True/False: Viruses cannot infect all forms of life.
False, all life-forms can be infected by viruses.
Define a virus.
Noncellular particle that must infect a host cell, where it reproduces.
The virus particle, or _____, consists of nuclei acid (DNA or RNA) contained within a protective protein ______.
virion, capsid
Name the famous person: developed the first polio vaccine in 1952.
Josan Salk
Each species of virus infects a particular group of host species, or ____ _____.
host range
Small viruses commonly have a small genome, encoding under ____ genes.
ten, the genes may overlap in sequence.
Large viruses may have more than ____ genes.
100, indeed, mimivirus encodes over 1,000 genes
_____ are RNA molecules that infect plants.
Viroids
Viroids have no _____ _____.
- Are replicated by _____ RNA polymerase.
- Some have ______ ability.
- protein capsid
- host
- catalitic
_____ are proteins that infect animals.
Prions
True/False: Prions have nucleic acid components.
False, they have none.
- Have an abnormal structure that alters the conformation of other normal proteins
The viral ____ is composed of repeated subunits, which maximizes the capacity while minimizing the required number of genes.
capsid
The viral ____ packages the viral genome and elivers it into the host cell.
capsid
Icosahedral viruses are _____ and have 20 _____ triangular faces, exhibiting _____ symmetry.
- symmetrical
- identical
- rotational
In some icosahedral viruses, the capsid is enclosed in an _______, formed from the cell membrane, which comes from the _____ cell.
envelope, host
The icosahedral viruses' envelope contains glycoprotein _____, which are encoded by the virus.
spikes
Between the envelope and capsid of icosahedral viruses, ______ proteins may be found, which come from either the host or virus.
tegument
Name the virus type:
- the capsid consists of a long tube of protein, with the genome coiled inside
- vary in length, depending on genome size
- include bacteriophages as well as animal viruses
Filamentous viruses
Filamental viruses show ______ symmetry.
helical
The pattern of capsid monomers forms a helical tube around the genome, which usually winds helically within the tube.
Pox viruses:
- their genome is surrounded by _____ layers
- A core envelope studded with ____ proteins
- An _____ membrane
- Also contain a large number of ______ proteins.
- spike
- outer
- accessory
Viral genomes can be:
- ____ or ____
- ____ or ______
- _____ or _____
- DNA, RNA
- Single-, double-stranded (ss or ds)
- Linear, circular (linear is more common)
Name 3 things that the viral genome may code for:
1. Capsid
2. Envelope proteins
3. Any polymerase not found in the host cell
A classification system for viruses created by the ICTV is based on several criteria:
- _____ composition
- Capsid _______
- _____
- _____ of the virion
- ______ range
- genome
- symmetry
- envelope
- size
- host
Name the famous person:
- In 1971, proposed the primary distinctions among classes of viruses be:
- genome composition (RNA or DNA)
- route used to express mRNA
- shared 1975 Nobel Prize for work in retroviruses
David Baltimore
Which of the 7 fundamental groups of viral species is this: double-stranded DNA
- uses its own or host DNA polymerases for replication
Group I
Which of the 7 fundamental groups of viral species is this: single-stranded DNA
- Required DNA polymerase to generate a complementary strand
Group II
Which of the 7 fundamental groups of viral species is this: double-stranded RNA
- Requires RNA-dpeendent RNA polymerase to make mRNA and genomic RNA
Group III
Which of the 7 fundamental groups of viral species is this: (+) single-stranded RNA
- Requires RNA-dependent RNA polymerase to make a template for mRNA and genome replication
Group IV
Which of the 7 fundamental groups of viral species is this: (-) single-stranded RNA
- Requires RNA-dependent RNA polymerase to make mRNA and replicate its genome
Group V
Which of the 7 fundamental groups of viral species is this: RNA retroviruses
- packages its own reverse transcriptase to make dsDNA
Group VI
Which of the 7 fundamental groups of viral species is this: DNA pararetroviruses
Group VII
Definition: Genes of common ancestry in two genomes that share the same function.
orthologs
A ____ ____ ____ is a DNA sequence that can express a recombinant gene in an animal or plant cell.
gene transfer vector
The viruses used as gene transfer vectors are those whose replicative cycles establish a viral genome within the _____ _____.
host nucleus
Some of the first viral vectors were made from double-stranded DNA viruses such as _______.
adenoviruses
An exciting class of gene transfer vectors are derived from _____, such as the lentivirus HIV
- Lentiviral vectors or tentivectors
retroviruses
In general, gene therapy is approved only for conditions that are ___-_____ and for which alternative therapies are ______.
life-threatening, inadequate
Safety features of viral vectors include:
- _______ virulence genes
- avoiding genome ______ next to oncogene
- altering tissue _____
- _____ germ-line infection
- deleting
- insertion
- specificity
- avoiding
A virus is a noncellular particle that can reproduce only within a ______ ____.
living cell
A complete viral particle is called a _____, and is composed of a nucleic acid genome, surrounded by a protein _____.
virion, capsid
Viruses can be divided into two main types:
symmetrical and asymmetrical
The Baltimore system classifies viruses mainly on their means of:
mRNA synthesis
Viruses have been used for ___ ____.
Examples: Lentiviruses and adenoviruses
