Is there an easy way to manipulate the amount of DNA in the blood cells so the reference blood would have the same amount of housekeeping genes but difference amount of target genes?

In order to develop a diagnostic assays that can identify the target gene in the blood, we need to make the reference blood samples with difference amount of the target genes but same amount of the housekeeping reference genes. However, we cannot just add DNA into the blood because it will be washed away in the DNA extraction process. Is there an easy way to insert the genes into the blood cells?