13 - Viruses

Question 1

Name and describe the 2 parts of viruses that ALL viruses have

Answer 1

1. nucleic acid (DNA or RNA; single or double; linear or circular)
2. capsid

Question 2

What is the 3rd part that SOME viruses have but not all?

Answer 2

envelope (lipid bi-layer; looks similar to plasma membrane; usually an envelope comes with spikes)

Question 3

Capsid

Answer 3

protein coat, 1+ types protein - different arrangements and capsomere subunits - determines shape of virus

Question 4

What are the 3 shapes of viruses?

Answer 4

1. helical (long rod, rigid/flexible) - rabies/Ebola
2. polyhedral (many sides) - polio/cold
3. complex (complex structures) - bacteriophages

Question 5

What virus part determines its shape?

Answer 5

capsid

Question 6

What can we use to grow viruses in a lab?

Answer 6

have to use a host

for example bacteriophages need to be grown inside bacteria

Question 7

What are the different methods for growing animal viruses in the lab?

Answer 7

1. living animals
2. embryonated eggs
3. cell cultures

Question 8

Steps of the bacteriophage replication cycle

Answer 8

1. attachment
2. penetration
3. biosynthesis
4. maturation
5. release

Question 9

Lytic cycle of bacteriophage

Answer 9

host cell dies (host cell lyses to release viruses)

Question 10

Lysogenic cycle of bacteriophage

Answer 10

host cell survives (virus integrates into host chromosome)

Question 11

Animal virus multiplication:

Answer 11

attachment -> entry -> uncoating -> biosynthesis -> maturation -> release

Question 12

Attachment of the animal virus replication cycle

Answer 12

1. envelope viruses use spikes
2. non-envelope viruses uses corners of the capsid

Question 13

How do viruses achieve ENTRY into an animal cell?

Answer 13

receptor-mediated endocytosis (plasma membrane folds in, vesicles) - the envelope is left behind at the host cell membrane

Question 14

What is being uncoated when a virus enters an animal cell?

Answer 14

the coat is being degraded - the nucleic acid is separated from protein coat

Question 15

What two parts does the virus need to make in an animal cell for biosynthesis?

Answer 15

1. nucleic acid
2. capsid protein

Question 16

Biosynthesis for DNA viruses:

Answer 16

1. DNA -> RNA -> protein (capsid)
2. DNA -> DNA (nucleic acid)

Question 17

Biosynthesis for RNA viruses:

Answer 17

1. RNA -> complimentary RNA -> original RNA (nucleic acid)
2. RNA -> protein (capsid)

Question 18

Biosynthesis for retroviruses

Answer 18

1. RNA -> DNA
2. DNA integrates into host DNA
3. DNA -> RNA -> protein

Question 19

What allows for retroviruses to convert RNA to DNA?

Answer 19

reverse transcriptase

Question 20

When a virus enters an animal cell, what happens during maturation?

Answer 20

assembly of all the parts made in biosynthesis

Question 21

How does release occur after maturation has been completed?

Answer 21

1. envelope: buds releasing of virus into envelope
2. non-enveloped: rupture of plasma membrane releases viruses

Question 22

Oncogenes

Answer 22

genes that can cause cancer when over-activated (normally turned off after birth)

Question 23

Tumor suppressor genes

Answer 23

genes that control unregulated cell growth (normally turned on)

Question 24

Oncogenic viruses

Answer 24

induce tumors, 10% cancers are virus related - genes within the virus lead to uncontrollable cell division or interfere with tumor suppressor/oncogenes (i.e. HPV/EBV)

Question 25

Latent viral infection

Answer 25

virus remains integrated in the host genome (herpes, chickenpox) - will become activated by weak immune system, stress, etc.

Question 26

Persistent viral infection

Answer 26

effects of virus infection occurs gradually over long period

Question 27

Acute viral infection

Answer 27

short-term (lots of virions at once)