Standardized amplification curves made with serial dilutions of recipient/donor DNA.

Artificial chimeric DNA samples were made with serial dilutions of recipient DNA in donor DNA (14 serial halved dilutions from 100% to 0.01% of recipient DNA in a total amount of 250 ng chimeric DNA). (A) ABI PRISM 7700 recipient-specific marker ΔRn curves for the 14 chimeric DNA samples. Regular positive amplification curves are observed until 0.01% recipient DNA dilution, and ΔRn curves shift to the right as recipient DNA fraction decreased. By contrast, no amplification occurred with the donor DNA (0% recipient DNA, used as a negative control for recipient-specific marker amplification). (B) The recipient marker standardized amplification curve plotted from these results: recipient marker Ct values correlated linearly with the logarithm of recipient/donor DNA fraction (r = 0.995). PCR efficiency derived from the slope of the curve was E = 0.97 for this assay.