Final answer:
Real-time PCR (quantitative PCR or qPCR) is the type of PCR that permits absolute quantification of nucleic acids by using fluorescence to monitor DNA amplification in real time.
Step-by-step explanation:
The type of PCR that results in absolute quantification is known as real-time PCR (quantitative PCR, or qPCR). This advanced PCR technique involves the use of fluorescence to monitor the increase in double-stranded template DNA as the PCR reaction occurs in real-time.
By quantifying the fluorescence at each cycle, qPCR allows for the estimation of the original amount of the nucleic acid sequence present in a sample, yielding not just the presence of specific transcripts, but also their relative quantities.
Applications of qPCR are diverse and include studies of differential gene expression, gene regulation, and forensic science. The technology requires precise primers and a fluorescent dye that is specific to double-stranded DNA. The fewer amplification cycles needed to achieve a detectable level of fluorescence, the greater the initial concentration of the target nucleic acid in the sample. This principle is key for quantifying levels of gene expression.