Biochemists have long recognized that the nucleotide sequences comprising DNA molecules encode digital information. The nucleotide sequences represent a succession of discrete units (i.e., genetic letters), just like the 1’s and 0’s that encode the digital information on a CD or in an MP3 file. In this framework, a gene consists of an isolated piece of code specifying the digital information (i.e., amino acid sequence) used by the cell’s machinery to build a particular protein.
The cell doesn’t need every protein encoded in its genome all the time. Sometimes genes are expressed (and the corresponding proteins are produced), and other times they aren’t. That is, the digital information in a gene can be expressed or not. To say it another way, the gene is a discontinuous entity that adheres to the “on-off” logic characteristic of digital information.
What hasn’t been apparent to biochemists is the analog information harbored in DNA—at least until Muskhelishvili and Travers reported it.2 They note that the nucleotide sequences of DNA not only encode information to make proteins, these sequences also impact the higher order architecture of DNA, which houses the analog information.
Most people recognize DNA’s iconic double helical structure, but what may not be well known is that the DNA double helix can adopt a variety of higher order shapes. One of the most prevalent architectures is referred to as a supercoil. The image below depicts the supercoiling of a typical bacterial genome. (In bacteria, the ends of the double helix link together to form a circular piece of DNA.)