High School
SAT
ACT
University
MCAT
LSAT
DAT
Wize University Biology Textbook > Viruses

Viral Infections & Hosts

Viral Morphology and DiversityPrevious Section
Prions & Viroids [Content coming soon]Next Section
Popular Courses
Find My Course
0:00 / 0:00

Viral Infections

This is a major issue in dense populations. Issues with COVID-19 are the result of a coronavirus that has mutated and now infects humans.
  • Viruses can not replicate without infecting hosts

  • Host: the organism infected with the virus
  • Host Range: number of different species a virus can infect
  • Most viruses only infect a single host species (specialist) Example: Measels Virus only infects humans
  • Some viruses have a wide range of hosts (generalist) Example: West-Nile Virus can infect Mosquitos, Birds, Humans etc.


PAGE BREAK

Viral Replication

  • Virus attaches to the outside of host cell
  • Virus injects nucleic acid into host
  • Virus hijacks the cell machinery to replicate its own components
  • Viral components come together to form new viruses
  • Virus is ejected from cell to infect other hosts
  • Lytic Cycle: the final step in viral replication bursts open and kills host cell
  • These types of viruses are virulent phages
  • Lysogenic Cycle: viruses do not kill host cell
  • Virus genes continue to be produced by host cell
  • Temperate phages alternate between lytic and lysogenic cycles

Photo by CNX OpenStax | CC BY
checklist
Mark Yourself Question
  1. Grab a piece of paper and try this problem yourself.
  2. When you're done, check the "I have answered this question" box below.
  3. View the solution and report whether you got it right or wrong.

Practice: Viruses

Describe the main difference between a lytic cycle and a lysogenic cycle.

Practice: Viruses

What does a virus's host range describe?

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?
Which of the following best describes how the Human papillomavirus can cause cervical cancer without causing mutations in any coding regions?
Briefly describe the lytic cycle of a virus.
Briefly describe the lytic cycle
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
Which of the following best describes how the Human papillomavirus can cause cervical cancer without causing mutations?
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
On the left (below) is an experimental drug, which is a nucleoside analogue. On the right is adenosine. The drug is used to treat RNA viruses (viruses that have RNA rather than DNA as their genetic material), such as Ebola. How do you think this works?