1. The nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are polymers of nucleotide units 1.1 DNA consists of four kinds of deoxyribonucleotide units linked together through covalent bonds 1.1.1 Each nucleotide unit is made of a nitrogenous base (the various part in the four different deoxyribonucleotides), a pentose sugar and a phosphate group