Lecture 35. Virus Replication II Flashcards
What do many viruses go against ?
Central dogma
How large is varicella zoster virus ?
125kb - 70 proteins
Where does transcription and replication of the varicella zoster virus occur ?
The nucleus
What does transcription of varicella zoster virus require ?
Host RNA polymerase II
What does viral polymerase synthesis of varicella zoster virus do ?
Create new copies of DNA genome
What are the eight steps of varicella zoster virus replication cycle ?
- Attachment and entry
- Transport to nucleus
- Genome replication and transcription
- mRNA translation and protein synthesis
- Capsid formation and genome packaging
- Capsid buds through nuclear membrane
- Virion matures by budding through the trans golgi network
- Vesicle and plasma membrane fuse, releasing virion
What size is the poliovirus ?
8kb - 11 proteins
When is mRNA translated in poliovirus ?
Immediately after infectious
What part of poliovirus is infectious ?
The genome alone
What does mRNA and genome synthesis use for poliovirus genome replication ?
Viral RNA dependent RNA polymerase
Where does genome replication occur in poliovirus ?
Cytoplasm
What is the poliovirus replication cycle ?
- Attachment and entry
- Genome and mRNA translation
- Polyprotein processing
- Genome synthesis
- Assembly
- Egress upon cell lysis
What does the positive sense single stranded RNA genome look like in poliovirus replication ?
mRNA
What is poliovirus translated into and by what ?
- Polyprotein
2. Host ribosomes
What does viral polymerase synthesis in poliovirus replication ?
New copies of RNA genome
What does the positive sense single stranded RNA act as in Covid ?
mRNA
What is subgenomic mRNA synthesised from in Covid ?
Replicated genome
Where does Covid replication occur ?
Cytoplasm
What is the covid genome directly translated into ?
Two different polyproteins
What is the covid genome directly translated by ?
Host ribosomes
What do viral polymerase synthesis in covid ?
Subgenomic mRNAs from replicated negative sense genome intermediate RNA
What size is influenza virus ?
13 kb - 12 proteins
How many segments does the influenza virus genome have ?
8
Where does transcription and translation of influenza occur ?
Nucleus
What are the six steps in influenza replication cycle ?
- Attachment and entry
- Genome segments transported to nucleus
- mRNA synthesis by virion polymerase
- Protein synthesis
- Genome replication by viral polymerase
- Assembly and budding
Where does mRNA synthesis and genome replication occur in influenza virus replication ?
Nucleus
What are the negative sense single stranded RNA converted into by mRNA in influenza replication ?
Virion polymerase
What effect does the segmented genome of influenza virus have on genetic diversity ?
- Lots of potential for mixing genes
2. Lots of genetic diversity
What is genetic reassortment ?
The mixing of genes between two organisms to make a new genetic sequence
What is an antigenic shift ?
The complete replacement of the HA or NA with a novel HA or NA.
What do new influenza viruses cause ?
Pandemics
What size is the HIV genome ?
9kb - 16 proteins
What does the HIV genome have ?
Two identical copies of the positive sense single stranded RNA
What are the seven steps in the HIV replication cycle ?
- Attachment and entry
- Reverse transcription and DNA synthesis
- Virion integrates pro-viral genome into host DNA
- Host RNA polymerase II generates new viral RNA (mRNA and genome)
- mRNA translated into 3 polyproteins
- Protein processing by host and viral enzymes
- Assembly and budding
What is the positive sense single stranded RNA genome copied into in HIV ?
Double stranded DNA
What is positive sense single stranded RNA genome copied into double stranded DNA by in HIV ?
Virion reverse transcriptase
Where is HIV replicated in ?
Cytoplasm
What does virion integrase incorporate into host DNA in nucleus in HIV ?
Pro viral genome
What do DNA polymerases have ?
Proofreading ability
What do virus RNA polymerases lack ?
Proofreading capability
What does too much error create ?
Unviable or dead virus particles
Why are there two identical copies of viral genome in HIV ?
- Parts of both genomes can be used as templates during reverse transcription
- Genetic recombination can patch together one complete DNA copy from two damaged RNA genomes
How are new virus released from the cell ?
- Lysis
2. Budding