In real-time PCR (qPCR), target gene expression levels are often normalized to the expression of a reference gene to obtain relative quantification of expression. This normalization strategy corrects for differences in the amount of input RNA and variations in reaction efficiency. A housekeeping gene whose expression level is stable in the samples being tested is commonly used as the reference. However, in some experimental systems, it may be difficult to identify a gene with stable expression. In such cases, an external standard RNA can be added to the reaction to serve as a reference.
External Standard Kit (λ polyA) for qPCR provides an external reference for qPCR normalization. The kit contains the reference RNA (λ polyA+ RNA-A) and primers for real-time PCR detection. To use, a fixed amount of the λ polyA RNA can be directly added to RNA samples before cDNA synthesis with oligo-dT. Subsequently, SYBR Green-based qPCR detection can be used to quantify the amount of λ polyA RNA in each sample.