EXAMENVRAGEN EERSTE ZIT 2023-2024
Q1: Baltimore classification: principle, classes (+ example) + rules/definitions
By just knowing the genome structure, the Baltimore classification system enables to deduce how mRNA is
made from the viral genome and how the genome is copied to make more genomes (they first have to make
their genome dsDNA)
Definitions/rules:
1. mRNA (‘ribosome ready’) is always the plus (+) strand
2. DNA of equivalent polarity is also the (+) strand
3. RNA and DNA complements of (+) strands are negative (-) strands
4. Not all (+) RNA is mRNA
MCQ: what is not always encoded by genomes of eukaryotic viruses
- protein synthesis machinery
- membrane biosynthesis
- centromeres or telomeres found in standard host chromosomes
Q2: Schematic overview of viral replication cycle (drawing) + explain each step
, Q3: Viral mRNA 5’ capping: why? Where does it occur
Viral mRNA capped at 5’ end
specific 7’ methyl guanosine triphosphate caps
reasons:
transport mRNA from nucleus to cytoplasm
protection of mRNA degradation by exonucleases
initiation of translation: binding site of initiation factors
most viruses that transcribe in nucleus use cellular capping enzymes (ex. influenza virus snatches caps
from cell mRNAs)
viruses that transcribe in cytoplasm:
often encode own capping enzymes (poxviruses, coronaviruses, reoviruses)
snatch caps from cellular mRNA’s (bunyaviruses)
produce uncapped transcripts (picornaviruses)
cap snatching influenza virus
Endonuclease activity in viral RdRp cleaves nucleotide sequence (10-20nt) from the 5’ end of
host mRNAs
happens in nucleus in (Influenza virus) or in cytoplasm (other segmented ss(-)RNA viruses)
‘snatched’ cap used to prime transcription on the viral genome
MCQ: which virus that enters via the respiratory tract causes generalized disease
- Herpesviridae, Paramyxoviridae, Matonaviridae (Rubellavirus), Picornaviridae, Bunyaviridae,
Arenaviridae (Lassafever virus)
- Non rhino
Q4: HHV5: other name, what type of disease does it cause in different types of patients & what arm of the
immune system can keep the virus latent
= cytomegalovirus:
First isolated in 1956 as ‘salivary gland virus’
Owl’s eye inclusions
1960: cytomegalovirus
Incubation period: 1 month
Immunocompetent persons:
Foetus:
Vertically transmitted
Congenitalbrainabnormalities
0,2-2%ofallnew-borns
Immunocompromised patients: V-5 or CMV
5.1 Disease
HIV+: CD4-count<50cells/ml CMV retinitis loss of vision
Q1: Baltimore classification: principle, classes (+ example) + rules/definitions
By just knowing the genome structure, the Baltimore classification system enables to deduce how mRNA is
made from the viral genome and how the genome is copied to make more genomes (they first have to make
their genome dsDNA)
Definitions/rules:
1. mRNA (‘ribosome ready’) is always the plus (+) strand
2. DNA of equivalent polarity is also the (+) strand
3. RNA and DNA complements of (+) strands are negative (-) strands
4. Not all (+) RNA is mRNA
MCQ: what is not always encoded by genomes of eukaryotic viruses
- protein synthesis machinery
- membrane biosynthesis
- centromeres or telomeres found in standard host chromosomes
Q2: Schematic overview of viral replication cycle (drawing) + explain each step
, Q3: Viral mRNA 5’ capping: why? Where does it occur
Viral mRNA capped at 5’ end
specific 7’ methyl guanosine triphosphate caps
reasons:
transport mRNA from nucleus to cytoplasm
protection of mRNA degradation by exonucleases
initiation of translation: binding site of initiation factors
most viruses that transcribe in nucleus use cellular capping enzymes (ex. influenza virus snatches caps
from cell mRNAs)
viruses that transcribe in cytoplasm:
often encode own capping enzymes (poxviruses, coronaviruses, reoviruses)
snatch caps from cellular mRNA’s (bunyaviruses)
produce uncapped transcripts (picornaviruses)
cap snatching influenza virus
Endonuclease activity in viral RdRp cleaves nucleotide sequence (10-20nt) from the 5’ end of
host mRNAs
happens in nucleus in (Influenza virus) or in cytoplasm (other segmented ss(-)RNA viruses)
‘snatched’ cap used to prime transcription on the viral genome
MCQ: which virus that enters via the respiratory tract causes generalized disease
- Herpesviridae, Paramyxoviridae, Matonaviridae (Rubellavirus), Picornaviridae, Bunyaviridae,
Arenaviridae (Lassafever virus)
- Non rhino
Q4: HHV5: other name, what type of disease does it cause in different types of patients & what arm of the
immune system can keep the virus latent
= cytomegalovirus:
First isolated in 1956 as ‘salivary gland virus’
Owl’s eye inclusions
1960: cytomegalovirus
Incubation period: 1 month
Immunocompetent persons:
Foetus:
Vertically transmitted
Congenitalbrainabnormalities
0,2-2%ofallnew-borns
Immunocompromised patients: V-5 or CMV
5.1 Disease
HIV+: CD4-count<50cells/ml CMV retinitis loss of vision
