ABSTRACT
Most genomes, including the human genome and those of all other cellular life forms, are made of deoxyribonucleic acid (DNA), but a few viruses have ribonucleic acid (RNA) genomes. The fact that genes are made of DNA is so well known today that it can be difficult to appreciate that for the first 75 years after its discovery the true role of DNA was unsuspected. The errors in understanding DNA structure lingered on, but by the late 1930s it had become accepted that DNA, like protein, has immense variability. In the years before 1950, various lines of evidence had shown that cellular Proteins are functionally diverse because the amino acids from which proteins are made are themselves chemically diverse. The biological information encoded by the genome finds its final expression in a protein whose biological properties are determined by its folded structure and by the spatial arrangement of chemical groups on its surface.
