2.1. Introduction

The initial processing of a sample is another key step in ensuring the uniformity and reliability of an assay. Nevertheless, generally little attention is paid to optimizing this part of the protocol for both maximum recovery of the target molecule(s) and for reducing variability. In general, the shorter and faster the protocol the better, since each additional step will contribute to the overall error and reduce the recovery efficiency, both of which compromise results. Here we will describe generalities of sample processing before independent chapters describing RNA and DNA extraction from samples.