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All 8 Flashcards — Diversity of structure in viruses
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Question
What is a retrovirus?
Answer
An **enveloped RNA virus** that carries the enzyme **reverse transcriptase**. HIV is the classic example.
Question
What does reverse transcriptase do?
Answer
It makes a **DNA copy from an RNA template** (RNA → DNA) — the **reverse** of normal transcription (which goes DNA → RNA).
Question
Why is it called 'reverse' transcription?
Answer
Normal transcription goes **DNA → RNA**; reverse transcription goes **RNA → DNA** — the opposite direction.
Question
What is a provirus?
Answer
The **viral DNA after it has integrated** into the host cell's own DNA. The host then transcribes it to make new virus.
Question
Which cells does HIV infect, and what does destroying them cause?
Answer
HIV infects **helper T-lymphocytes (CD4 cells)**. Destroying them weakens the immune system, causing **AIDS**.
Question
Why does HIV mutate so quickly?
Answer
**Reverse transcriptase has no proofreading**, so its copying errors are not corrected — giving a **high mutation rate** and rapid evolution.
Question
Why is HIV hard to treat and to vaccinate against?
Answer
Its fast mutation lets it **evolve drug resistance** (so combination antiretrovirals are used) and **escape the immune system** (so no effective vaccine yet).
Question
Why is reverse transcriptase a good drug target?
Answer
It is an enzyme **your own cells don't have**, so blocking it stops the virus copying its RNA into DNA while largely sparing your cells.
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Full study notes for Diversity of structure in viruses
Topic 1.5 hub
Viruses
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