Test 3 - Viruses: General Introduction Flashcards
Viruses DO have
Genetic material surrounded by protein
Viruses DO NOT have
PM, organelles, or ribosomes
Living or Not: Is the Virus organized?
Yes.
Living or Not: Is this Virus able to Metabolize? Why?
Metabolic Activity/E do not exist outside the host because it lacks structure for metabolism, and uses host structures instead.
Living or Not: Is the Virus able to grow/develop?
No.
Living or Not: Does the virus reproduce?
Yes, in the host.
Living or Not: Is the virus able to interact and respond to the environment? Examples (2)?
Yes.
- Viruses can ∆ gene expression depending on the environment.
- Viruses must interact with cell surface to trigger infection.
Living or Not: Is the virus able to Evolve?
Yes.
Living or Not: Is the virus living?
No. Virus has property of life, but cannot reproduce/metabolize by itself, and hence is not life.
Viral Genome is different than Cellular Genome because…
It can be both RNA and DNA based. (Cells do not have RNA genome.)
Viral genome has 3 characteristics…
- DNA or RNA
- x1 or x2 stranded
- Linear or Circular?
Viral genome codes for 3 functions:
- Structure
- Reproduction
- Entry and Exit from Host
What is a Capsid? Is it present in all viruses? What is its subunit called?
Protein surrounding genome, present in all viruses, made of subunits named capsomere.
What is a Viral Envelope? Is it present in all viruses? What is it made of? How is it advantageous?
Membrane-like structure that surrounds the CAPSID, present in only some viruses. It is made up of viral proteins and host proteins, which aids in infection.
How does the Virus infect Host Cells? (6 Steps)
- Viral coat protein (capsid or viral envelope) binds to host cell receptor with high specificity.
- Virus enters cell
- Virus is uncoated (no more capsid/envelope)
- Virus is replicated. (Both genome and protein).
- Newly made genome and capsid assemble into virion through spontaneous reaction due to existing affinities.
- Virion is released from host cell.
Why does the host cell usually die after viral infection?
Lysis or lack of E/machinery absorbed during infection
Bacteriophage: What are they?
Viruses that infect bacteria only.
Bacteriophage: Structure includes…
Head, which includes the DNA, Tail Sheath, and Tail Fiber.
Bacteriophage: Which region allows attachment to host cells?
Tail
Bacteriophage: What is a Temperate Bacteriophage? What is a Virulent Bacteriophage?
Temperate Bacteriophage: Lytic and Lysogenic Cycle.
Virulent Bacteriophage: Lytic Cycle ONLY.
Bacteriophage Lambda: Is a (Temperate/Virulent) phage.
Temperate.
Bacteriophage Lambda: What effects whether it is in Lytic or Lysogenic Cycle? Explain the pre-requisites for the two conditions.
MOI, or # of phages entering the cell.
- ++MOI: Lysogenic Cycle
- – MOI: Lytic Cycle.
Bacteriophage Lambda: In which cycle is it utilizing its ability to regulate gene expression? When is it expressing all genes?
Lysogenic– viral genes replicated but silenced. Lytic cycle is when phage expresses ALL genes.
Bacteriophage Lambda: Explain how it infects the cells. What part of the process is different from the general process discussed before?
- Viral coat protein (capsid or viral envelope) binds to host cell receptor with high specificity.
- VIRAL DNA ENTERS THE CELL
- Virus is NOT UNCOATED (no capsid)
- Virus is replicated. (Both genome and protein).
- Newly made genome and capsid assemble into virion through spontaneous reaction due to existing affinities.
- Virion is released from host cell.
