november 20 notes

November 20, 2009—notes
Virion= single virus particle
1) Viral replication
a) Attachment/ adsorption
• Attachment: interaction between viral proteins (usually glycoproteins) and receptors on host cell
• Adsorption: cell pulls in virion attached to its surface
b) Penetration/ decoating
• Vacuole containing virion fuses with lysosome- lysosome has enzymes, low pH to break down proteins
 This breaks capsid up, freeing viral nucleic acid
c) Replication of nucleic acids
• Virions have nucleic acids and a few enzymes needed to start the host’s replication of their nucleic acids packaged in the viral capsids- these enzymes are also now free to help viral genome get replicated
 DNA viruses: enzymes (viral) help get viral DNA into nucleus (eukaryotic viruses) and patch viral DNA into host chromosome (both eukaryotic viruses and bacteriophages)
 RNA viruses: have own enzymes that start copying RNA which leads to more RNA
use host tRNA, rRNA, amino acids to translate RNA genomes into proteins
 Retroviruses: RNA genome that is copied by viral enzyme (reverse transcriptase) into double-stranded DNA copy—that DNA version of viral genome is then patched into host cell chromosome
d) Synthesis of viral proteins
• DNA virus: proteins transcribed and translated off of viral genes in viral DNA that is now in host chromosome and DNA copies of DNA genome made
• RNA virus: RNA genome copied, RNA transcript translated by host ribosomes, tRNA, amino acids
• Retrovirus: DNA version of viral RNA genome patched into host chromosome transcribed and translated; RNA copies of viral genome transcribed to be packaged into new versions