Viruses Flashcards

Question

Describe the replication strategy of the polio virus?

Answer 1

5 stages... 1- virus binds to cell surface receptor CD155 (immunoglobin like receptor) Schindler initiates the creation of a pore in the host cell membrane through which the +ve RNA enters he host cytoplasm 2- VPg protein is cleaved from the viral RNA. Some RNA is transcribed allowing replication of the genome, whereas some is translated into a single viral protein. Translation is initiated at the Internal Ribosome Entry Site (IRES) which is a different mechanism to the normal cap dependant initiation in the host cell. A protease is also translated from the viral genome which stops the normal cap dependant translation of the hosts genome, therefore stopping host protein production Viral polypeptide is cleaved into three precursors....p1-3 3- the viral genome is replicated to create many copies which become templates for synthesis of -ve RNA which is the template for +ve viral RNA which is delivered back into the cytosol 4- some of this viral RNA is translated into more viral proteins 5- capsid proteins are synthesised and form new vision capsid containing new +ve viral genomes. As the host cell is joe unable to produce its own proteins, the cell dies a matter of hours later and the viral capsids are released to infect other cells

Answer 2

The small pox virus has been eradicated since 1977 It is a large animal virus The most deadly human virus in history

Answer 3

Large virus Non symmetrical Double stranded DNA which is fused at both ends forming a circular DNA strand Replicates in the cytoplasm, unlike other DNA viruses Therefore it carries it's own polymerases and replication enzymes with it in the capsid as the hosts replication machinery is in the nucleus Also carries it's own capping and methylating enzymes Still use the hosts energy supplies etc

Answer 4

Four stages to the replication strategy 1- attaches to the host cell and is endocytosed into the cytoplasm 2- partially uncoats allowing access for its own DNA dependant RNA polymerases to translate around 100 mRNA molecules into the cytoplasm. mRNA is processed by methylating and capping proteins to make it available for translation by the hosts machinery. Early genes encode viral polymerase proteins and structural capsid proteins as well as uncoating enzymes 3- late genes begin to be transcribed while the early genes are no longer translated into a protein product Not hey mainly encoded structural proteins for the capsid 4- visions are assembled, some are provided with a coat by the cells Golgi apparatus allowing it to leave he cell before it does. Most however are released when the cell lyses.

Answer 5

Same family of virus that causes mumps | Bind to host cell surface receptors containing sialic acid (sugar)

Answer 6

Bind to host cell surface receptors containing sialic acid (sugar)

Answer 7

Similar to the structure of the influenza virus and attaches to the same receptors Helical, enveloped capsid Negative strand RNA genome Similar replication strategy to influenza

Answer 8

Similar to influenza 3 stages 1- entry into host and attachment to a host cell Attachment to sialic acids on cell surface. Fuses with cell membrane and releases nucleocapsid into the cytoplasm It carries it's own RNA dependant RNA polymerases to replicate its own genome and transcribes its 6 genes. The genes nearest the 3'end are most important for infection and are transcribed in greater numbers Host cell machinery transcribes the viral proteins The -ve genome is translated into a +ve genome in the form of a replicative intermediate 2- the replicative intermediate is the template for the formation of viral -ve genome compiles which form new virions 3- the nucleocapsid a are formed in the cytoplasm and released from the cell by budding

Answer 9

HBV is the hepatitis B virus | It causes liver disease

Answer 10

Enveloped icosahedral virus Partially double stranded DNA genome Contains its own DNA dependant DNA polymerase which has reverse transcriptase ability

Answer 11

Three stages 1- infects mainly liver cells. Several possible receptors that the virus and bind to by unknown mechanisms The genome is carried to the nucleus of the host cell where the +ve DNA strand is spliced together to form a circular DNA molecule which acts as a template for the synthesis of 4 +ve RNA strands One is used for genome replication, the other three are used for viral protein synthesis. 2- the viral capsid is formed and contains the viral RNA along with a newly synthesised polymerase which translates it into DNA 3- the capsid is surrounded by a membrane and studded with viral proteins before being released from the cell. The cell does not die as a result of the infection . The damage to the liver is thought to be as a result of the hosts immune response as opposed to the virus itself

Answer 12

A virus which kills the host cell after infection

Answer 13

Giant cells which have been formed by virally infected cells fusing together, can form multinucleate cells Occurs in measles and HIV

Answer 14

Granular areas where viral components are being synthesised or assembled. This can be in the cytosol, the nucleus or the organelles. Granular inclusion areas can damage the cells structure

Answer 15

Inhibit the synthesis of the hosts DNA The rate of viral protein synthesis may outcompete the hosts protein synthesis Compromise the integrity of the plasma membrane Also the integrity of the inner membranes therefore increasing pH and the dissipation of ion gradients Viral proteins can be inserted into the membrane which cause the immune system to attack it Host cells can also be transformed because of the insertion of the viral genome into its own genome, this can lead to cancerous cells

Answer 16

The time between infection and the onset of symptoms

Answer 17

HIV is present in bodily fluids Affects helper T cells of the immune system Acute phase 1-12 weeks after infection Symptoms of flu Brief peak of virus in the blood stream called viraemia followed by a brief drop in concentration of t helper cells - also referred to as CD4 cells There is then an asymptomatic period of 5-10 years where there are few symptoms The t helper cells then begin to decline rapidly and the patient becomes very susceptible to opportunistic pathogens and tumours.

Answer 18

Incubation period of 1-3 weeks Can cause paralysis due to destruction of motor neurons Most common route of transmission is faecal-oral Initial infection site is the tonsils and lymphoid tissues Can spread to the CNS causing meningitis Most common in children under 5

Answer 19

Highly contagious Spread by respiratory droplets Particularly common in under 5's 10 day incubation period Causes viraemia Symptoms are cough, runny nose, fever, kopliks spots in the mouth and a pussy rash lasting 5-10 days No specific treatment There can be serious complications such as immunodeficiency and secondary infection In some cases the virus enters the brain and causes inflammation A very rare subsequent infection called subacute sclerosing panencephalitis occurs 6-8 years after a measles infection It is a fatal neurodegenerative disease caused by prion proteins

Answer 20

Causes an inflammation of the liver Routes of transmission are same as HIV, sexual, blood and vertical transmission Six viruses that cause hepatitis, HBV being the most common. Death is as a result of the immune response to the infected hepatocytes as opposed to the effect of the virus itself

Answer 21

Viral haemorrhagic fever Muscle pain, circulatory shock, haemorrhage and death First recorded in 1976 Ebola is a zoonose although the reservoir species has not been identified - likely to be fruit bats

Viruses Flashcards

(45 cards)