Virus previous exam qs Flashcards
What is virus latency? What is recrudesnce of latent virus? Give example of latent virus
Virus latency is a viruses ability to stay inert in a cell, meaning that once a cell is infected by a virus the virus will always remain dormant in cell.
Recrudescence of latent virus is the reactivation of an latent virus usually due to stress
Herpes
Describe the first 3 stages of virus replication
Adsoprtion - non specific random binding to surface of cell
Attachment - specific binding of ligand of virus to host cell receptor molecule
Penetration - receptor cell endocytosis or nuclear fusion of virus into plasma membrane
Describe the last 4 stages of virus replication
Uncoating - release of nucleic acid from capsid into cell, release of lysogenic enzymes into cytoplasmic vacuoles
Synthesis - synthesis of protein and nucleic acid in cell
Assemble - assembling of virus (self assemble)
Release - budding or cell lysis
Describe Active immunity
Can be natural (over life time) or artificial (vaccines), can be temporal or life long. Allows host immune system to fight foreign cells
Describe passive immunity
Can be natural (placenta) or artifical (anti-serum), can only be temporal (3 weeks). Host immune system cant fight foreign cells
List antiviral drugs which can be used to affect some stages of virus replication
Antibodies can be used to block attachment of HIV
Amanditane can stop uncoating of influenza
Neurominidase inhibitors can stop release of influenza
On what bases are animal viruses classified part 1 (RNA/DNA etc)
RNA/DNA nucleic acid Symmetry non/enveloped \+ or - sense (RNA) non/segmented linear/circular double strand or single strand
On what bases are animal viruses classified part 2 (order etc)
Order Family Sub family species sub species genus strain variant
Describe main characteristics of extracellular phase of virus
Extracellular virus is fragile, the virus can’t live without the host cell and the virus is metabolically inert
Describe the main characteristics of intracellular phase of virus
Intracellular virus thrives, takes over the cells machinery, forces cell to replicate virus and disease may occur
Describe Antigenic drift
Antigenic drift is a point mutation which changes the loop surrounding the receptor molecule of haemagglutinin or in the catalytic site of neurominidase
Describe antigenic shift
Antigenic shift is a change in subtype of haemagglutinin/neurominidase due to a point mutation or genetic reassortment.
Describe the lytic cycle
Lytic cycle is where a phage attaches to a cell, releases nucleic acid into the host cell and takes over the cells machinery, forcing the cell to replicate the virus then makes the cell explode by cell lysis
Describe the lysogenic cycle
Lysogenic cycle is where a phage attaches to a cell, releases its nucleic acid into host bacteria chromosome, allows the cell to replicate so when it replicates the cells contain the viral DNA in host genome
Describe Innate immunity
Innate immunity is immunity you are born with, it is the first and second line of defence of the immune system. It is non-specific and has no memory
Describe adaptive immunity
Adaptive immunity is immunity an organism develops over a life time, it may be acquired naturally or artificially, it is the 3rd line of defence of the immune system and has memory and is specific.
What is a pandemic?
A pandemic is a where a virus/disease affects a country or the world
Describe the 1st line of defence
First line of defence is skin and mucous membranes. Skin protects from outside and can be secreted and mucous traps foreign cells and can force coughing and sneezing, fever also occurs to increase metabolic rate of immune system
Describe 2nd line of defence
2nd line of defence is phagocytes, lymphatic system and inflammation. Phagocytes eat and kill foreign cells and can be neutrophils (first to arrive at scene) and macrophages (bigger later on). Inflammation can destroy/confide infectious agents and the lymphatic system takes fluid from inflammation and puts it back into blood
Describe the 3rd line of defence
3rd line of defence has two arms. T arm provides immunity inside host cell, t cells recognise foreign cells and recruit other cells (phagocytes) to kill.
B arm uses antibodies to kill antigens in extracellular fluid, B cells (plasma) interact with pathogen and check with T(h) cells to make sure pathogen is bad and then makes antibodies to kill.
