The monomeric deoxynucleotides in DNA are held together by 3′-5′-phosphodiester bond. DNA structure is often represented in a shorthand form as shown in Figure 5.2. A DNA molecule is made of two chains of several thousands of linked nucleotides. Each nucleotide consists of a phosphate group, a pentose (= a sugar with five carbon atoms and a base containing nitrogen (adenine, thymine, guanine and cytosine).

Figure 5.2 Shorthand Form of the Structure of DNA