The 10 gene sets were ordered by increasing levels of expression, with the first level corresponding to genes with the lowest expression and the tenth level to genes most highly expressed. Because these gene sets exhibit a consistent expression pattern, they can be used to adjust the data for non-biological variation. Importantly, in addition to being useful for data normalization, the invariant genes provide a simple quality check in real time as detection occurs, which is valuable in a high-throughput process.
