The Biology Project: Immunology

HIV and AIDS Problem Set

Problem 5: AZT, a reverse transcription inhibitor

Tutorial to help answer the question

AZT, a reverse transcription inhibitor, stops HIV reproduction at what stage?

A. Producing viral DNA from RNA
B. Translating RNA into protein
C. Producing viral and host DNA from RNA
D. Integrating viral DNA into host DNA


The HIV lifecycle is divided into six stages:

Graphic © James A. Sullivan. Used with permission

1. Viral attachment to Helper T cell

Reverse transcription of viral RNA to form DNA

3. Integration and transcription of viral DNA
4. Translation of viral DNA
5. Viral protease enzyme activation
6. Assembly and budding to form new virus.

Reverse transcription is the second stage of the HIV lifecycle. HIV is unusual because it has RNA as its genetic material, not DNA like most viruses and cells. HIV undergoes reverse transcription to convert its genetic material (RNA) into a form compatible with its host's genetic material (DNA).

Graphic © James A. Sullivan. Used with permission

Reverse transcription inhibitors (RTIs) were the first drugs available to treat HIV. RTIs block reverse transcription.

Graphic © James A. Sullivan. Used with permission


If reverse transcription proceeds unhindered, the viral DNA produced integrates with host DNA and the cell produces both normal and viral proteins. Next the viral protein is cut by the protease enzyme, smaller proteins are assembled, and new copies of HIV are released.

View animations of the HIV lifecycle and descriptions of drug actions, courtesy of CellsAlive


The Biology Project
The University of Arizona
Monday, April 3, 2000
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