1 The idea of "junk DNA" is also based on the assumption that most genetic information is transacted via proteins, an assumption that dates back half a century to a time when the pioneers of molecular biology were studying bacteria, wherein most genes do indeed encode proteins. By contrast, protein coding sequences occupy only ~1.2% of the human genome.
When introns were discovered 30 years ago it was immediately and universally assumed that these vast tracts of nonprotein-coding sequences within genes are nonfunctional, despite the fact they are transcribed. Their presence was rationalized as the leftovers of the early evolution of genes.2 At the same time, the finding that much of the mammalian genome (45% in humans) is derived from transposons, which are thought to be mainly parasitic hitchhikers, led to the related concept of "selfish DNA."3,4 This reinforced the increasingly conventional view that the genomes of ...
