Methods and control compositions for a quantitative polymerase chain reaction

A qPCR control composition, said control composition comprising i) a first nucleic acid construct comprising at least one barcode sequence fragment and at least one GC content fragment, wherein the first nucleic acid construct further comprises at least a first and a second primer binding site fragment, and ii) a second nucleic acid construct comprising the same barcode sequence fragment as in the first nucleic acid construct and at least one GC content fragment with a different percent GC content than the GC content fragment in the first nucleic acid construct, wherein the second nucleic acid construct further comprises at least a first and a second primer binding site fragment.