Fig.37:
Combinations of the basic building blocks of DNA to form nucleotides. (P, phosphoric acid; D, deoxyribose) The four nucleotide bases are A, adenine; T, thymine; G, guanine; and C, cytosine. These four different types of nucleotides make up DNA.The first stage in the formation of DNA is the combination one molecule of phosphoric acid, one molecule of deoxyribose and one of four bases to form a nucleotide. Four separate nucleotides are thus formed one for each of four bases: deoxyadenylic, deoxythymidylic, deoxyguanylic, and deoxycytidylic acids. Figure 38 illustrates the chemical structure of adenylic acid and Fig. 37 illustrates simple symbols for all the four basic nucleotides that form DNA.
Fig.38:
Deoxyadenylic acid, one of the nucleotides that make up DNA.
The Nucleotides