The genetic information of a cell is stored in molecules of deoxyribonucleic acid (DNA). The DNA, in turn, passes its genetic instructions to ribonucleic acid (RNA) for directing various metabolic activities of the cell.
DNA is a polymer of nucleotides (Figure 7 DNA molecule consists of three parts—a nitrogenous base, a five‐carbon sugar called deoxyribose, and a phosphate group. There are four DNA nucleotides, each with one of the four nitrogenous bases (adenine, thymine, cytosine, and guanine). The first letter of each of these four bases is often used to symbolize the respective nucleotide (A for adenine nucleotide, for example).
Figure 7. The molecular structure of nucleotides.