Use of RNA-Seq to examine transcriptomes (a) An mRNA is isolated, transcribed to cDNA, fragmented into smaller pieces, and ligated to adapter oligonucleotides that provide targets for sequencing primers. Sequencing then follows, using one of the methods described in Section 7.2. (b) The number of times a sequence from a given gene or segment of a gene appears in a sequencing read (i.e., the number of reads containing all or part of that sequence) is plotted. The number of reads from a given genomic region reflects the relative level of mRNA produced from that region. Shown here are data for a small portion of human chromosome 11, segment q13.4.