Lecture 2 1/25/24 Flashcards
What are the steps of the viral replication cycle?
-adsorption/attachment
-entry
-uncoating
-synthesis of viral nucleic acids and proteins
-assembly/maturation
-release
What are the two strands of DNA?
-coding strand: 5’ to 3’
-template strand: 3’ to 5’
Which DNA strand is used to make 5’ to 3’ RNA?
template strand
What are the characteristics of class 1 dsDNA viruses?
-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
Which class 1 viruses do NOT replicate in the host cell nucleus?
poxviridae and asfarviridae
What are the characteristics of class 1 polyomaviridae?
-circular genome
-small genome
-no viral DNA polymerase
-encode tumor antigens that modulate cell cycle
What are the characteristics of class 1 adenoviridae?
-linear genome
-encodes DNA polymerase
-E1A proteins are powerful transcription activators
What are the characteristics of class 1 herpesviridae?
-large linear genome
-encode complex replication system
-produce latent infection regulators
-can incorporate into host genome
What are the characteristics of class 1 asfarviridae?
-large linear genome
-replicates in cytoplasm
-only dsDNA virus vector-transmitted by athropods
What are the characteristics of class 1 poxviridae?
-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
What are the characteristics of class 2 ssDNA viruses?
-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
What are the characteristics of class 2 circoviridae?
-small circular genome
-dependent on host cell machinery
-2 ORFs and differential mRNA splicing leads to two forms of replication protein
What are the characteristics of class 2 parvoviridae?
-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
What is reverse transcription?
synthesis of DNA from an RNA template
What drives reverse transcription?
reverse transcriptase, an RNA-dependent DNA polymerase
What are the characteristics of class 6 +ssRNA + RT viruses?
-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
What are the steps of reverse transcription for a class 6 virus?
-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
Which class of viruses can lead to oncogenic cell transformation?
class 6 retroviruses
