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

If media in the incubator has turned magenta and cell death has occurred, what is the most likely cause?

1. CO2 was too low

2. Oxygen levels were too high

3. The temperature was too high

4. The medium was contaminated

The correct answer is: CO2 was too low

The observation of magenta media in conjunction with cell death suggests that the pH of the culture medium has increased, leading to a color change due to the properties of the phenol red indicator commonly used in tissue culture media. This change can be indicative of a metabolic shift in the cells, which can occur in certain conditions. If carbon dioxide (CO2) levels in the incubator are too low, there will be insufficient CO2 to maintain an optimal pH through the carbonate-bicarbonate buffering system present in the medium. The lack of CO2 could lead to an alkaline shift in the medium due to decreased acid production from the cells. Consequently, this pH increase would result in the medium turning magenta, while elevated pH conditions can also contribute to cell stress or death. Therefore, low CO2 levels directly correlate with both the media color change and the cell death observed. In summary, the most likely cause of the magenta media coupled with cell death is an insufficient CO2 concentration, which disrupts the pH balance essential for maintaining cell viability in the culture.