Animation: Mechanisms of NRTI Resistance (Nucleoside Analogue Discrimination)A mechanism that allows HIV to become resistant to NRTI therapy is known as nucleoside analogue discrimination. This animation describes how mutated viral reverse transcriptase enzyme can discriminate against the incorporation of many types of NRTI nucleoside analogues during the construction of viral DNA, while allowing the incorporation of naturally-occurring nucleosides. This permits the continued synthesis of viral DNA, thus contributing to HIV resistance.