Viruses, Viroids, & Prions Deck (E4)

Question 1

What are the 5 key viral features?

Answer 1

1) Obligate intracellular pathogen
2) Host range
3) Acellular
4) Nucleic acid
5) Protein coat (capsid)

Question 2

According to the International Committee on Taxonomy of Viruses (ICTV), what are the 3 factors determining a virion?

Answer 2

1) Developed, infectious, viral particle
2) Elementary bio-systems
3) Classified into orders, families, genera, and species

Question 3

What are the 4 primary means of classifying a virus?

Answer 3

1) Genome composition
2) Replication & mRNA expression
3) Capsid morphology
4) Host range

Question 4

When isolating and cultivating a virus, it must be grown in…

Answer 4

Living cells

Question 5

Phages are cultivated in { } cultures, forming { }.

Answer 5

1) Bacterial
2) Plaques

Question 6

Animal viruses were historically grown in…

Answer 6

Animals or embryotic eggs

Question 7

Animal viruses are NOW grown in…

Answer 7

Cell cultures (whether primary or continuous “HeLa” cell lines)

Question 8

Name the 2 methods used to identify virions.

Answer 8

1) Serological
2) Molecular

Question 9

Bacteriophages go through a lytic and lysogenic cycle. What is the difference?

Answer 9

Lytic - phage causes cell to burst and host cell dies

Lysogenic - phage incorporate into host genome

Question 10

Which cycle is a bacteriophage considered a prophage? Lytic or lysogenic?

Answer 10

Lysogenic

Question 11

Name the 5 steps of the bacteriophage lytic cycle (HINT: Amanda Pulled Brian’s Mother, Rhonda).

Answer 11

1) Attachment
2) Penetration
3) Biosynthesis
4) Maturation
5) Release

Question 12

What are 3 benefits to lysogeny?

Answer 12

1) Re-infection immunity
2) Phage/lysogenic conversion
3) Specialized transduction

Question 13

Explain the 2 key steps a DNA virus performs to multiply.

Answer 13

1) Use host DNA polymerase after viral genome enters cell to make more of itself

2) Use host RNA polymerase to form mRNAs that are translated into capsid proteins

Question 14

What is the difference between positive-sense ssRNA (+ssRNA) vs. negative-sense ssRNA (-ssRNA) viruses?

Answer 14

Positive-sense (coding) can be directly translated to protein while negative-sense (non-coding) has to be transcribed to positive-sense before translating to protein

Question 15

How do dsRNA viruses multiply?

Answer 15

The dsRNA unwinds into positive and negative-sense strands. Positive translates proteins. Negative polymerizes w/ positive via viral RNA polymerase to renature the dsRNA.

Question 16

How does a retrovirus multiply? List in 2 steps.

Answer 16

1) The RV’s RT converts its +RNA to dsDNA, which incorporates into host genome

2) Host RNA polymerase II transcribes viral DNA to RNA, which translates to more RT, glycoproteins, and capsid proteins

Question 17

What is the difference between naked and enveloped viral release?

Answer 17

Naked - exocytosis or lysis

Enveloped - budding

Question 18

What is the difference between latent and persistent viral infections?

Answer 18

Latent - remain dormant for a long time

Persistent - disease progresses over a long time

Question 19

What is the major difference between a virus and a viroid?

Answer 19

Viroids don’t have protein coats, and can only infect plants with defective membranes. Also, viroids can’t recognize healthy cells without the protein coat

Question 20

A proteinaceous infectious particle.

Answer 20

What is a prion?

Question 21

What type of disease does a prion cause?

Answer 21

Spongiform encephalopathy

Question 22

Name 4 diseases caused by prions.

Answer 22

1) Mad cow
2) Kuru
3) Scrapie
4) Creutzfelt-Jakob

Question 23

How does a regular cellular protein differ from an infectious prion?

Answer 23

Normal proteins tend to have 3 alpha helices and 1 beta sheet while infectious prions tend to have a higher beta-sheet content that causes improper protein folding, leading to brain issues