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

What could be a reason a metaphase cannot be located when switching from a 40x lens to a 100x oil lens?

1. The 100x objective is too focused

2. The 100x objective is slightly unscrewed

3. The sample slide is damaged

4. The 40x lens is misaligned

The correct answer is: The 100x objective is slightly unscrewed

The reason a metaphase might not be located when switching from a 40x lens to a 100x oil lens could indeed relate to the positioning of the 100x objective. If the 100x objective is slightly unscrewed, it may not be properly aligned or positioned within the optical path of the microscope. This misalignment could prevent the user from achieving a clear focus on the metaphase stage, which is critical for observing chromosomal details. In microscopy, particularly with high magnification objectives like the 100x oil lens, precise alignment is essential for proper focusing. When the lens is not fully secured, slight movements can lead to an inability to locate specific structures, such as the metaphase chromosomes, which require meticulous focusing and alignment to be visible. While other options may influence the visibility of the metaphase, such as sample slide damage which could obscure the view, or misalignment of the 40x lens possibly impacting the transitioning of focus, the most direct and immediate issue affecting the ability to locate metaphase cells when switching objectives is tied to the mounting of the 100x lens itself. When lenses are correctly aligned and secured, the transition from a lower to a higher magnification should allow for a clear view of the sample