intro to virology

Question 1

viruses are:

Answer 1

submicroscopic (obligate intracellular parasite because they don’t have mitochondria) (an energy generating system)

Question 2

viruses are not smaller than:

Answer 2

bacteria

Question 3

the only form of reproduction of viruses is:

Answer 3

using the machinery of the cell that they infect

Question 4

viruses vs other organisms:

Answer 4

viruses = lack genetic information
lack ability to synthesise proteins
new infectious viruses do not grow or undergo division
are produced from the assembly of performed components

Question 5

viruses can possess enzymes ?

Answer 5

yes (eg, RT or RNA dep polymerase), but they can’t do any work without the cell scaffolding or they can possess a nucleic acid but only one of the 2 (DNA or RNA)

Question 6

The structure of viruses

Answer 6

• capsid (protects viral nucleic acid + made up of capsomeres
• envelope with lipids (NB: the outer surface = to recognise + interact w the cell host
• viral genome (RNA/DNA) (they code)

Question 6

how can viruses commandeer cells

Answer 6

use a receptor binding protein

Question 7

what are non-structural proteins?

Answer 7

protein that encoded by a virus is expressed in infected cells, but not incorporated into the virion particle.

Question 8

virion meaning ?

Answer 8

virion, an entire virus particle, consisting of an outer protein shell called a capsid and an inner core of nucleic acid (either ribonucleic or deoxyribonucleic acid—RNA or DNA). The core confers infectivity, and the capsid provides specificity to the virus.

Question 9

enveloped viruses

Answer 9

• DNA viruses: Herpesviruses, Poxviruses, Hepadnaviruses
• RNA viruses: Flavivirus, Toga virus, Coronavirus, Hepatitis D,
  Orthomyxovirus, Paramyxovirus, Rhabdovirus, Bunyavirus,
  Filovirus
• Retroviruses

Question 10

non-enveloped viruses

Answer 10

• DNA viruses- parvovirus, adenovirus and papovavirus.
• RNA viruses- Picornavirus, Hepatitis A virus and Hepatitis E virus.

Question 11

how do we get the diseases caused by viruses ?

Answer 11

• Sensitivity: receptors define tropism (cell, host, species)
• Permissiveness: Cell allows complete replication (presence
  of cellular factors)
• Virulence: viral multiplication
  (sometimes there are lesions without viral multiplication (eg: oncogenic viruses: (viruses that end with V)

Question 12

The 7 stages of a virus within a host cell:

Answer 12

1- attachment
2- entry
3- decapsidation
4- transcription, replication, translation
5- assembly (maturation)
6- budding
7- release

Question 13

satellite viruses:

Answer 13

lack one or more genes so they entirely depend on the assistance of a “helper virus” (coinfection), (ex: HDV + AAV)

Question 14

viroids:

Answer 14

circular ssRNA molecules that only affect plants + responsible for commercially important disease

Question 15

re-emerging viruses:

Answer 15

from animals or new threats from same viruses, is usually a consequence of an alteration of the ecosystem, climate change, human interactions with reservoirs or vectors, or international travel and commerce