Ct value

This article describes a size of an exponential growth phase in the polymerase chain reaction (PCR). For the CT number or computed tomography (CT) CT value, see the Hounsfield scale

The Ct value , abbreviated for English. threshold cycle is a theoretical quantity that describes the beginning of the exponential growth of a curve. The size is particularly important for the quantification of DNA molecules during a real-time quantitative PCR . Here the Ct value describes the part of the curve in which the fluorescence rises exponentially above the background value for the first time.

The more deoxyribonucleic acid that was present in the sample solution before the polymerase chain reaction (PCR), the more copies are created in the polymerization cycles and the faster the fluorescence signals and, accordingly, the more likely the fluorescence to exceed the threshold value. A comparison of the Ct value of two samples shows which one contained more DNA before the amplification , provided that both amplifications were carried out with the same efficiency.

literature

• Ulrich Kück: Internship in molecular genetics. Springer, doi : 10.1007 / 3-540-26469-8_4