Micro Exam 2c

Question 1

characterizing a virus

Answer 1

• obligatory intracellular parasites
• contain DNA or RNA
• contain protein coat
• some are enclosed by envelope
• have spikes
• infect only specific types of cells

Question 2

morphology of virus

Answer 2

• polyhedral (icosahedrons)
• helical
• enveloped
• complex (bacteriophage)

Question 3

viral species

Answer 3

group of viruses sharing the same genetic information and ecological niche

Question 4

culturing bacteriophages

Answer 4

form laques on lawn of bacteria

- high specificity

Question 5

culturing animal and plant viruses

Answer 5

may be grown in cell culture

• newly-isolated cells
• continuous cell lines

Question 6

newly-isolated cells

Answer 6

grown in medium for only several generations is a primary cell culture

Question 7

continuous cell lines

Answer 7

may be maintained indefinitely, they are transformed

Question 8

virus identification

Answer 8

• cytopathic effects
• serological tests
• nucleic acids

Question 9

lytic cycle

Answer 9

causes lysis and death of cell

• attachment
• penetration
• biosynthesis
• maturation
• release

Question 10

lysogenic cycle

Answer 10

• prophage DNA incorporated into host DNA
• phage conversion
• specialized or generalized transduction

Question 11

multiplication of DNA viruses

Answer 11

• virion attaches to host cell
• enters cell and it’s DNA is uncoated
• portion of viral DNA is transcribed, producing mRNA that encodes early viral proteins
• viral DNA is replicated, and some more viral proteins made
• late translation and capsid proteins are synthesized
• virions mature
• virions released

Question 12

multiplication of + ssRNA

Answer 12

can directly synthesize the proteins required and replicate

Question 13

multiplication of - ssRNA

Answer 13

• must transcribe a + strand RNA

- + strand RNA serves as template for translation

Question 14

multiplication of dsRNA

Answer 14

• mRNA created within the capsid and then released into the cytoplasm

Question 15

host range

Answer 15

refers to spectrum of host cells in which a virus can multiply
- determined by specific attachment site on surface of host cell

Question 16

what is the capsid composed of?

Answer 16

capsomeres which can be a single type of protein or several types

Question 17

entry of animal viruses

Answer 17

endocytosis or fusion

Question 18

exit of animal viruses

Answer 18

budding or rupture in the cell

Question 19

multiplication of a retrovirus

Answer 19

• RNA is transcribed into DNA by reverse transcriptase
• the viral DNA is then transcribed into the RNA again, but lacks introns this time
• RNA is translated into protein

Question 20

ocogenic viruses

Answer 20

viruses that are capable of producing tumors

- only RNA viruses that are retroviruses seem to be oncogenic

Question 21

latent viral infections

Answer 21

viruses remain in asymptomatic host cell for long periods

- cold sores or shingles

Question 22

persistent viral infection

Answer 22

disease process occurs over a long period of time and are generally fatal

Question 23

prions

Answer 23

infectious proteins, degenerate brain tissue

- cause CJD and mad cow

Question 24

entry of plant virus

Answer 24

must enter plant hosts through wounds or with invasive parasites
- can also multiply in insect (vector) cells

Question 25

viroids

Answer 25

infectious pieces of RNA that cause some plant disease

- potato spindle tuber disease