BRAINCAKEPositive ssRNA Viruses
In positive-sense single-stranded RNA (+ssRNA) viruses, the genome has the same base sequence as mRNA. As soon as it is uncoated inside the host cell, it can act directly as mRNA and be translated by host ribosomes.
The stages of replication are:
1. Attachment and entry: the virus binds to receptors and enters the cell; the RNA is released into the cytoplasm.
2. Translation: host ribosomes translate the viral RNA, often into one long polyprotein that is cut into separate proteins, including RNA replicase (RNA-dependent RNA polymerase).
3. Making a template: RNA replicase uses the + strand as a template to make a complementary negative (−) strand.
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Key terms in this lesson
- polyprotein
- A single long protein, translated as one chain from viral mRNA, that is later cut into several separate functional proteins.
More in Prokaryotic Cells
- Virus Life Cycle
- DNA Virus Latency
- DNA Virus Lytic Pathway
- RNA Virus Replication
- Negative ssRNA Viruses
- Retrovirus Replication
- Viruses and Disease
- The Spread of Viral Diseases
All 31 lessons in Prokaryotic Cells · All Edexcel AS-level Biology topics