DNA has the nitrogenous base, phosphate, and sugar. The nitrogenous bases are purines and pyrimidines. The purines are adenine and guanine. The pyrimidines are thymine and cytosine. The purines are double ring structure while the pyrimidines are the single ring made up of carbon and nitrogen. Purines pair with the pyrimidines by hydrogen bonds. It has deoxyribose sugar which has hydrogen at second carbon. The sugar is linked to nitrogenous base at the first carbon by the glycosidic bond. DNA is the chain of polynucleotide which are joined by the phosphodiester bonds.