Able to see correct product with 2 rounds of PCR, but my PI doesn't want me - How do I convince her that "2 rounds of PCR is OKAY?" (Apr/19/2011 )

So after 1 round of PCR, I cannot see a product with my primers. With 2 rounds, I am able to. However, my PI doesnt want me to do this because it introduces "contamination". I'm working with human samples. (limited amounts of DNA)

Can you help me convince her?

What PCR are you doing: MSP or BSP? For either, two rounds or nested PCR are OK. In MSP, you can first amplify the converted DNA using a pair of universal primers and then reamplify using M or U primers. For BSP, two rounds of PCR are needed for most of the times.