Intro To Virology Flashcards
What are the 2 components of a virus
•1) a genome consisting of either ribonucleic acid (RNA) or deoxyribonucleic acid (DNA), but not both,
•2) a protein-containing structure (capsid) designed to protect the genome.
What are some additional structural features some virus carry
-•an envelope composed of a protein-containing lipid bilayer, whose presence or absence further distinguishes one virus group from another.
-• Essential enzymes are carried within some viruses e.g RNA Polymerase
• A complete virus particle combining these structural elements is called what
A Virion
What’s a capsid
The protein coat that surrounds nucleic acid.
What’s a nucleocapsid
The nucleic acid plus the capsid
What’s a capsomere
The structural protein units that made up the capsid.
What are surface proteins
These are glycoproteins found on the lipid envelope of viruses that facilitate attachment and entry of the virion into host cells
Shapes of capsid
Helical
Icosahedral
(Prolate, spherical)*
Characteristics of Virus (8)
•Viruses are smaller than bacteria, they range in size between 20-300 nanometers ( nm ).
•Viruses contain only one type of nucleic acid, either DNA or RNA, but never both.
•Viruses consist of nucleic acid surrounded by a protein coat. Some viruses have an additional lipoprotein envelope.
•Viruses lack cellular organelles, such as mitochondria and ribosomes.
•Viruses are obligate cellular parasites. They replicate only inside living cells.
•Viruses replicate through replication of their nucleic acid and synthesis of the viral protein.
•Viruses do not multiply in chemically defined media.
•Viruses do not undergo binary fission
How do viruses replicate
Viruses replicate through replication of their nucleic acid and synthesis of the viral protein.
Classification of virus are based on what
•type and structure of the viral nucleic acid (Genome)
•type of symmetry of the virus capsid (Capsid Symmetry)
•presence or absence of a lipid envelope. (Envelope)
What’s the classification of virus based on genome
•DNA virus or RNA virus
•Linear or circular
•Single or double stranded
(Some viruses are also recognized as segmented)
What are the classifications of DNA genome viruses
•Single-stranded (linear) DNA :(parvoviruses)
•Double-stranded DNA
-Linear genome: adenoviruses, herpesviruses, and poxviruses
-Circular genome: polyomaviruses and hepadnaviruses
What happens to (+) RNA genome in retroviruses
They are not translated into protein but are converted into DNA, which then acts as a template for the production of mRNA
What’s the classification of RNA genome viruses
•Positive-sense (+) RNA
-Same sequence as messenger RNA (mRNA)
-Directly translated into protein
{Exception is the retroviruses in which the (+) RNA genome is not translated but is converted into DNA, which then acts as a template for production of mRNA.}
•Negative-sense (-) RNA
-Sequence complementary to mRNA
-Must be copied into (+) strand to generate mRNAs for protein synthesis
•Double-stranded (+/–) RNA: copying of (-) strand generates mRNA for protein synthesis
3 characteristics of segmented genomes
• Found in the reoviruses, a dsRNA genome, and in three families of (-) ssRNA viruses❗️( orthomyxoviruses, arenaviruses, and bunyaviruses ) ❗️
• Consists of several pieces, or segments, each of which encodes at least one polypeptide
• May undergo reassortment among genomic segments
What 3 (-) ssRNA have segmented genome
Othomyxoviruses
Arenaviruses
Bunyaviruses
What are the classification of viruses based on their capsid symmetry
•Cubic
-The virus particle is icosahedral in shape (almost spherical particle ) and the nucleic acid contained inside the capsid.
•Helical
-The virus particle is elongated or pleomorphic (not spherical), and the nucleic acid is spiral
•Complex
-The virus particle does not confirm either cubic or helical symmetry.
What’s the classification of viruses based on their envelope
•Naked
•Enveloped
Difference between naked and enveloped viruses (7)
Component
Naked: Protein
Enveloped: Protein, Phospholipid, Glycoproteins
Sensitivity to heat, detergent, acid
Naked: Not sensitive (stable)
Enveloped: Sensitive (Labile)
Effect of drying
Naked: Retain infectivity
Enveloped: Loses infectivity
Transmission or mode of spread
Naked: Feacal oral, formite, dust
Enveloped: large droplets, secretion, organ or blood transplants
Host immune response
Naked: Antibody defense
Enveloped: Antibody defense and cell mediated response
Survival in GIT
Naked : yes
Enveloped: no
Release from host cells
Naked: by lysis (death of cell)
Enveloped: by budding (survival of cell) or lysis
Which enveloped virus scan survive in the GIT
Corona and Hepadna virus
Break down the DNA Viruses
DNA viruses
Double stranded. Single stranded
Env. Unenv. Unenv.
Enveloped ddDNA
Hepadna virus (c)
Herpes virus (L)
Pox virus (L)
Unenveloped ddDNA
Adeno virus (L)
Papilloma virus (c)
Polyoma virus (c)
Unenveloped ssDNA
Parvo virus (L)
Which virus replicates outside of the nucleus
Pox virus
What’s the larges DNA virus
Pox virus
