Lecture 2 1/25/24

Question 1

What are the steps of the viral replication cycle?

Answer 1

-adsorption/attachment
-entry
-uncoating
-synthesis of viral nucleic acids and proteins
-assembly/maturation
-release

Question 2

What are the two strands of DNA?

Answer 2

-coding strand: 5’ to 3’
-template strand: 3’ to 5’

Question 3

Which DNA strand is used to make 5’ to 3’ RNA?

Answer 3

template strand

Question 4

What are the characteristics of class 1 dsDNA viruses?

Answer 4

-majority replicate in host cell nucleus
-circular or linear genomes
-early proteins synthesized first
-late proteins synthesized last
-parasitize off of the host cell’s DNA polymerase machinery

Question 5

Which class 1 viruses do NOT replicate in the host cell nucleus?

Answer 5

poxviridae and asfarviridae

Question 6

What are the characteristics of class 1 polyomaviridae?

Answer 6

-circular genome
-small genome
-no viral DNA polymerase
-encode tumor antigens that modulate cell cycle

Question 7

What are the characteristics of class 1 adenoviridae?

Answer 7

-linear genome
-encodes DNA polymerase
-E1A proteins are powerful transcription activators

Question 8

What are the characteristics of class 1 herpesviridae?

Answer 8

-large linear genome
-encode complex replication system
-produce latent infection regulators
-can incorporate into host genome

Question 9

What are the characteristics of class 1 asfarviridae?

Answer 9

-large linear genome
-replicates in cytoplasm
-only dsDNA virus vector-transmitted by athropods

Question 10

What are the characteristics of class 1 poxviridae?

Answer 10

-large linear genome
-replicates in cytoplasm
-encodes complete DNA replication and mRNA synthesis system
-packaging and release leads to different forms
-encode numerous immune modulation genes

Question 11

What are the characteristics of class 2 ssDNA viruses?

Answer 11

-single-stranded linear or circular genome
-smaller genome
-rely on cells actively proliferating/in S phase
-replicate in cell nucleus
-first step of replication is producing complementary DNA strand
-both + and - sense DNA strands are produced, but only one is packaged into each virion

Question 12

What are the characteristics of class 2 circoviridae?

Answer 12

-small circular genome
-dependent on host cell machinery
-2 ORFs and differential mRNA splicing leads to two forms of replication protein

Question 13

What are the characteristics of class 2 parvoviridae?

Answer 13

-linear genome with 3’ and 5’ hairpins on either end
-dependent on host cell machinery
-2 ORFs and pre-RNA splicing
-replicate only in cells in S phase or those infected with helper virus

Question 14

What is reverse transcription?

Answer 14

synthesis of DNA from an RNA template

Question 15

What drives reverse transcription?

Answer 15

reverse transcriptase, an RNA-dependent DNA polymerase

Question 16

What are the characteristics of class 6 +ssRNA + RT viruses?

Answer 16

-genome is NOT used directly as mRNA
-each virion has 2 genome copies and a tRNA primer
-viral encoded enzymes are reverse transcriptase, protease, and integrase
-replicate in nucleus

Question 17

What are the steps of reverse transcription for a class 6 virus?

Answer 17

-RT synthesizes a piece of complementary ssDNA
-RT degrades RNA strand of the RNA-DNA hybrid
-RT makes a complementary strand to the first ssDNA strand to form dsDNA
-dsDNA genome can be inserted into the host genome

Question 18

Which class of viruses can lead to oncogenic cell transformation?

Answer 18

class 6 retroviruses