Illuminating the Genome’s Dark Matter TheDeeperGenome:WhyThere IsMore to theHumanGenome Than Meets the Eye

John Parrington’s book The Deeper Genome provides us with a closer look at the enigma of junk DNA. Often referred to as the dark matter of the genome, junk DNA is an important but often overlooked part of the human genome. (Perhaps, in light of recent discoveries, this term might be somewhat problematic; however, it is the term that Parrington uses and we will follow that here.) The dark matter metaphor is particularly apt: akin to the great expanses of dark matter within our universe, junk DNAmakes up the vast majority of the genome. And just like dark matter, whose properties can only be inferred from its effects on observable matter, much of our junk DNA can only currently be characterized by its regulatory effects on the smaller fraction of coding DNA. Further, just like dark matter is presumed to account for discrepancies in our understanding of the universe— between what’s theoretically predicted versus actually observed—junk DNA is thought to account for the majority of associations with genetic diseases found by genome-wide association studies (GWAS). Insofar as this is the case, junk DNA is medically relevant and contains actionable information. Finally, just like dark matter contains historical evidence of events from the primordial universe, junk DNA, lacking the evolutionary pressures on protein-coding genes, contains vestigial information relating to themolecular history of our species. The Deeper Genome is unique in that it provides an entertaining tale of personalities with lots of useful technical knowledge. We highly recommend the book as a supplement for classroom teaching as it covers fundamental concepts in an easily readable format. Students will likely find it even more interesting than many of the more standard textbooks. For example, the book goes through the classic story of the double helix, starting all the way from Aristotle and eventually working its way through Darwin, Wallace, Mendel, and Morgan to more contemporary times, with Gilbert and Sanger. To wit, Parrington ably describes how early abstractions related to genetic inheritance were concretized over time and culminates in quite readable descriptions of current scientific research and experimentation. He provides lucid textual descriptions of the canonical theory of Darwinian evolution and its synthesis with the work of Mendel by Fisher and others. He even covers a somewhat forgotten alternative theory: the pre-Darwinian Lamarckian evolutionary theory and its recent resurgence—e.g., in Eugene Koonin’s twostroke process, with an initial Lamarckian epigenetics phase and a subsequent Darwinian selection phase. Finally, the