Virus and Phage 1

Question 1

Explain some differences between viruses and living organisms

Answer 1

Viruses: acellular, rely on host for energy
Living: can generate energy from the environment, cells can increase and grow

Question 2

Viruses of prokaryotes typically inject ___ into host cells

Answer 2

Genetic materials

Question 3

What is the primary difference between lytic viruses and temperate viruses?

Answer 3

Temperate viruses induce the lytic cycle

Question 4

What unit is used to count bacteria?

Answer 4

Colony forming units (CFU)

Question 5

Describe some DIRECT approaches to enumerating virus particles

Answer 5

Electron microscope

Viral genome via quantitative PCR

Question 6

Describe some INDIRECT approaches to enumerating virus particles

Answer 6

Hemoglutination assay 
Plaque assay (LD50)

Question 7

What two components do the simplest form of viruses have?

What are these viruses called?

Answer 7

Nucleic acid genome + protein shell (capsid)

Nucleocapsids

Question 8

(T/F) The protein shell of viruses are assembled from a few individual protein subunits

Answer 8

False!

Formed from many (hundreds) individual protein subunits

Question 9

The capsid head is formed from (#) protein subunits, which assemble into ___ and ___ (think soccer ball)

Answer 9

One
Hexagons
Pentagons

Question 10

Inside the capsid head the ___ looks like a thread on a spool

Answer 10

dsDNA

Question 11

What are the two general types of virions?

Answer 11

Non-enveloped

Enveloped

Question 12

(T/F) Enveloped viruses have plasma membranes composed of lipids

Answer 12

True!

Question 13

(T/F) Viral genomes can be RNA or DNA

Answer 13

True!

Question 14

(T/F) Viral genomes can only be single-stranded (ss) nucleic acids

Answer 14

False!

Can be single stranded (ss) or double stranded (ds)

Question 15

(T/F) Viral genes may be on a single nucleic acid molecule OR divided among multiple nucleic acid molecules

Answer 15

True!

Question 16

(T/F) Viral genomes do not vary greatly in size

Answer 16

False!

They can be anywhere from 4 kb long up to 1.2 mbp long

Question 17

What are the 6 minimum functions that a virus must do to reproduce?

Answer 17

1. bind to host cell
2. induce genome into host cell
3. get viral genome replicated
4. get viral proteins expressed
5. assemble new visions
6. get progeny virus to exit cell

Question 18

How do DNA viruses replicate their genome?

How do RNA?

Answer 18

They have proteins that hijack the host DNA polymerase

They provide their own protein to replicate the RNA

Question 19

How do DNA viruses get their viral proteins expressed?

How do RNA?

Answer 19

They often use host RNA polymerase to synthesize mRNA

They provide their own protein to synthesize mRNAs

Question 20

(T/F) During translations, viral mRNAs are translated by host ribosomes

Answer 20

True!

Question 21

What are two ways that virus progeny can leave the host cell?

Answer 21

1. lysing of the cell

2. budding through the hosts’ plasma membrane