Describe the three basic components of nucleic acid nucleotides, drawing comparisons and contrasts between the nucleotides of DNA and those of RNA.
The two types of nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are composed of building-block molecules called nucleotides. Each nucleotide has three parts: a phosphate group and a nitrogenous base both covalently bonded to a five-carbon sugar. DNA has four types of nucleotides, each with deoxyribose as its sugar but with differing nitrogenous bases. The purine bases adenine and guanine have double-ring structures; the pyrimidine bases cytosine and thymine have single-ring structures. RNA nucleotides differ from DNA nucleotides in two important ways: RNA has ribose as its sugar, and RNA does not contain thymine but, instead, contains a related pyrimidine base, called uracil.
