III - A. Virology | 1. Classification of viruses. Principles of virus structure. Chemical composition of viruses

Question 1

I. Basics
1. What are viruses?

Answer 1

Question 2

I. Basics
2. Why are viruses Obligate intracellular parasites?

Answer 2

Can only survive within a host cell and depends on it for replication and metabolic processes

Question 3

I. Basics
3. What is the size of viruses?

Answer 3

below the resolution of light microscope
=> Size: 20 nm – 400 nm

Question 4

II. Structure of virus
1. What is virion?

Answer 4

extracellular form of a virus

Question 5

II. Structure of virus
3A. What are the components of viruses?

Answer 5

Question 6

II. Structure of virus
3B. What are the Nucleocapsid Essential components?

Answer 6

• Genome – DNA or RNA
• Capsid: proteins protecting genome

Question 7

II. Structure of virus
3C. What is the genome of virus?

Answer 7

DNA or RNA

Question 8

II. Structure of virus
3D. What is caspid?

Answer 8

proteins protecting genome

Question 9

II. Structure of virus
3E. What is the Envelope of virus?

Answer 9

Envelope: lipid bilayer
- contains proteins eg. spikes
- not all viruses have envelope

Question 10

II. Structure of virus - Genome
4A. How do we classify virus based on genome?

Answer 10

1. DNA viruses
2. RNA viruses (e.g, Retroviruses)

Question 11

II. Structure of virus - Genome
4B. Make a schematic diagram of major viral families based on genome structure and virion morphology.

Answer 11

Question 12

II. Structure of virus - Genome
4C. What are the features of genome of a virus?

Answer 12

• Double stranded (ds) or single stranded (ss)
• Linear or circular
• Segmented NA:
  allows easy recombination – lots of variants

Question 13

II. Structure of virus - Genome
4D. What are the features of retrovirus?

Answer 13

RNA viruses that make a DNA copy of their RNA in the infected cells
=> Reversing the usual direction of NA copy

Question 14

II. Structure of virus
5. How do virus make protein?

Answer 14

• Viruses need mRNA transcribes from their genome to make the cell synthetize virus proteins
• Type of NA in their genome will direct how they get to this point
• RNA viruses need their own RNA polymerase as host cells don’t have such enyzme
• Viruses will use host cell’s machinery for protein sythesis from these

Question 15

II. Structure of virus
6. Make a comparison between DNA and RNA viruses?

Answer 15

Question 16

II. Structure of virus - the caspid
7A. What are the features of caspid?

Answer 16

Question 17

II. Structure of virus - the caspid
7B. How does caspid determine the shape of viruses?

Answer 17

Question 18

II. Structure of virus - the envelope
8A. What are the features of envelope?

Answer 18

Question 19

II. Structure of virus - the envelope
8B. What is the main function of the envelope?

Answer 19

Function: attachement to cell surface

Question 20

II. Structure of virus - the envelope
8C. Give an example of virus with envelope?

Answer 20

Spike proteins

Question 21

II. Structure of virus - the envelope
8D. Make a comparison between enveloped and non-enveloped virus?

Answer 21

Question 22

II. Structure of virus
9. What are the viral proteins?

Answer 22

• capsomeres (clusters of polypeptides)
• enzymes
• matrix proteins
• surface glycoproteins

Question 23

III. Classification of viruses
1. How do we classify virus?

Answer 23

• based on nucleic acid type
• based on host
• based on morphology
• Baltimore-classification

Question 24

III. Classification of viruses
2A. How do we classify virus based on nucleic acid?

Answer 24

1. DNA
2. dsRNA
3. ssRNA
   a. - ssRNA
   b. +ssRNA ( techniqually an mRNA)

Question 25

III. Classification of viruses 2B. Make a schematic diagram for classification of virus based on nucleic acid

Answer 25

Question 26

III. Classification of viruses 3A. What is the basis of Baltimore-classification?

Answer 26

Question 27

III. Classification of viruses 3B. Give the Baltimore-classification

Answer 27

Question 28

III. Classification of viruses 4. Give the classification of viruses based on host

Answer 28

Question 29

III. Classification of viruses 5. Give the classification based on morphology

Answer 29

classification based on capsid shape * helical * cubical (ikkozahedral) * binary * complex