Text as nucleotides
Two bits, four bases. Each character becomes its 8-bit binary form, and each pair of bits picks a nucleotide:
00→ A (adenine)01→ G (guanine)10→ C (cytosine)11→ T (thymine)
So every character is four bases, and A— binary01000001 — comes out as G-A-A-G. The mapping is reversible: paste a sequence into the right-hand pane and it reads back.
The helix beside it is drawn from whatever you typed, with the base pairs real DNA would use — A with T, C with G. It is a conceit, not biology: nothing here would survive contact with a ribosome.