Work

The substances known as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are found in nearly all cells in almost all organisms. The building blocks of DNA and RNA consist of nucleotides. In turn, these consist of what scientists call a nitrogen base, a sugar molecule, and one or more phosphate groups. Around 1940, Alexander Todd began to examine the composition of nucleotides more closely. Using chemical methods, he split nucleotides apart and compared their parts with substances that had been constructed from known components in a way that was already understood.