<prompt> Resistance to zidovudine develops due to-Mutations at reverse transcriptaseIncreased efflux of the drug from inside the cellIncreased metabolism of the drugDecreased zidovudine 5 triphosphate formation  <response>: Ans. is a i.e., Mutations at reverse transcriptase Resistance to Zidovudine occurs by point mutation which alters reverse transcriptase enzyme. In the past when AZT was used alone, 50 patients became nonresponsive to AZT within 1-2 years therapy due to growth of resistant mutants - KDT 