Control genes in quantitative molecular biological techniques: the variability of invariance

The measurement of transcript levels constitutes the foundation of today's molecular genetics. Independent of the techniques used, quantifications are generally normalised using invariant control genes to account for sample h andling, loading and experimental variation. All of the widely used control genes are evaluated, dissecting different methodological approaches and is sues regarding the experimental context (e.g. development and tissue type). Furthermore, the major sources of error are highlighted when applying thes e techniques. Finally, different approaches undertaken to assess the invari ance of control genes are critically analysed to generate a procedure that will help to discern the best control for novel experiments. (C) 2001 Elsev ier Science Inc. All rights reserved.