This animation illustrates a proposal to replace the nucleic bases letter representation with five discrete values on the gray scale. Instead of letters UCAGT this concept employs five discrete values U=Black, C= Dark, A=Gray, G=light, and T= White. Value of "black" is defined as "absence of light", thus U =100% black, C=75% black, A=50%black, G=25% black, T=0% black. This is a linear structure with two elements U and T having one neighbor, while three elements, C, A, and G are with two neighbors. The difference between neighboring values is 25%.
If we define all pairs that differ 50% we will get: U-A, C-G, A-T. With this single rule we have established all the base pairs for both DNA and RNA and the exchange value which defines these relationships is the value of Gray that represents Adenine (A).