Lecture 1

Question 1

What is the ratio between viruses and cellular life?

Answer 1

10:1

Question 2

How much viral DNA is in the human genetic material?

Answer 2

8%

Question 3

How much viral DNA do human have in blood?

Answer 3

70%

Question 4

How many bacteriophage particles in the ocean?

Answer 4

10^31

Question 5

How much does a bacteriophage weigh?

Answer 5

10^-15 grams or 1 femtogram

Question 6

How are viruses beneficial?

Answer 6

Catalyze movement of nutrients from organisms
Kill 20-40% of ocean microbes everyday
Transfer genes between organisms
Prevent and cure diseases

Question 7

How did viruses advance cell biology research?

Answer 7

• Identification of promoters for eukaryotic RNA polymerases
• Cellular DNA replication enzymes
• Reverse transcriptase
• RNA-dependent RNA polymerases
• RNA splicing
• Translation
• Identification of oncogenes

Question 8

What is a virus?

Answer 8

Infectious obligate intracellular parasite

Question 9

What do virus particles contain?

Answer 9

Genetic material (DNA or RNA)
Capsid
Envelope (optional)

Question 10

What are the two phases of a virus?

Answer 10

Inanimate phase (virion)
Multiplying phase

Question 11

True or false: Viruses are passive

Answer 11

True: They are completely at the mercy of their environments. Viruses don’t actually “do” anything to infect

Question 12

How were viruses first visualized?

Answer 12

Electron microscopy (1930s)

Question 13

What are different physical attributes of a virus?

Answer 13

Nature/sequence of nuclei acid virion
Symmetry of capsid
Presence of envelope
Dimensions of virion and capsid

Question 14

What is the envelope of a virus made of?

Answer 14

Lipid membrane

Question 15

Taxonomy of virus?

Answer 15

Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 16

-virales is….

Answer 16

The order of the virus

Question 17

-viridae is….

Answer 17

The family of the virus

Question 18

-virus is …..

Answer 18

The genus of the virus

Question 19

What is the infectious cycle of a virus?

Answer 19

1. Binding to cell receptor
2. Entry and uncoating
3. Early gene expression
4. Replication of viral genome
5. Late gene expression
6. Assembly of virions
7. Exit

Question 20

What determines tropism in viruses?

Answer 20

Cellular receptors are specific for each virus and host species

Question 21

How do bacteriophages inject their genome into the cell?

Answer 21

Bacteriophages have special tails that drill holes and inject their genome into the host cell

Question 22

How do plant viruses enter the cell?

Answer 22

Enter due to damage to the cell wall

Question 23

How do animal viruses enter the cell?

Answer 23

Through membrane fusion or endocytosis

Question 24

What is virus uncoating?

Answer 24

Capsid of virus disintegrates to release genome

Question 25

What does the molecular pathway to early gene expression depend on?

Answer 25

Whether the genome is initially DNA, RNA, ds, ss, etc

Question 26

What is the difference between early and late proteins?

Answer 26

Early: usually directs replication of genome
Late: typically structural proteins used to make viral particles

Question 27

Enveloped viruses encode _____ that are inserted into ____ and direct formation fo the viral envelope upon release.

Answer 27

Glycoproteins
Lipid membranes

Question 28

How do viruses exit the cell?

Answer 28

Lysis of cell
Budding (extrusion from cell membrane)

Question 29

Enveloped viruses exit the cell by __

Answer 29

Budding