Lecture 9: Viruses: Structure, classification and role.

Question 1

What are viruses?

Answer 1

Subcellular genetic elements and obligate parasites. They do NOT have an energy supply and are NOT motile.

Question 2

What are virions?

Answer 2

Virus particles that have genome of EITHER DNA or RNA, and a protective protein shell known as a capsid which surrounds the genome. Clusters of these capsids are known as capsomers.

Question 3

What features are there in virions?

Answer 3

Nucleocapsids: Capsid associated with viral nucleic acid.

Envelope: Lipid membrane that surround the nucleocapsid. (Naked viruses lack this).

Matrix: Describes protein layer that connects capsids and envelope glycoproteins.

Question 4

What shapes of capsids are there?

Answer 4

Icosahedral symmetrical capsids, helical capsids.

Question 5

True or false? Genomes of viral nucleic acid can either be single or double stranded DNA or RNA.

Answer 5

True. In fact, their single stranded RNA (ssRNA) can also be -ve or +ve sense. +ve means same as mRNA, allowing ribosomes to read it directly and replicate.

-ve means complementary to mRNA. They can also be linear, circular or segmental.

Question 6

What 3 classifications of viruses are there?

Answer 6

Kind of nucleic acid. Strategy of replication. Morphology of virion.

Question 7

Arboviruses infect what?

Answer 7

Insects.

Question 8

True or false? Detecting a virus in a pathology test implies causality.

Answer 8

False.

Question 9

What are the steps involved in detecting a virus?

Answer 9

Use an electron microscope, cultivate virus (sometimes cannot as not all viruses have a culture system), detect protein, see the serological response of host, and detect gene via PCR.

Question 10

What is SARS?

Answer 10

Atypical pneumonia, transmitted by airborne droplets, a corona virus.