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Wize University Biology Textbook > Viruses

Viral Morphology and Diversity

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Viral Morphology and Diversity

Viruses present complicated issues in biology. Are they living? are they just molecules? Did they evolve before or after bacteria?
  • Viruses: infectious particles made up of nucleic acid and a protein coat
  • Extremely small and simple particles
  • Not exactly living, but not simply a chemical
  • Have variable types of nucleic acid
  • Double-stranded DNA
  • Single-stranded DNA
  • Double-stranded RNA
  • Single-stranded RNA
  • Viruses are named after the type of nucleic acid (DNA virus or RNA virus)
  • Some viruses have as few as 4 genes others have hundreds
  • Capsid: protein shell around nucleic acid
  • Rod-shaped Example: Tobacco Mosaic Virus
  • Polyhedral Example: Adenovirus
  • Complex Examples: Influenza and Bacteriophage


Photo by Thomas Splettstoesser | CC BY . Photo by Victoramuse | CC BY


Practice: Viruses

What type of nucleic acid do viruses contain?

Practice: Viruses

The capsid forms a
shell around
in viruses.

Extra Practice
The HIV virus has an RNA genome but is classified as a retrovirus because viral enzymes reverse transcribe the viral RNA into DNA that inserts into the host genome. A molecule called AZT is a nucleoside mimic often used as an antiviral drug against this step in HIV's replication cycle. Which statement below best describes how HIV might evolve resistance to AZT?
What material is the capsid made out of?
Three main features include
nucleic
acid (DNA or RNA),
capsid
(or the protein shell), and the
envelope
(which is a layer of the membrane - on only some viruses).
Viruses have been shown to be related to cancer when they get incorporated into the genome of host cells. Which of the following is most likely to result in uncontrolled cell growth?
The virus expresses a miRNA that specifically targets a tumor suppressor gene
The virus expresses a gene that activates the host cells survival and proliferation pathway
From Term Test 2 Prep: Why are viruses not considered "alive"?
From Term Test 1 Prep: The HIV virus has an RNA genome but is classified as a retrovirus because viral enzymes reverse transcribe the viral RNA into DNA that inserts into the host genome. A molecule called AZT is a nucleoside mimic often used as an antiviral drug against this step in HIV's replication cycle. Which statement below best describes how HIV might evolve resistance to AZT?
Viral Evolution
Which of the following statements is TRUE regarding the use of antiviral therapies?
Why are viruses not considered to be alive?
i. They cannot reproduce on their own
ii. They lack the metabolic machinery to provide energy for themselves
Why are viruses not considered to be alive?
i. They cannot reproduce on their own
ii. They lack the metabolic machinery to provide energy for themselves
Put the following in order of size from LARGEST to SMALLEST:
Virus, nucleus, bacteria, eukaryotic cell, ribosome