Final Answer:
Quantitative Polymerase Chain Reaction (qPCR) detects gene expression by measuring the accumulation of amplified DNA during each cycle of the reaction. It utilizes fluorescent dyes or probes to monitor the progress of DNA amplification in real-time. The increase in fluorescence corresponds to the amount of target DNA, allowing for the quantification of gene expression levels.
Step-by-step explanation:
Quantitative Polymerase Chain Reaction (qPCR) is a powerful molecular biology technique used to quantify the amount of a specific DNA sequence in a sample. The process involves repeated cycles of DNA denaturation, primer annealing, and DNA extension. In each cycle, the target DNA is exponentially amplified. The key to detecting gene expression lies in the real-time monitoring of the amplification process.
During qPCR, fluorescent dyes or probes are incorporated into the reaction mix. These probes emit fluorescence when bound to the amplified DNA. As the PCR progresses, the amount of fluorescence increases proportionally to the accumulation of amplified DNA. The real-time nature of qPCR allows scientists to measure the fluorescence at the end of each cycle, providing a dynamic view of DNA amplification.
The cycle threshold (Ct) is a crucial parameter in qPCR analysis. It represents the cycle number at which the fluorescence signal crosses a predefined threshold. The Ct value is inversely proportional to the initial amount of target DNA—the lower the Ct, the higher the initial DNA concentration. By comparing Ct values of experimental and control samples, researchers can quantify the relative expression of a gene. This method provides a precise and quantitative measure of gene expression levels, making qPCR a valuable tool in molecular biology research.