This document analyzes RNA-seq data from 16 human tissues and 5 cell lines to investigate whether genes typically express multiple isoforms at similar levels or have a single dominant transcript. The analysis found that: 1) For around 79% of genes, one isoform is expressed at least twice as strongly as the next highest isoform. 2) The major transcript of a gene tends to be consistently highly expressed across different tissues, though some switches between dominant transcripts were observed. 3) Around 85% of all mRNA comes from these dominant transcripts. This suggests that despite transcriptome complexity, the traditional view of one gene producing one protein may be closer to the truth than previously believed.