How can I predict the percent qPCR signal due to contaminating DNA, for a given qPCR assay, and its matching NRT control?
FAQ ID -2688
Assuming 100% amplification efficiency, each step increase in Ct value represents a doubling in the amount of qPCR template. Therefore, evaluating the difference in Ct values between the qPCR assay, and its matching NRT control, leads to the following predictions:
| CtNRT - Ct+RT |
Fraction of gene expression signal due to contaminating DNA |
Percentage of gene expression signal due to contaminating DNA |
| 1 |
(1/21) = 1/2 |
50% |
| 2 |
(1/22) = 1/4 |
25% |
| 3 |
(1/23) = 1/8 |
13% |
| 4 |
(1/24) = 1/16 |
6% |
| 5 |
(1/25) = 1/32 |
3% |