Answer:
The correct answer is:
B) When the PCR reaction contains contaminants
Explanation:
In molecular biology, particularly in techniques like polymerase chain reaction (PCR), a negative control is included to ensure that any signal observed is due to the target of interest and not due to contamination or other non-specific factors.
The negative control typically consists of the same reaction components as the experimental samples but lacks the template DNA or RNA. In qPCR (quantitative PCR), the negative control often includes water and the qPCR mix.
If a signal is observed in the negative control containing water and qPCR mix, it suggests the presence of contaminants in the reaction mixture. These contaminants could potentially interfere with the amplification process, leading to false-positive results.
Therefore, seeing a signal in the negative control indicates that the PCR reaction may contain contaminants, which could affect the accuracy and reliability of the experimental results.
