viruses n shii

• viruses are made up of:

  • nucleocapsid
  • genetic material that is either DNA or RNA
  • some have a lipid envelope
• capsid - protein outer coat
• genetic material is either DNA or RNA
• Capsid and genetic material is known as nucleocapsid
• some viruses have a nucleocapsid alone but as well as a lipid envelope
• viruses are divided into: either DNA or RNA, single stranded or double stranded
• bacteriophages size ranges from 25 nm to pox viruses w dimensions 400 x 240 x 200nm
• canine dimpster virus - single stranded Rna virus infecting dogs
• canine distemper virus affects big cats but not domestic cats
• diseases related to canine distemper : phoncine distemper virus, rinderpest, measles
• viruses are obligate intracellular parasites - they cannot exist outside of organic material
• virus replication requires components of host cell in order to replicate
• progeny refers to the decendant of offspring of a living organism which can be seen in virology where the virus uses the host cell to reproduce itself
• for both double standed and single standed DNA viruses:

  1. host RNA polymerase transcribes mRNA from viral DNA
  2. viral mRNA feeds into host protein synthesis mechanisms
  3. viral proteins produced allows enzymes and creation of new capsids for new virus particles
• double stranded RNA virus:

  1. viral RNA polymerase transcribes viral mRNA
  2. viral proteins created
  3. enzymes and new capsids formed for new viral particles
• positive sense ssRNA:

  1. viral genome acts as mRNA - feeds in hosts protein synthesis mechanisms
  2. viral proteins made
  3. enzymes and new capsids made for new viral particles
• RETROVIRUS - positive ssRNA:

  1. reverse transcriptase uses viral RNA as a template - makes negative sense ssDNA
  2. host enzyme copies and makes dsDNA and integrated into host genome and feeds into protein synthesis mechanisms
  3. viral proteins made
  4. enzymes and new capsids made for new viral particles
• negative sense ssRNA:

  1. viral RNA polymerase copies genome, acts as mRNA - feeds into host protein synthesis mechanisms
  2. viral proteins made
  3. enzymes and new capsids made for viral particles
• prions are small proteins (<100nm long), no nucleic acid and very slow replication
• prions cannot be cultured in the lab and does not cause an immune response in the host
• prions are almost impossible to remove from surfaces
• prions associated diseases:

  • kuru
  • scrapie
  • bovine spongiform encephalopathy
  • creutzfeldt-jakob disease
• winter viruses refer to viruses that spead more esily during the winter - these include respiratory and norovirus
• common cold caused by rhinoviruses - ssRNA, positive sense - or coronaviruses
• protozoa have 4 groups:

  • amoebae
  • flagellates
  • ciliates
  • sporozoans
• amoebae have 2 life cycle stages:

  • motile amoebae
  • resistant cyst
• motile amoebae move by extending psuedopodia and feeds by phagocytosis
• flagellates have flagellae used for movement with many free living species (esp in fresh water) and are some important pathogens of humans and animals
• ciliates:

  • characterised by the possession of cilia to aid movement
  • have micro and macronucleus
• micronucleus in ciliate involved in sexual reproduction
• macronucleus involved in transcription and cell growth functions
• sporozoa:

  • obligate parasites
  • complex life cycles w both sexual and asexual reproduction
  • contains important animal and human pathogens
• there are 5 parasites in humans which causes malaria with two of these causing the greatest threat
• plasmodium has complex life cycle involving mosquitoes as vectors
• malaria is caused by protozoa from sporozoan group plasmodium
• there is escherichia coli and entamoeba cole are two different pathogens
• seasonal influenza usually caused by type A and B but can also be cause by type C
• epidemic/pandemic flu is caused bu influenza A
• norovirus:

  • aka winter vomiting disease
  • positive sense ssRNA
  • diarrhoea and projectile vomitting
  • outbreaks in hospitals and care homes are common