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

In cell culture, what does a peak in DNA synthesis indicate regarding cell division?

1. Cells are in the lag phase

2. Cells are undergoing rapid replication

3. Cells are in a stable phase

4. Cells are dying off

The correct answer is: Cells are undergoing rapid replication

A peak in DNA synthesis during cell culture is indicative of rapid cell replication. This point in the cell cycle is typically associated with the S phase, where DNA is actively being replicated in preparation for cell division. During this phase, the cells are engaged in synthesizing new DNA strands to ensure that when cell division occurs, each daughter cell receives an identical set of genetic material. When DNA synthesis is at its peak, it suggests that the cells are preparing to divide, which is crucial for cellular proliferation and growth. This behavior is characteristic of cells that are actively engaged in the cell cycle rather than in earlier phases, such as the lag phase, where cells are adapting to their environment and not yet replicating DNA. Similarly, cells in a stable phase, such as the G0 phase, are typically quiescent and not actively replicating DNA, while cell death does not correlate with peaks in DNA synthesis but rather suggests a decline in metabolic activity and cellular function.