Viruses

Question 1

Basic virology

Answer 1

• have DNA or RNA NOT BOTH
• have no small ions or polysaccharides (they glycosylate proteins by using host enzymes
• either enveloped or naked (more difficult to destroy)

Question 2

Viral shape 
(recognition of shape allows drugs to be designed to target them)

Answer 2

Filovirus - e.g. Ebola

Question 3

Obligate intracellular parasites

Answer 3

• have no genes that encode for means of energy generation of protein synthesis
• hijack host organisms in order to support their own replication

Question 4

Virus growth

Answer 4

Increase is sudden

- cell bursts releasing a huge number of viruses all at once

Question 5

RNA or DNA

Answer 5

• single stranded SS or double stranded DS
• SS may be:
  (+) can serve as mRNA and be directly translated into a protein
• linear, circular or nicked
  (-) cannot serve as mRNA so cannot be directly translated into a protein e.g. Ebola or HIV
• unsegmented or segmented (allows reassortment of DNA - explains the adaptability of the flu virus)

Question 6

Capsid

protein outer coat

Answer 6

• individual subunits are called capsomers
• protects the inner Nucleic acid from harsh environmental conditions
• may be involved in the attachment to host cells
  Either ICOSAHEDRAL OR HELICAL

Question 7

Bacteriophage

Answer 7

Viruses that infect bacteria

• involved in the transfer of antibiotic resistance
• assist in the ability of the bacteria to infect cells

Question 8

Successful infection and replication

host cell must have the cellular machinery the virus needs for replication

Answer 8

• the cell must contain a receptor for the virus to bind to via a ligand in order to initiate an infection
• the ligand is on the capsid of naked viruses and on the envelope of the enveloped viruses
  There can be many different receptor involved in the infection process - some viruses can’t affect humans as our cells don’t have the correct receptors

Question 9

Successful Replication

Answer 9

• infection is productive

- host cell is permissive for the virus

Question 10

Baltimore Scheme

Answer 10

based on the relationship between the viral genome. And the mRNA used for translation during the expression of the viral genome

Question 11

Medical Virology

Answer 11

• use the Nucleic acid type and envelope as the main classification
• representative of how easily the virus is destroyed by disinfectants
  ENVELOPED viruses are generally more susceptible to disinfectants than non-enveloped

Question 12

DNA viruses

Answer 12

ENVELOPED 
- Hepatitis B
- Herpesvirus 
NON-ENVELOPED 
- papillomavirus (warts and cervical cancer)

Question 13

RNA viruses

Answer 13

ENVELOPED 
- rubella 
- HIV (AIDS) 
NON-ENVELOPED 
- picornavirus (polio, hepatitis A, colds)

Question 14

Effects of virus on host cell

drugs that suppress viral replication have no effect on integrated DNA

Answer 14

Death of cell - often during release of virus
Cytopathic effects - caused by viral replication
- inclusion bodies (site of active virus synthesis) e.g. Negri bodies of rabies virus
- syncytia formation (giant, multinucleated cells formed by the fusion of plasma membranes)
- chromosomal damage
- inhibitor of host cell protein, RNA or DNA synthesis
Cancer
- retroviruses - turn on cellular oncogenes that cause cells to proliferate uncontrollably
- inactivate tumour-suppressor proteins that normal act to keep the cell from going through the cell cycle uncontrollably

Question 15

Ebola

Answer 15

RNA SS (-) 
Haemorratic - disorders blood clotting and integrity of blood vessels

Question 16

Compromised immune systems

Answer 16

• show different systems to that shown in a healthy individual
• die quicker as the pathogen is not being opposed by the immune system

Question 17

Incubation period

Answer 17

Time for damage to be sufficient for symptoms to show

Question 18

Asymptomatic infection

Answer 18

• virus is replicated and can be transmitted without causing any visible symptoms in the host

Question 19

Latent infection

Answer 19

the presence of the organism without any symptoms associated
- can lead to the reactivation of the organism