PCR internal control - how does it work? (Jan/17/2006 )

Confused, new-to-mol.bio. person here. I've been given the task of incorporating a PCR internal control into our assay, specifically, GAPDH. Basic question here: How does the internal control work? Is there a website that can explain this in layman's terms? Please forgive my ignorance. Thank you in advance.

The internal control is used to verify identical sample loading in each assay. When there are many separate PCR reactions that will eventually be comapared to each other on a gel, it helps to know (via an internal control or otherwise) that each reaction used the same amount of starting material.

Since you're planning to use GAPDH as a control, I'm assuming you intend to run RT-PCR. In this case the GAPDH RNA levels are maintained by the cell and can thus be used as a PCR control. One would expect to see no variation in the GAPDH amplicon.