Intro To Viruses- Lecture 10/20/21

Question 1

Process of viral infection (4 steps)

Answer 1

1- Attachement to surface receptors
2- Expression of viral genes
3- Genome replication
4- Assembly and egress

Question 2

Virions

Answer 2

Infectious unit of the virus, can make 100s in one cell

Question 3

Basic virion structure

Answer 3

• Nucleic acid genome
• Capsid (protein shell)
• Viral attachment proteins

Question 4

Envelope

Answer 4

Lipid surrounding that contains all other parts, sensitive to detergent (Some viruses)

Question 5

Naked Virus

Answer 5

Does not have an envelope

Question 6

Two structures of the capsid

Answer 6

• Icosahedral

- helical

Question 7

Gp41/gp120 and CD4 interaction

Answer 7

How HIV viruses get into helper T cells

Question 8

Neutralizing antibody

Answer 8

Can block attachment or fusion

Question 9

Two routes of fusion

Answer 9

1) fusion at plasma membrane (enveloped)

2) fusion in endosome (enveloped or non enveloped)

Question 10

Viral DNA genomes (4)

Answer 10

-Linear double stranded
-Linear single stranded
Circular, single stranded
Circular, double stranded

Question 11

RNA viral genomes (4)

Answer 11

• Linear plus stranded
• Linear minus stranded
• Segmented minus stranded
• Segmented double stranded

Question 12

Genomes that can be used without processing

Answer 12

• Linear ds DNA
• Circular ds DNA
• Linear plus stranded RNA

Question 13

Process for ss DNA to be transcribed (2 steps)

Answer 13

1- Turned to double by DNA pol

2- Transcribed by RNA pol

Question 14

How double stranded RNA and minus stranded RNA get transcribed

Answer 14

Need to encode for an RNA dependent RNA polymerase that is packaged in the virion

Question 15

Ways to encode multiple proteins on one RNA (5)

Answer 15

1- Segmented genome (different RNAs)
2- Polyprotein (cleave at the end of translation)
3- Nested mRNAs (Different proteins at different points)
4- Start and stop transcription (Different start and stop sites)
5- alternative. Splicing

Question 16

Unusual methods of translation

Answer 16

• Leaky scanning (May miss a start codon)

- Ribosomal frameshift (ribosome may miss a codon)

Question 17

DNA genome method of replication

Answer 17

Use cellular enzymes

Question 18

RNA genome replication

Answer 18

Always use virally encoded enzymes