Chapter 8: Viruses and Virology

Question 1

Virion

Answer 1

Extracellular form of a virus

Inanimate

Question 2

Virus structure

Answer 2

Nucleic acid surrounded by protein coat

Sometimes lipid envelope is present

Question 3

3 methods of horizontal gene transfer

Answer 3

Transformation
Transduction
Conjugation

Question 4

Transformation

Answer 4

Transfer of genetic materials from the environment

Question 5

Transduction

Answer 5

Transfer of genetic materials through mediators, esp viruses like bacteriophages

Question 6

Conjugation

Answer 6

Direct transmission of genetic materials from one bacteria to another through pilus

Question 7

Steps of viral life cycle (5 steps)

Answer 7

1. Attachment (adsorption) of the virion to the host cell
2. Penetration (entry, inspection) of the virion nucleic acid into the host cell
3. Synthesis of virus nucelic acid and protein by host machinery
4. Assembly of capsids and packaging of viral genomes into new virions
5. Release of virions from cell

Question 8

Titer

Answer 8

Number of infectious virions per volume of fluid

Question 9

Plaques (what are they, what do they determine)

Answer 9

spread mixture of molten agar, bacterial cells, diluted phage suspension onto nutrient agar plate
areas of cell lysis, plaques form
can be used to determine titers

Question 10

Temperate viruses

Answer 10

Enter stable relationships with host cells

Question 11

Lysogeny

Answer 11

Virus genome is replicated in synchrony with host chromosome

Question 12

Retroviruses

Answer 12

Infect with RNA
Use reverse transcriptase to make dsDNA from RNA
dsDNA integrates with host genome
normally fundctioning transcriptional machinery creates viral mRNA

Question 13

Poliovirus

Answer 13

Binds to CD155 receptors
Enters cell through endocytosis
ssRNA is directly translated as mRNA
Cell lyses