Biology notes: Viruses

RNA

• RNA- Different type: mRNA and rRNA
• RNA is a molecule (transcriptase) enzyme
  
• Ribonucelic acid, generic translator
• DNA is double stranded, make new cells, makes protein
• RNA comes from DNA (transcribed into)
• mRNA (messenger) carries information somewhere to be used
• Ribosomes: proteins/rRNA--> main function make protein
• rRNA is like a translator, it reads the mRNA and tells the ribosomes how to make proteins

Retroviruses

• RNA virsuses that have a DNA stage
• Converts RNA -> DNA and DNA integrates into a host genome.
• Usually DNA-> RNA but viral RNA-> viral DNA
• Which makes ribosomes new viruses. Examples such as HIV.

1. Attachment
2. Entry
3. Reverse transcription
4. Biosynthesis
5. Maturation
6. Release
   

Viral evolution

• Believed that viruses evolved early& parasites of all 3 domains
• More closely related to host, viruses evolved from the host cell
  
• Viruses have small genomes, 4-100 genes 25%
• Mutatation: treatments needed to be changed, ex: influenza virus
• Antibiotics have no effect, treatments must target virus specific proteins/processes
• Many associated with cancer (promote cancer) human ppv
• integrate into host genome and disrupts host cell function
• Emerging viruses: viruses that have only recently caused disease
• Examples: HIV, SARS, west nile encephalitis, hantavirus
• Viral mutation, becomes more nasty or jump hosts such as avian flu

Viroids

• Similiar to a virus but has no capsid (protein jacket) just a naked RNA
• Infected plants-- extensive damage & millions of money/crops lost

Prions

• Wrongly shaped protein, infectious misfolded protein
• Shape is function, wrong function = death
  
• Deposites in brain causes degenerative brain diseases (spongiform encephalopathies)
  
• Mad Cow Disease
  
• Creutzfeld-Jakob disease
• Kuru (eating brains of their elders, eating prions now going to be in your brain, causing it to misfold, basically enters your body by eating it)