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Seventeen years ago, the completion of the Human Genome Project revealed that there are around 20,000 protein-coding genes in the human genome—a puzzling result, given our intricate biology. Thanks to the advancement of large-scale proteomic studies over the decade following that milestone, researchers realized that some human cells contain billions of different polypeptides. Researchers realized that each gene can encode an array of proteins. The process of alternative splicing, which had first been observed 26 years before the Human Genome Project was finished, allows a cell to generate different RNAs, and ultimately different proteins, from the same gene. Since its discovery, it has become clear that alternative splicing is common and that the phenomenon helps explain how limited numbers of genes can encode organisms of staggering complexity. While fewer than 40 percent of the genes in a fruit fly undergo alternative splicing, more than 90 ...
