Lecture 14 - Virus Overview Flashcards Preview

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Flashcards in Lecture 14 - Virus Overview Deck (22):

Name the four genomes of viruses



The protein capsids have what two shapes



Cells release viruses be what two processes?

1.Budding process where each virus leaves in a membrane bubble that stays around the virus capsid (called an envelope). Envelope has spikes embedded
2.Lysis - viruses trigger cells to break open and release "naked" nucleocapsids. Spike proteins integrated directly into the capsid


*Viral infections may cause one of what five cellular outcomes

1.Abortive (no progeny viruses produced)
2.Lytic (acute process released by death of cell)
3.Chronic, Non-Lytic (infected cells slowly release viral progeny without cell death)
4.Latent (virus genome become integrated into cell DNA. It is dormant but may re-awake at anytime producing progeny)
5.Transformation (virus causes cell to proliferate uncontrollably)


What is a capsid

A protein shell that may be icosahedral or helical in shape. It encloses the genetic material


What is the difference between + and - strands of genetic material

+ is same orientation as mRNA
- is the anti-sense orientation


What are the spike proteins?

They are on the extreme outside of both enveloped and non-enveloped viruses. They determine what cells the viruses can infect. Spike mutations are important for expanding the range of potential hosts a virus might infect.


What are the four basic morphologies of viruses

1. Non-enveloped, naked icosahedral
2. Enveloped icosahedral
3. Non-enveloped, naked helical
4. Enveloped helical


What are the two keys for the virus to replicate and cause disease within a cell

1. Viruses must cause the replication of their genetic material
2. Viruses must produce positive-stranded mRNA (+RNA) to replicate their protein components


Quickly state the 6 steps of virus replication

1.Attachment via spike proteins on target cell
2.Penetrate into cell by endocytosis or cell membrane fusion
3.Virus uncoats protein capsid inside cell
4.Viral genome is exposed and replication of viral protein structures and genome occurs
5.New viral particles begin to assemble
6.Complete virus particles are released from cell through budding or cell lysis


Naked, non-enveloped viruses are usually released how from the cell?

Cell lysis


Most viral infections follow what type of growth curve?

Simple one-step growth curve


On the growth curve, define eclipse period and growth period.

Eclipse period: period of time during which the virus uncoats and begins replicating its individual constituents

Growth period: Constituents are assembled into many complete viral particles, the total number of which equal the yield


All viruses need to be able to synthesize what type of mRNA to effectively carryout their replication in a cell and why?

Positive-strand (+) mRNA
-Viruses 'hijack' a cell's normal mechanisms for translation of (+) mRNA into proteins.


Define Viremia

Release of viral agent into the blood


What is a viroid and what do they infect?

Infectious nucleic acid polymers that lack capsids. As far as is known, they only affect plants. No Humans


What is a prion and what do they infect?

Infectious agents that appear to be only protein. They only infect animals and humans we think


Describe difference between horizontal and vertical transmission of an infection

Horizontal - Individual to individual

Vertical - From mother to neonate


What is more common, horizontal or vertical transmission?

Horizontal transmission.


*Explain the iceberg concept of infectious disease

many infected individuals never show clinical signs or symptoms, with many if not most infections occurring 'below the waterline'. Polio is a good example with only .1 to 1 percent with a clinically apparent disease.


Understand that the number of microorganisms present in a patient must exceed a certain threshold to cause clinical disease.
-Asymptomatic infection
-Recovery and cure
-Recurrent illness

Just a fun fact from slide # 14 to not forget about...


****Make sure to understand the NA polymerases needed by viruses to replicate

ssDNA, dsDNA --> do not need to code for or bring a NA polymerase

(+) ssRNA --> Must code for NA polymerase but does not need to bring

(-)ssRNA, dsRNA --> Must code and bring an NA polymerase