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Flashcards in Lecture 1 Deck (36):

What is this lecture about?

Virus structure, classification and replication 


What are the 6 infections that have been implicated in cross-infection in dental surgery?

-Herpes Simplex Virus (HS) -Varicella zoster virus (VZV) -Human immunodeiciency virus (HIV) -Hepetitis B virus (HBV) -Hep C (HCV) -Hep Delta (HDV)


What are the implications of HPV in the oral cavity?

HPV infects the oral cavity and turned out to be one of the main causes of oral cancers.


Which one has greater risk given appropriate preccautions? patient or dentist?



What are some bacteria that causes dental infections?

Mycobacteria, Pseudomonas and legionella


What are the 5 bullet point characteristics mentioned in th lecture about viruses?

-Minuscule, acellular and infectious agents have both DNA OR RNA -Causes infections to humans animals and plants -Causes the majority of diseases plaguing the industrialized world -Cannot carry out any metabolic pathway -Neither grow nor respond to the enviroment.


What are the extracellular state characteristics for viruses?

-THe extracellular state is called Virion -Protein coat (capsid) surrounds nucleic acid -Nucleic acid and Capsid is called nucleocapsid - SOME have phospholipid envelop -the outer most layer provides protection and recognition sites for host cells.


What is the intracellular state?

-Capsid removed -The virus exists as nucleic acid interacting with viral and host protein


What are virions?

They're complete virus particles include nucleic acid, capsid and in some cases an envelope.


What is the morphology of capsids? 4 bullet points

-Provide protection for viral nucleic acid -provides Means of attachment to host's cells -Composed of proteinaceous subunits called "Capsomeres" -Capsomeres can be made out of one protein or multiple.


What are some viral shapes? How are they classified?

-They're classified by virion shape -Some basic shapes are helical, polyhedral and complex =


What is the VIral envelope and how do viruses acquire it? What is its composition?

-Acquired from host cell during viral replication or release -Envelop is a portion of membrane system of the host -Composed of proteins and phospholipids .-Some proteins virally coded glycoproteins (Spikes) -Envelope proteins and glycoproteins play role in host recognition.


What are the draw backs and the pros of having an envelope?

-Enveloped viruses are more fragile outside host -Enveloped viruses are less likely to be recognized and attacked by host system


How are viruses classified?

-Type of nucleic acid -Presence of envelope -Shape -Size Viral genra is recognized into families


What are the relative sizes of virions?

They're a fraction of the size of an ecoli bacteria which is a fraction of the size of a red blood cell.


What are the genetic materials of viruses?

-Maybe DNA or RNA viruses but never both Can be: -ssDNA -ssRNA -dsDNA -dsRNA May be: -Linear -segmented -single -circular


What is the Baltimore classification?

Viral mRNA HAS to be translated by host ribosomes always in (+ or-) strands. -The pathway the virus takes to generate mRNA defines the classes


What are the 7 classes of Viral genomes?

1) ds DNA 2) gapped ds DNA 3) ss DNA 4) ds RNA 5) ss (+) RNA 6) ss (-) RNA 7) ss (+) RNA with DNA intermediate


What are some ds DNA viruses examples?

-Adenoviridae -Herpesviridae -Papillomaviridae -Polymviridae -poxvirdae (DIFFERENT SHAPES CHECK OUT THE SLIDES)


What are some ss (+) RNA viruses?

-Picornaviridae (Polio and rhinovirus) -Calicviridae -Coronaviridae (SARS) -Flaviridae (yellow fever, westnile, hep C) -Reterovirus (HIV) -Togaviridae (Rubella Virus)


What are some examples of (-) ss RNA viruses?

-Paramyxoviridae (Measles and mumps) -Rhabdovirirdae (Rabies) -Filoviridae (Ebola virus, Marburg Virus) -Orthomyxoviridae (Influenza virus) -Arenaviridae (Lassa virus)


What are the main concept of Viral replication?

-Viruses are obligate intracellular parasites -They cannot grow outside of a suitable host cell since they require the host for various aspects of cellular metabolism to make up for their lack of gentic capacity -Depends on host cells and organelles to replicate and produce new virions


What are the 6 steps of the lytic cycle? What is the lytic cycle mean?

-Lytic means viral replication ends up lysing or killing the host cell Stages: 1) Attachment 2)Entry/ penetration 3)Uncoating 4) Synthesis/ replication 5) Assembly 6) Release Check the slide for the diagram and what each does


What is the replcation pattern of viruses? 


What are the replication patterns of animal Viruses?

1) Direct penetration




Will add the slide as soon as they're updated 


What are the replication patterns of Human/ Animal viruses, for ds DNA virsuse

For ds DNA viruses: 

  1. Similar to replication o cellular DNA
  2. Viral genome replicated in Nucleus
  3. Viral proteins are made in cytoplasm

Some exceptions

  1. Hep B virus replicate DNA from an RNA intermedia



Describe the ds DNA replication?

Its similar to cellular DNA replication

  1. Uses DNA dependent RNA polymerase to transcribe the (-) DNA strand into (+) RNA which is then translated into viral proteins 
  2. It can use DNA dependent DNA polymerase to make more copies of + and - DNA strands. 


What about the replication of ss DNA viruses? 

  1. Cells do not use ssDNA 
  2. Parvoviruses have ss DNA and fold on itself to make ds DNA. 
    1. This then leads to being replicated by DNA polymerase and either utilize DNA dependent RNA polymerase to make (+) RNA and translate virus proteins
    2. So unlike ds DNA viruses it has to go through the extra step of folding on itself to make a ds DNA in order to proceed to replication and translation 


How many types of RNA viruses are there? 

  1.  + ss RNA virus
    1. Retroviruses
  2. - ss RNA virus
  3. ds RNA virus 


How does the synthesis of RNA viruses differ from DNA viruses?

  1. They have to make or bring with them (RdRp) RNA dependent RNA polymerase 
    • Postive sense RNA can act as mRNA 
    • Negative-sense RNA has to make a positive copy first before it can translate itself  


What are some important factors of replication for RNA viruses? 

  1. They don't use their genomes as mRNA 
  2. They use DNA intermediary transcribed viral reverse transcriptase template to produce viral genomes. 
    1. So it has another extra step! 7 Steps 


Memorize the summary table for synthesis strategies of Animal virus 


What are the different assembly methods each class of viruses utilizes?

  1.  Most DNA viruses assemble in the nucleus 
  2. Most RNA viruses assemble in the cytoplasm
  3. The initial host health and virus type dictates the amount of replication
  4. Enveloped viruses are more problematic as they persistent in terms of infection
  5. Nake viruses leave via exocytosis or lysis 


What is the process of budding in enveloped viruses? 5 steps 


How does the pattern of abundance of virus (in persistent infections) look like on a graph of # of viruses vs time?


What does the concept of "Latency of viruses" mean? What are they called? (two names). And what is the duration of incorporation of virus in the host? 


  1. When viruses remain dormant in host cells
  2. Viruses are called latent or proviruses
  3. Maybe prolonged years without activity 
  4. Incorporation of provirus into host DNA is permanent