ddt 17 Flashcards
— is a tiny infectious particle consist of a nucleic core surrounded by protein coat called —
- virus
- capsid
viruses require —- to reproduce ( as: chick embryos in labs )
living organism/ host
the properties of virus
- not cellular
-dont respire - no metabolism of their own
- don’t break down carbon compounds
- don’t die
the three morphological classification
1- helical ( as tobacco mosaic virus )
2- icosahedral: geometric icosahedron of 20 equilateral triangular faces( as adenovirus )
3- combined or complex structures ( as bacteriophage )
the core consist of — surrounded by protein — of varying —-
- rna or dna
- capsid
- geometric configuration
some viruses have —- envelop which in addition derived from the —-
- lipoprotein
- membrane of the hosts cell
propagation: life cycle
1- the virus gains entry by — and is carried to the cytoplasm in a — via the cell membrane
2- leaving its protein capsule — on the cells surface
3- viral — will be released over the genetic machinery of the host cell
4- viral – becomes incorporated into the dna of the host and assuming command of —
5- the host sytheise the —- rather than its own so new viruses will be —- and — completing the life cycle
-endocytosis, vacuole
- redundant
- nucleic acid
- dna, genetic control
- viral proteins, generated and released
virus is dependent on — to propagate
living cells
they enter the —- and redirect the cells —-
host , metabolism
they substitute the cells dna with
their own and produce more viruses internally
the viral propagation stages:
1- attachment: involves the interaction of the viron w/ specific receptor sites in the surface of the hosts cell
2- penetration: viral particles is taken into the cell and sometimes it involves endocytosis
3- uncoating: separation of the viral nucleic acid from the capsid and now the virus is non-effective
4- eclips/replication: viral particles present as small non infective subunit within the host cell and virus is not visible
5- assembly; newly synthesised viral genomes and capsid proteins come together to form new
6- release:
-non-envelope viruses generally lyse or burst the cell
- envelope viruses leave the host by budding process resembling exocytosis
the synthetic and replicative phase of the virus is highly – and extremely — at a — level
- regulated
- complex
- molecular
— control over the hosts sythetic and metabolic machinery depending on —-
- free viral nucleic acid
- virus genome dna/rna
enters the hosts cells nucleas and replication the nuclease and transpiration in the nuclease
dna viruses except poxvirus
is replicated in the cytoplasm and transprption in the cytoplasm
rna viruses except retrovirus
the viral nucleic acid alters the — of the host cells and trusts to synthesise the building block for new viruses
genetic expression
the — becomes a message for sythesizing the viral protein for translation
rna
viruses w — sense rna molicles contain the correct message for traslation into proteins but —- need to be converted into —
- +ve
- -ve convert into +ve
in the next phase the new rna is synthesised by using
host nucleotide, proteins for the capsid, spikes, viral enzymes are syethised on the hosts ribosomes using its amino acids
rna viruses replication takes place in the — and are placed into — depending on the —
cytoplasm and are placed into 4 groups depending on their mode of replication
the —- ( aka whether or not it can be used directly by ribosomes to make proteins) of single strand rna largely determines the replicative mechanism and —
polarity and the genetic material aka whether its single or double stranded
rna virus uses the town — enzymes to create copies of themselves
rna replicase
rubella virus uses
rna polymerase and is membrane fusion
the shape of the rubella virus — and it causes —- but —- is possible
- icosahedral single strand of rna
- red rash and fever rubella, German measles and heart failure in infected infant
- vaccination
Viruses by their nature interrupt — and may cause — or —-
- normal cell cycle
- asymptomatic
- malignt or benign growth
viral virulence can infect one species like — or different species of mammals w broad ranges
- small box
- rabies virus
enzymes produced which erode the cell wall (bacteria)/ cell membrane and cause the cell to rupture;
these are terme
lytic or virulent viruses
here viral DNA/RNA becomes incorporated into the genome of the cell and coexists with the cell;
temperate or lysogenic
viruses may have both —- and — and eventually — becomes activated into — phase
- lytic and lysogenic
- lysogenic to lytic phase
Viral DNA incorporated into bacterial DNA is called a
prophage
lysogenic infection steps:
- phages can be spread to infect bacteria
- viral dna is incortated into bacterias dna called prophage
- bacteria can divide by fission copying the provirus
- when its activated it can replicate new viral particles to make more phages and enter lytic stage
treatment of viruses is — because they use ——
difficult, they use the hosts own processes for propagation
viral chemotherapy: New therapies involve compounds such as
a) Acyclovir, in cold sore creams on Herpes virus ( it won’t cure it but cam lessen the outbreaks)
b) Interferon, used in treatment of AIDS
Early detection and prevention are the current approaches to treatment of viral diseases
true or false: viruses can be responsible for human cancer
true
Human Papillomavirus are
- dna virus
- warts ( trees like warts can develop an infection and weakened the immune system )
-non malignant tumor
sub viral particles:
infectious agents smaller by an order of magnitude than viruses have been identified in recent years:
- viroids
- prions
Short single strands of RNA;
Circular structures of 250-400 nucleotides
Don’t code for any proteins;
No protective coat (unlike viruses)
Copied by the host RNA polymerase;
Infect plant cells.
viroids
prions
**
Prion means - ‘Proteinaceous infectious particle’;
Even smaller than a viroid and consisting of just a protein of 208 Amino Acids;
Only infectious agent without nucleic acid;
Induces normal PrP proteins to misfold thus forming another prion
— induce formation of an — fold ie. the protein polymerises into an aggregate consisting of tightly packed beta sheets
- prions
- an amyloid
prions are involved in:
-‘Spongioform Encephalopathies’ with
long incubation periods (Previously known as ‘Slow virus’ )
- infects animals like:
- scrapie in sheep
- BSE : bovine sponigferom encephalopathy in cattle aka mad cow disease
- prions in humans:
- kuru : a spongiofrom encephalophy caused by the consumption of infected human brain tissue which affects the brain and nerves
- CJD: Creutzfeldt-Jacob Disease)
New variant CJD [vCJD] in Britain appears to have crossed the species barrier from cattle.
