RNA (Ribonucleic acid) was a nucleic acid.
The Vrall on the Moon created miniature RNA spores encoded with the construction information for a space engine, which they fired towards Earth with a vacuum gun. Eventually, one spore struck the mind of a Professor Boyes-Dennison, who developed the engine with the aid of his twenty-two year old daughter Emily. (PROSE: Imperial Moon)
A swamp monster that landed on the planet Sunday could create a protein-RNA mix to control smaller animals, such as the Sundayan otters; this mix implanted memories and images into them and generally led to a rise in aggression. (PROSE: Wetworld)
One explanation the Fourth Doctor offered for the Fendahl's influence on humanity was that it "fed into the RNA of certain individuals the instincts and compulsions necessary to recreate. These were fed through the generations till they reached Fendelman and people like him." It could, however, just be coincidence, he added. (TV: Image of the Fendahl)