves as a growth factor

The correct answer is: It is used to detect sister chromatid exchanges

BrdU, or bromodeoxyuridine, is a synthetic nucleoside that is an analog of thymidine. In cytogenetic studies, BrdU is commonly used to label DNA during the S-phase of the cell cycle, where DNA synthesis occurs. By incorporating BrdU into newly synthesized DNA, researchers can later detect and visualize its presence using specific antibodies that bind to BrdU. This property is particularly valuable for studying sister chromatid exchanges, which are genetic events where segments of DNA are swapped between sister chromatids. By using BrdU in experiments, one can identify and quantify these exchanges, thereby providing insights into genomic stability and cellular processes like DNA repair and recombination. In the context of the other options, fluorescent dyes are used to stain cells for various types of imaging but do not specifically relate to the functions of BrdU regarding DNA synthesis. Stabilizing RNA does not pertain to BrdU's primary role in DNA labeling, and BrdU does not function as a growth factor, which is a substance that promotes cell proliferation. Thus, the primary relevance of BrdU in cytogenetics directly relates to its ability to detect and analyze sister chromatid exchanges.