Basic Virology Flashcards
What 2 bacteria require living cells to survive?
Chlamydia and Rickesttsiae
Do viruses need living cells to survive?
Yes, they are obligate intracellular parasites
Viruses consists of
NA (DNA or RNA, not both) and proteins, some possess an envelope
Viruses are simple replicons, yet
they can take over the host cells machinery and use hots enzymes for replication
Size of viruses
15-300nm, must use ELECTRON microscopy
Virion
complete viral particle, able to infect host and replicate
Genetic material
dsDNA, ssDNA, (+)ssRNA, (-)ssRNA, dsRNA with identical or complementary strands, linear or circular, usually condensed with histones
Each infectious virion possess the same
NA
Protomer
protein subunit of the capsid (viral protein envelope)
Protomers can be arranged 2 ways:
icosahedral or helical
Capsomers
arrangement of protomers that form a capsid with icosahedral symmetry
capsid
protein shell that self-assembles from protomers and encloses a core of NA
There are 3 architectural structures of a capsid
complex symmetry, cubic/icosahedral symmetry, helical symmetry
Complex symmetry
viruses with unresolved arrangements (not solved yet)
cubic/icosahedral symmetry
20 faces, each is an equilateral triangle, protomers arranged into capsomers
helical symmetry
enveloped or non-enveloped nucleocapsid formed by a single repeating protomer and ssRNA
nucleocapsid:
protomers assembled in a helical structure around the nucleic acid genome of the virus (capsid + NA + associated proteins)
Nucleocapsids can be enveloped or not, non-enveloped nucleocapsids are
stable, resistant to desiccation, acids, and detergents
Nucleocapsids may have an envelope that is derived from
host NM, CM, or organelle membrane
Peplomer
protein on surface of enveloped nucleocapsids (spikes) that play a role in attachment to cell receptor
Tegument and Matrix protein
layer between envelope and nucleocapsid that has complex function and maintains shape
Nucleocapsids can be enveloped or not, enveloped nucleocapsids are
fragile, easily disrupted/denatured, sensitive to desiccation and detergents
If an enveloped virus is disrupted
the virus becomes inactive
Nearly ALL enveloped viruses are transmitted via
arthropods in respiratory droplets or bodily fluids
Viruses are classified by 4 categories:
type and polarity of NA, type of capsid symmetry, presence of envelope, quantitative measure of capsid architecture
5 Orders of Viruses
Caudovirales, herpesvirales, mononegavirales, nidovirales, picornavirales
Viral clade
all descendants from a common ancestor as determined by sequence similarity w/in clade and sequence variation among population
Virus serotypes
based on antigenic diversity
Examples of clades (Hepatitis C)
6 major clades with genotypes differing by 30-50%
Quasisepsis
chronic viral infection that spontaneously generates a population of virions with significant diverse genomics
Medical significance of clades:
immune evasion
