Viral Replication and Genetics

DNA polymerase

Important for DNA replication

Egress

Budding refers ti the ___ part of viral life cycle

DNA dependent DNA polymerase

reads and produces DNA

DNA dependent RNA polymerase

reads DNA and produces RNA

ribosomes

read messenger RNA nucleotide sequence from 5 to 3

mRNA

ready to read by ribosome - positive sense

make mRNA that can be read by the host ribosomes

viral genomes must do what?

Group I/Class I

Use host DNA-dependent RNA polymerase and ribosomes

dividing cells

what does group I/Class I require?

a replicative state (except Parvo)

within group I/Class I DNA viruses can push cell into what?

Group/Class II

Single-stranded DNA is first converted to double-stranded DNA by DNA polymerase

rolling circle replication (RCR)

Most ssDNA viruses contain circular genomes that are replicated via

Group/Class VII

Viruses that have a double-stranded DNA genomes which are segmented (gap in one strand)

gap

what is repaired to create a complete dsDNA genome prior to transcription in Group/Class VII?

reverse transcription

what does Group/Class VII involve?

hepatitis

what is an example of type 7

the cytoplasm (some exceptions)

where do RNA viruses replicate in?

herpes and pox

what are some examples of type 1

parvovirus

what is an example of type 2

nucleus

Retroviridae, Orthomyxoviridae, and some Bunyaviridae which replicate in

Group/Class III

double stranded RNA virus - carry RNA dependent RNA polymerase

Group/Class IV

positive sense signal stranded RNA viruses - genome functions as mRNA - produces neg sense as intermediate

does not require transcription

what is the most important thing about type 4

rotavirus

what is an exampleof type 3

polio snd coronavirus

what are some examples of class 4

Group/Class V

negative sense single-stranded RNA virus - carry RNA dependent RNA polymerase - ambisense TNA genomes

Group/Class VI

single stranded RNA viruses with a DNA intermediate

Group/Class VI

Reverse transcriptase (RT) enzyme synthesizes a DNA strand from the ssRNA strand

influenza and rabies

what is an example of type 5

HIV

what is an example of type 6

nucleus

if the virus has DNA, where does it often enter

cytoplasm

if the virus has RNA, replication and transcription can occur where

RNA-dependent RNA polymerase

what converts - ssRNA to +ssRNA

retroviruses

what carries their own reverse transcriptase

complementation

helper virus

transcapsidation

phenotype mixing

mutation

change in DNA or RNA (nucleotide addition, deletion, rearrangement)

produce antiviral drug resistant or alter antigenicity or pathogenicity

mutations in virus may do what?

error prone

viral polymerase are:

genetic error-checking mechanism

what do RNA viruses lack

Antigenic drift

slow change in viral protein

accumulation of point mutations in nucleic acid

antigenic drift is due to:

influenza HA, HIV gp120

Escape from neutralizing antibodies

influenza

what is an example of a virus that uses antigenic drift

recombination

Exchange of NA (DNA or RNA) between similar viruses

reassortment

viruses with segmented genome - Mixed infection and packaging incorporates different genomic segments in capsids

mixing

reassortment is:

antigenic shift

reassortment can cause

complementation

defective virus, unable to replicate - essential gene deleted or non functional

mixed infection with a wild type virus

complementation:

superinfection

>1 type of virus in a cell

transcaptidation

defective genome replicated - defective genome is packaged in a functional capsid

capsid protein or VAP

transcaptidation may need what:

encoded in the genome of the virus

Processes not provided by the cell must be:

acute infection

rapid and self-limiting

latent infection

dormant, can reactivate

persistent infection

long term, life of host

acute infection

most persistent infections probably begin as what?

when primary infection is not cleared by immune response

when does persistent infection occur?

proteins are not detected

within in a persistent infection, viral genomes may remain after:

persistent infection

When cytopathic effects are absent and host defenses are reduced, what is likely?

eclipse phase/period

uncoating of the genome from the capsid or envelope during the early phase - abolishes its infectivity and identifiable shape

latent phase/period

extracellular virus is not detected

attachment to the surface of the host cell

First step in every viral infection:

collision between the virion and the cell

prerequisite for recognition and attachment

nonmotile

viruses are:

neutralizing antibodies

why is step 1 the most important and essential, intervention

susceptible cells

cell has viral receptors

permissive cells

cell will support viral replication and production of progeny virus

tropism

The predilection of a virus to infect and replicate in aparticular cell or tissue type

attachment

virus penetration is closely linked to

enveloped virus (penetration)

Virus envelope fusing with a host cellular membraneto release nucleocapsid

direct fusion - viropexis

enveloped virus penetration:

endocytosis, viropexis and direct entry

nonenveloped virus penetration

direct fusion

how does virus penetration happen

attachment

which stage of the viral replication cycle is most efficiently blocked by neutralizing antibodies?