Fig. 1
From: Hydroxymethylbilane synthase (HMBS) gene-based endogenous internal control for avian species

Exogenous and endogenous internal controls in molecular diagnostics. An exogenous IC is introduced into a test sample to monitor the efficiency of DNA extraction and PCR. In comparison, the endogenous internal control which is the reference genes of animal hosts and is present in the test sample can be used to monitor any potentials problems from sample collection and PCR during molecular diagnostics