Questions and Answers
What type of virus is a retrovirus?
How does the retrovirus HIV enter the cell?
What is the function of the protein reverse transcriptase?
What is the product of reverse transcription?
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What is the direction of reading during reverse transcription?
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What is the purpose of the uncoating step in retroviral replication?
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How many special proteins are carried by the retrovirus inside its envelope?
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What is the name of the final product of reverse transcription?
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What is the purpose of integrase in the HIV replication cycle?
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What happens to the RNA strand after integrase clips off the 3' ends?
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What is the term for the integrated viral DNA in the host genome?
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What is the function of the protease in the HIV replication cycle?
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What is unique about the provirus stage compared to the regular lysogenic cycle?
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What happens to the viral mRNA after it exits the nucleus?
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What is the term for the viruses that have not yet matured and are still missing their envelope?
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What happens to the immature viruses before they infect other cells?
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What is the purpose of the retrovirus replication cycle?
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What is unique about the HIV replication cycle compared to traditional replication?
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Study Notes
Retroviruses
- Retroviruses are a special case of viruses that don't fit into the lytic or lysogenic categories.
- They are enveloped, single-stranded RNA viruses that carry three special proteins.
Entry into the Cell
- Retroviruses enter the cell through direct fusion.
- After entry, the nucleocapsid undergoes uncoating, releasing the proteins and RNA.
Reverse Transcription
- The red protein, reverse transcriptase, reads the RNA from 5' to 3' end and forms complementary DNA (cDNA).
- Reverse transcriptase works again on the RNA to make another cDNA strand, which recombines with the first cDNA strand to form a double-stranded DNA.
Integration
- The blue protein, integrase, clips off the 3' ends of the DNA strands, forming sticky ends.
- Integrase integrates the viral DNA into the host's DNA.
- The viral DNA is now part of the host's genome, known as the provirus stage.
Transcription and Translation
- The host cell transcribes the viral DNA into viral mRNA, which exits the nucleus.
- The viral mRNA is translated into proteins, including the capsid proteins, reverse transcriptase, integrase, and protease.
Assembly and Budding
- The newly formed proteins and RNA self-assemble into new viruses, minus the envelope.
- These immature viruses bud off from the host cell, taking a piece of the membrane with them.
- The resulting viruses are still immature and require maturation.
Maturation
- The green protein, protease, cleaves the proteins to make them fully functional.
- This maturation process occurs before the virus infects another cell and starts the replication cycle again.
Retrovirus Replication
- Retrovirus replication is a unique process that combines elements of both lysogenic and lytic cycles.
- It involves reverse transcription, integration, transcription, translation, assembly, budding, and maturation.
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Description
Explore the special case of viral replication, retroviruses, and learn about their distinct features that set them apart from other viruses.