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

Which of the following is NOT an effect of fixation?

1. A short exposure to Colcemid

2. Chromosome condensation

3. Prevention of enzymatic activity

4. Permanent preservation of tissue

The correct answer is: A short exposure to Colcemid

Colcemid is a drug that is commonly used in cytogenetics to disrupt the mitotic spindle, which leads to the accumulation of cells in metaphase and ultimately facilitates the examination of chromosomes during karyotyping. A short exposure to Colcemid is not an effect of fixation; rather, it is a technique used to manipulate cell cycles. Fixation, on the other hand, is a process that preserves the structure and morphology of cells and tissues by stabilizing proteins and nucleic acids, typically involving cross-linking agents like formaldehyde or ethanol. The other options relate to the effects of fixation: - Chromosome condensation occurs during cell division and is particularly relevant when preparing samples for karyotyping; fixation helps to preserve this state for observation. - Prevention of enzymatic activity is achieved through fixation, which denatures enzymes and halts any ongoing biological processes that could alter the sample. - Permanent preservation of tissue refers to fixation's role in stabilizing the cellular structure for long-term storage and analysis, ensuring the sample remains intact for future study. Thus, the short exposure to Colcemid is a procedural step rather than a consequence of fixation, supporting the conclusion that it does not represent an effect of fixation.