Viruses

Question 1

What are viruses?

Answer 1

Tiny, infectious particles called OIPs (Obligate Intracellular Parasites).

Question 2

Viruses discovered?

Answer 2

TMV (Tobacco Mosaic Virus), 1930’s, filtered out from plant.

Question 3

Structure of Viruses

Answer 3

All viruses contain:
1. Nucleic acid genome- can be ss or ds DNA or RNA.
2. Capsid- Protein coat/shell/container for genome.

Not all viruses contain:
1. Envelope- Derived from host plasma membrane + lots of glycoprotein spikes
2. Tail Fibers & Tail sheaths.

Question 4

Shapes of Viruses

Answer 4

a. Spiral
b. Polyhedron
c. Complex - bacteriophages, “lunar lander”

Question 5

Lytic Cycle

Answer 5

1. Attachment - species specific or general
2. Penetration - entry of genome (capsid?) into host cell
3. Biosynthesis - Using host’s cellular machinery to make viral proteins/genomes, viral parts
4. Assembly/Maturation - of new viruses
5. Lysis - release, lysozyme ruptures wall, not envelope virus.

Question 6

Lysogenic Cell cycle

Answer 6

1. Viral DNA inserted into host DNA, becomes a provirus (if in a bacteria, called a prophage).
2. Viral genome then copied & divides w/ host
3. Occasionally, prophage exits bacterial chromosome -> lytic cycle.

Question 7

Bacterial anti-viral Defense

Answer 7

a. Restriction-Modification system
b. CRISPR-Cas system.
(Clustered Regularly Interspaced Short Palindromic Repeats).

Question 8

Animal Viruses

Answer 8

1. Attachment
   1.1 Fusion & endocytosis
   1.2 Uncoating
2. Biosynthesis
3. Assembly & Maturation
4. Release
   4.1 Budding release for enveloped virus
   4.2 Rupture release for naked virus

Question 9

Plant Viruses

Answer 9

Over 2,000 types currently known.
a. Vector = pollinators, humans,
b. Blight, wilt, tumor
c. can spread through plasmodesmata

Question 10

Retroviruses

Answer 10

When virus does reverse transcriptase to get Viral DNA into nucleus (ssRNA -> dsDNA).

Question 11

Classes of Viruses decided by?

Answer 11

Nucleic acid type (DNA, RNA) & the # of strands (ss or ds).

Question 12

Virions

Answer 12

New viruses.

Question 13

Viroids

Answer 13

Infectious RNA - only infects plants

Question 14

Prions

Answer 14

Infectious Proteins - Only infects animals

Question 15

Phages

Answer 15

Bacteriophages. Viruses that solely target and kill bacteria cells.

Question 16

Types of Virus Release from Host cells

Answer 16

Budding: Steal plasma membrane, inside of cell is cooked.
Ruptures: Burst cell open, cell is cooked.

Question 17

Virulent Phage

Answer 17

A phage (bacteriophage) that only replicates via the lytic cycle.

Question 18

Temperate Phage

Answer 18

Phages capable of both lytic and lysogenic cycle.

Question 19

Prophage

Answer 19

A bacteriophage genome that is integrated into the circular bacterial chromosome or exists as an extrachromosomal plasmid within the bacterial cell, viral DNA.

Question 20

Rhinoviral

Answer 20

Common cold, lytic

Question 21

HIV

Answer 21

Lysogenic. Causes immuno deficiency.