Chapter 19 - Viruses

Question 1

Viruses are known as….

Answer 1

Obligate intracellular parasite

Question 2

What does a virus’s genome consist of?

Answer 2

DNA or RNA not both, single or double stranded

Question 3

All viruses have ___________ and ___________

And some have __________ and ___________

Answer 3

Genetic material, a protein code

Some have an envelope, spikes (glycoprotein)

Question 4

Neucloapsid

• Virus genome = nucleic acid core
• capsid (made up of capsomeres)

Viruses can be enveloped or ___________

Answer 4

Naked

Question 5

What determines the shape of a virus?

Answer 5

Capsid and or envelope determine shape

Question 6

Some viruses have membraneous envelopes that help them affect hosts along with _______

This is done by a ___________ mechanism

Answer 6

Spikes

“Lock and key”

Question 7

Viral envelopes surround the ___________ of influenza viruses and many other viruses found in animals

Envelopes are derived from the host cells membrane, contains a combination of viral and host cell molecules

Answer 7

Capsids

Question 8

What are viruses called that infects bacteria?

They have the most complex capsids found among viruses

The host cell must have a receptor for this virus to attach

Answer 8

Bacteriophages

Question 9

Each virus has a ___________, a limited number of host cells it can infect

Answer 9

Host range

Question 10

Viral specificity determines….

Viruses bind/recognize host receptor molecules

Example, HIV targets human T-helper cells

Answer 10

Host range

Question 11

• phages are the best understood of all viruses

- they just have what two reproductive mechanisms?

Answer 11

The lytic cycle and the lysogenic cycle

Question 12

What are the steps of viral a replication cycle? ***

Answer 12

1. The virus enters the cell and is uncoated, releasing viral DNA and capsid proteins
2. Host enzymes replicate the viral genome
3. Meanwhile, host enzymes transcribe the viral genome into viral mRNA, which host ribosomes use to make more capsid proteins
4. Viral genomes and capsid proteins self assemble into new virus particles, which exit the cell

Question 13

What kind of viruses can do the lytic cycle or the lysogenic cycle?

Answer 13

Temperate virus

Question 14

A phage replicative cycle that accumulates in the death of the host cell

Produces new phages and lyses the host cell wall, releasing progeny viruses

Answer 14

The lytic cycle of phage T4

Question 15

A phage that reproduces only by the lytic cycle is called a….

Answer 15

Virulent phage

Question 16

Bacteria have defenses against phages, including ____________ that recognize and cut up certain phage DNA

Answer 16

Restriction enzymes

Question 17

When the viral DNA molecule is incorporated into the host cells chromosomes
Replicates the phage genome without destroying the host

Every time the host divides, it copies the phage DNA and passes the copies to daughter cells

Answer 17

The lysogenic cycle

Question 18

The integrated viral DNA that happens in the lysogenic cycle is called?

Answer 18

Prophage (viral plus bacterial DNA)

Question 19

And environmental signal can trigger the virus genome to exit the bacterial chromosome and switch to the ______ mode

Answer 19

Lytic

Question 20

Phages that use both the lytic and lysogenic cycle‘s are called….

Answer 20

Temperate phages

Question 21

What are the two key variables used to classify viruses that infect animals?

Answer 21

• DNA or RNA

- single-stranded or double stranded

Question 22

Many viruses that infect animals have a…

The phospholipid bilayer can fuse with the host

Viral glycoproteins on the envelope bind to specific receptor molecules on the surface of a host cell

Answer 22

Membraneous envelope

Question 23

Some viral envelopes are formed from the host cells plasma membrane as a viral capsids exits

Other viral membranes form from the house nuclear envelope that are then replaced by an envelope made from…

Answer 23

Golgi apparatus membrane

Question 24

The broadest variety of RNA genome’s is found in viruses that infect….

Answer 24

Animals

Question 25

What are viruses called when they use reverse transcriptase to copy their RNA genome into DNA

Answer 25

Retroviruses

HIV is the retro virus that causes AIDS

Question 26

HIV is considered both a __________ and a ___________

Answer 26

Provirus, retrovirus