8.2 Methods to detect gene expression

Quantification of how much gene expression levels deviate from a baseline gives clues about which genes are actually important for, for instance, disease outcome or cell/tissue identity. The methods of detecting and quantifying gene expression have evolved from low-throughput methods such as the usage of a reporter gene with a fluorescent protein product to find out if a single gene is expressed at all, to high-throughput methods such as massively parallel RNA-sequencing that can profile -at single-nucleotide resolution- the abundance of tens of thousands of distinct transcripts encoded in the largest eukaryotic genomes.