Viral Replication notes so far

IV. Viral Replication
a) Attachment – occurs through specific interaction between specific viral proteins (usually Glycolprotiens) and receptor on host cell – virus sticks to host cell/adsorption – Cell pulls in virion attachment 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.
i. DNA viruses: enzymes (viral) help get viral DNA into nucleus(eukaryotic viruses) and patch viral DNA into host chromosome (both eukaryotic viruses and bacteriophages)
ii. RNA viruses: have own enzymes that start copying RNA genome  more RNA – Use host tRNA, rRNA, amino acids to translate RNA genomes into proteins
iii. Retroviruses: have RNA genomes that is copied by viral enzyme reverse transcriptase to copy RNA genomes into DNA copies which are integrated into host chromosome just as if were a DNA virus. HIV is an example. Is copied by the backwards not RNA as well once copied to DNA then follows DNA not RNA even though is RNA genome.
d) Synthesis of viral proteins
- DNA virus: proteins transcribe and translated off of viral genes in viral DNA that’s not in host chromosome and copies of DNA genome are being made.
- RNA virus: RNA genome copied, RNA transcript translated by host ribosomes, tRNA, amino acids.
- Retrovirus – Going to be a mix of DNA and RNA virus. Initially copied into double stranded DNA then patched into host chromosome and then follows DNA coping sequence. (DNA version of viral RNA genome patched into host chromosome transcribed and translated; RNA copies of viral genome transcribed to be packaged to new virions.

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