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

What type of light source can cause fluorescence in cytogenetic techniques?

1. Halogen lamps

2. Mercury vapor lamps

3. Xenon lamps

4. LED lights

The correct answer is: Mercury vapor lamps

In cytogenetic techniques, fluorescence is a critical component used to visualize and analyze chromosomes. Mercury vapor lamps are particularly effective as light sources for fluorescence because they emit a strong ultraviolet (UV) light. This UV light excites the fluorescent dyes that are often used to stain chromosomes or other cellular components, causing them to emit light at a longer wavelength. This principle is key in techniques such as fluorescence in situ hybridization (FISH), where specific DNA sequences are targeted by fluorescent probes, enabling researchers to detect and visualize genetic abnormalities or chromosomal structures. While other light sources like halogen lamps, xenon lamps, and LED lights can provide illumination for imaging, they do not have the necessary properties to generate fluorescence effectively in the same way as mercury vapor lamps. In particular, halogen lamps emit visible light and do not produce the UV wavelengths required to excite fluorescent dyes, while xenon lamps, although they can emit some UV light, generally lack the intensity needed for optimal fluorescence in cytogenetic applications. LEDs, while versatile, have traditionally been used in less demanding fluorescence applications and may not provide the specific wavelength and intensity profiles that are needed for effective fluorescence in cytogenetics.