Chapter 19 Flashcards
What did Beijerinck conclude?
That it needed host to reproduce
What are the 2/3 parts of viruses?
- Genome
- Capsid
- Envelope
What are the components of a viral envelope and where do they originate from?
Membrane proteins/phospholipids from host cell;
Proteins and glycoproteins of viral origin
What are bacteriophages?
Viruses that infect bacteria strictly
What does Phage T4 infect?
E. Coli
Host range?
Range of types of cells a certain type of virus can infect
When does viral infection begin?
When virus binds to host cell
What are the 3 mechanisms of genome entry?
- Injection from tail
- Endocytosis
- Fusion of envelopes
What is the method of genome entry for phages?
Injection from tail
What are capsids made up of?
Capsomeres
What type of phage undergoes the lytic cycle?
Virulent phage
What type of phage undergoes lysogenic and lytic cycle?
Temperate phage
Why haven’t phages exterminated all bacterium
- Natural selection
- Restriction enzymes
- Lysogenic cycle
What do restriction enzymes do?
Identify foreign DNA and cut it up
What joins the prophage and host cell’s genome together?
Viral proteins
Prophage?
Phage DNA segment in bacteria DNA
What triggers lytic mode from lysogenic mode?
Environmental signals (chemical, radiation)
How is transcription of prophage genes prevented
Protein coded by prophage prevents its transcription
What do nearly all animal viruses have?
Membrane and RNA
What are glycoproteins made by?
Ribosomes bound to ER
What are the 2 ways of creating a viral envelope?
- Exocytosis; glycoproteins use host cell membrane
2. Host envelope replaced by Golgi apparatus membrane
What are the three types of RNA genomes found in animal viruses?
- Directly as mRNA
- Template for mRNA to be transcribed from
- Retroviruses
In retroviruses, what transcribes the RNA to DNA?
Reverse transcriptase
HIV contains what?
2 RNA molecules and 2 reverse transcriptase
Provirus
DNA (transcribed from RNA) incorporated into host’s genome
What can the RNA transcribed from a proviral DNA strand do?
- Serve as mRNA for viral protein synthesis
2. Serve as genome for new viruses
What are the 2 DNA molecules viruses are like
Plasmids and transposons
What do plasmids do?
They work apart from cell’s genome and can tranfer between cells
What do transposons do?
DNA segments that can move within cell’s genome
Difference between provirus and prophage?
Provirus stays permanently in host’s genome, prophage can turn lytic
