Viruses Flashcards
What are the general properties of viruses
Small,
made of nucleic acid genome surrounded by capsid
Facultative lipid membrane
Obligatory parasites
What are capsids made of
Proteins called capsomers
How are capsids assembled
Self assembled and highly ordered
Icosahedral or helical
What is the nuclear envelope made of
Lipid bilayer with glycoproteins from host or virus
What is the role of the envelope
Allows entry into host cell via fusion/ endocytosis
What do bacteriophages contain
Mix of icosahedral/filamentous structures
What group of viruses is DNA
1,2 and 7
What group of viruses is RNA
3,4,5,6
How do class 1 viruses divide?
Semiconservative replication
How do class 2 viruses divide?
Semiconservative but discard - strand
How do class 7 viruses divide?
Transcription followed by reverse transcription
How do class 3 viruses divide?
Transcription of minus strand
How do class 4 viruses divide?
Used directly as mRNA virus
How do class 5 viruses divide?
Transcription of minus strand
How do class 6 viruses divide?
Reverse transcription –> dsDNA intermediate –> transcription of - strand of mRNA
Why do we use the Baltimore classficiation
Takes into account the nature of the genome (RNA/DNA)
The type of RNA/DNA
The genome replication mechanism
What are the 5 stages in the life cycle of viruses
Attachment, Genome injection, Production of Nucleic acid and proteins, Maturation and release
What are the 2 types of bacteriophages
Virulent phages and temperate phages
What is an example of a type 1-7 virus
Type 1: Herpes, Poxvuris, adenovirus and papillomavirus
Type 2: Adeno-associated virus
Type 3: Reovirus
Type 4: Togavirus, poliovirus, foot and mouth disease virus and Hepatitis (A and C)
Type 5: Influenza
Type 6: HIV
Type 7: Hepatis B virus
What is the difference between virulent and temperature bacteriophages
Virulent kill bacteria during every infection cycle since they replicate only via the lytic cycle
Temperature phages don’t kill bacteria immediately after the infection since they replicate using both lytic and lysogenic cycles
What is the difference between lytic and lysogenic cycle
Lytic cycle involves reproduction of viruses using a host cell to manufacture more viruses, which burst out of the cell
Lysogenic cycle involve the incorporation of the viral genome into the host cell genome, infecting from within
What is the difference between RNA and DNA viruses
DNA replication takes place in the nucleus whereas RNA replication takes place in the cytoplasm
DNA viruses are stable whereas RNA viruses are unstable
Which virus (DNA or RNA) is harder to make a vaccine for
RNA, because of the lack of proof reading RNA viruses mutate at a higher rate
Is the genome of a viruse surrounded by a capsule
No
Can the capsid contain polysaccharides
No
Why is the genome of a virus small
Because they hijack host machineries to multiply
What factors are taken into account by Baltimore classification
Mode of replication
Type of nucleic acids in the genome
What does the nucleocapsid always contain
Nucleic acids
What do bacteriophages only infect
Bacteria
When does the genome of temperate bacteriophages replicate
As the host genome replicates
What does the life cycle of viruses require the production of
Positive strand of RNA
What is the correct order of a viruses lifecycle
Attachment, genome injection, production of nuclei acids and proteins, assembly of virions and release
What is a virion
the complete, infective form of a virus outside a host cell, with a core of RNA and a capsid.
