Week8C1-C2 : Taxonomy viruses Flashcards
Viruses are grouped into families that end with ____
viridae
Virueses are given a genus name that end with ___
virus
Viruses are given a species name that is in ____
english
The ____ configuration of RNA genome can be translated directly
plus
The minus strand ssRNA genome needs to be ___ before it can be translated
transcribed
How many classes is there in the baltimore classification scheme
7 classes
The baltimore classification scheme is a classification based on ____
type of genome
what are the steps in the life cycle of a virus?
- adsorption
- penetration
- uncoating
- replication
- maturation
- release
What is viropexis ?
the endocytosis of a virus by the host cell
What are the three ways viruses can enter the host cell?
- direct penetration (everything left outside)
- membrane fusion (enveloped viruses, the envelope is left at surface)
- viropexis (most enveloped viruses of eukaryote, eveything enters)
T or F : in enveloped viruses, the capsid may be left at the surface
false, the capsid is left at the surface only for naked viruses
The lamba and T4 have a ____ genome
double stranded DNA
The øX174 has a _____ genome
single-stranded DNA genome (+)
The MS2 has a _____ genome
single stranded RNA genome (+)
What are the two periods of virus replication
- latent period
2. release (rise) period
What are the two stages of the latent period ?
- eclipse
2. maturation
What is the burst size?
number of virions released
What is the eclipse?
time necessary for the host cells to replicated the viral genome and to synthesize the viral components
What is the maturation perido?
time needed for the different components to be assembled
The ø6 has a _____ genome
double stranded RNA genome
Most phages contain ____ genomes
dsDNA linear
What is a phage?
a viruse that attacks the bacteria
What are the two types of bacteriophages?
- virulent phages
2. temperate phages
_____ phages always leads to the lysis of host cells
virulent
____ phages have two options, ____ pathway or ___ pathway
temperate
lytic
lysogenic
Lamba is a ___ phage
temperate
the bacteriophage T4 recognize the ____ on the membrane
LPS
Bacteriophage T4 is a ___ phage
virulent
Viruse replication takes ___ minutes in the case of bacterial viruses
25-30
Viruse replication takes ___ hours in the case of animal viruses
8-40h
What is a lysogen ?
bacteria that contains a prophage
What is a prophage?
viral DNA incorporated into the host genome
where is intergrated the viral DNA in the bacrerial DNA
at the att-lambda site
What is the enzyme that catalyse the entry of the viral DNA into the bacterial host genome
lambda integrase
The region ____ is complementary to the cut region in the temperate phage genome
COS
What are the steps in the single-stranded DNA (+) phage infection
- the minus DNA strand must be synthesized
- From the - DNA strand, mRNA (+) is made and then translated
- Replication of the genome by rolling circle
- gives one replicative dsDNA form and one ssDNA (+) strand
- The dsDNA can make another replicative form
What are the steps in the single-stranded RNA (+) phage infection
- the + strand is used for translation to make viral proteins and RNA replicase
- RNA replicase (RNA dependant RNA polymerase) synthesize the - strand.
- The - strand is used to make more + strand ssRNA.
The genomes of ___ viruses will usually be replicated in the nucleus of the cell.
DNA viruses
The genomes of ___ viruses will usually be replicated in the cytoplasm of the cell.
RNA viruses
What are the steps in the double-stranded DNA phage infection
- the double stand is used to make mRNA
- The mRNA is used to make early, delayed and late proteins
- rolling circle replication produces new ds-DNA
What are the steps in the single-stranded DNA (+) phage infection in the case of polio?
- the + strand is used for the synthesis of a large polyprotein
- the large protein is cleaved into smaller proteins (structural proteins, proteases, RNA replicase)
- RNA replicase is used to make a - strand from the plus strand
- the - strand is used has a template to make more + strands
What is the purpose of the protease in the polio virus
cleave the large polyprotein
What are the steps in the single-stranded RNA (-) phage infection
- the - strand is first transcribed into a + strand by the RNA polymerase that comes inside the virus
- the + strand is used to make proteins and RNA polymerase
- The + strand is used to make more - strands
Measle is an example of ____ genome
minus ssRNA
Polio is an example of ___ genome
plus ssRNA
What are the steps in the double-stranded RNA phage infection
- the minus strand is used to make + strands
2. the + strand is translated to proteins and used to make more - strands
HIV is an example of ____ virus
retro
The virion of HIV carries :
- reverse transcriptase
- two copies of ssRNA (+)
- integrase
- proteases
What are the steps in the retrovirus phage infection
- the reverse transcriptase carried by the virion reverse the transcription of + ssRNA into DNA
- DNA travels to the nucleus and is incorporated into the host genome
- the provirus in the host DNA is used ot make mRNA to make new virions
What are the four different mechanisms by which viruses produces tumors
- transduction
- insertion of a strong promoter
- inactivation of a tumor supressor gene
- expression of a viral protein that induces transformation
What are the type of virus that can cause transduction
RNA viruses
What are the type of virus that can cause insertion of a strong promoter
retroviruses (insertion of LTR)
What are the type of virus that can cause inactivation of tumor supressor gene
retroviruses (insertion of LTR)
What are the type of virus that can cause expression of viral protein
DNA viruses
What are the genes of HPV that induces transformation of the cells
E6 and E5 genes
