Lecture 5 (Viruses)

Question 1

What are viruses?

Answer 1

Acellular organisms that cannot survive without a host

Question 2

What is the viruses’ composition?

Answer 2

1. Genetic Material (DNA & RNA)

2. A protein coat surrounding the genetic material.

Question 3

How big are the viruses?

Answer 3

Vary between 10-400 nm.

Question 4

Which organisms do they infect?

Answer 4

The infect all types of organisms

Question 5

What is capsid?

Answer 5

A protein coat that surrounds and protects the genetic material of the virus.

Question 6

What is the difference between a Naked and Enveloped virus?

Answer 6

Whether a cell has a envelope of lipids that surrounds the capsid.

Question 7

What is the term used to describe caspid+dna?

Answer 7

Nucelocapsid

Question 8

What do capsids compose of?

Answer 8

Multiple units of capsomers which contain protomers.

Question 9

What are the different types of symmetry that the capsomers can be arranged?

Answer 9

Helical
Icosahedral
Complex

Question 10

What possible forms of DNA can be found in the virus genome?

Answer 10

Single/Double stranded DNA/RNA.

Question 11

What possible arrangements can the DNA/RNA be in viruses?

Answer 11

Linear
Circular
Segemented

Question 12

What are the 5 main steps of a virus life cycle?

Answer 12

Attachement
Entry
Synthesis
Assembly
Release

Question 13

What are the 2 types of Viral Infections? (In prokaryotic cells)

Answer 13

Lytic and Lysogenic

Question 14

What do Lytic infections cause in cells?

Answer 14

They cause the killing of the host cell

Question 15

What are Lysogenic infections capable of?

Answer 15

They are able to produce a lytic phage or be integrated into the Lysogen’s genome.

Question 16

How can a lysogenic phage become a virulent phage?

Answer 16

Upon induction (changes in growth conditions, UV radiation)

Question 17

What is the definition of Lysogeny?

Answer 17

The relationship between the temperate phage and host bacterium.

Question 18

What is a temperate phage?

Answer 18

The phage is able to become lytic or lysogenic

Question 19

What are the steps to the replication of a RNA Enveloped Virus (HIV) (Retrovirus)?

Answer 19

1. HIV virus fuses with the host cell membrane
2. Capsid is broken down to reveal RNA genome and Reverse Transcriptase
3. Enzyme is able to form a copy of the DNA that then is incorporated into the host genome.
4. This mRNA can go two ways : become the RNA for next generation or form the viral proteins and envelope glycoproteins.
5. Budding from cell + RNA genome crease the new virus.