Viruses

Question 1

What is a virus (aka virion)?

Answer 1

A genetic element Replicate independently of host’s chromosome but not the host itself 1. can survive outside of a cell for long periods of time (composition and coating) 2. must attach and enter (infect) a host cell 3. hijack host cells’ machinery to replicate themselves 4. exit and transmission

Question 2

Which domains can viruses infect?

Answer 2

All of them

Question 3

What percent of the human genome is comprised of viral DNA?

Answer 3

8%

Question 4

Naked virus

Answer 4

Nucleic acid (DNA or RNA) surrounded by protein coat (capsid); no lipid

Question 5

Enveloped virus

Answer 5

coat + lipid bilayer (allows fusion w/ host)

Question 6

Viroids

Answer 6

Infectious nucleic acid with no protein coat (devoid of a coat)

Ex. potato spindle viroid (around 1960s)

Question 7

Prions

Answer 7

Infective proteins

eg. mad ocw or Creutzfeldt-Jakob

incorrectly or abherrantly folded proteins

Question 8

What is the genome of a viroid like?

Answer 8

Tiny and small, but has the highest per site mutation rate of all biological entities

Question 9

Hemi-fusion

Question 10

Envelope Fusion

Question 11

Endocytosis

Answer 11

Question 12

T4 bacteriophage

Answer 12

Useful in transduction

Question 13

Measles and RSV enter through which method?

Answer 13

Budding

Question 14

Synthetic Virus Drug Delivery system

Answer 14

Question 15

Bacteriophage: Lytic Cycle

Answer 15

causes lysis: virulent phage

Phage quickly replicates, kills host cell

generally lytic when host cell conditions are good

bacteria divide quickly but phage replicates even faster

or conditions are unfavorable (eg cell damaged)

top in picture

Question 16

Lysogenic cycle (bacteriophage)

Answer 16

(genic –> genome) temperate

Phage is quiescent

may integrate into host cell genome

replicates during host cell division

generally lysogenic in moderate cell conditions

phage can reactivate to become lytic kill host

Question 17

What are viruses classified by?

Answer 17

by genome structure and polymerase type

Question 18

Baltimore virus classification

Answer 18

emphasizes the form of the genome (DNA or RNA, single or double) and the route to generate messenger RNA

Question 19

Retroviruses

Answer 19

use a reverse transcriptase to copy their genomic sequence into DNA for insertion in the host chromosome

Question 20

Virus to bacteria ration

Answer 20

1: 100 in marine and aquatic environment
1: 1000 in soils