Nucleic acids are made up of monomers called nucleotides. Each nucleotide consists of a five-carbon sugar, a phosphate group and a nitrogenous base. Repeating nucleotides create nucleic acids such as DNA, or deoxyribonucleic acid, and RNA, or ribonucleic acid.
Nucleic acids consist of a backbone of sugar alternating with a phosphate group; this backbone is bonded to the nitrogenous base. The five-carbon sugar can be deoxyribose as in DNA or ribose as in RNA. Four nitrogenous bases are found in DNA and four are in RNA. Nitrogenous bases can be divided into two groups: purines and pyrimidines. Purines consist of adenine and guanine. Pyrimidines include cytosine, thymine and uracil. Adenine and guanine are found in both DNA and RNA; however, DNA contains the pyrimidines cytosine and thymine, whereas RNA uses cytosine and uracil.