Viruses Review
A virus is like a building contractor who has blueprints, but no building materials. Explain this statement.
Are Viruses Living Things? Are made of cells Can reproduce Contain genetic material Grow and develop Obtain and use materials and energy Respond to the environment Maintain homeostasis As a group, change over time X X √ X X X X √ Are Viruses Living Things?
Viruses are not considered to be living because: 1. They use a host cell for energy 2. They use a host cell for replication
Viral Structure Viruses have a simple structure: genetic material (DNA or RNA) a protein coat called a capsid that surrounds the genetic material Sometimes they have an envelope outside of the capsid (made of lipids and proteins).
Name tells you this virus infects bacteria
Name tells you this virus causes influenza
Viral size http://learn.genetics.utah.edu/content/begin/cells/scale/
Activity: Cell,Virus, or Both? Contains nucleic acid as genetic material
Activity: Cell,Virus, or Both? Can grow and develop
Activity: Cell,Virus, or Both? Can only replicate in a host
Activity: Cell,Virus, or Both? Can reproduce on its own
Activity: Cell,Virus, or Both? Obtain and use materials and energy
Activity: Cell,Virus, or Both? Respond to the environment
Activity: Cell,Virus, or Both? Maintain homeostasis
Activity: Cell,Virus, or Both? Can contain DNA
Activity: Cell,Virus, or Both? Which is smallest?
Activity: Cell,Virus, or Both?
Activity: Cell,Virus, or Both?
Viruses vs. Cells Characteristics of Viruses only Characteristics of Cells only How viruses & cells are alike
How do viruses infect cells? Once inside the host cell, one of two different processes can occur: Lytic cycle Lysogenic cycle
A. Lytic Cycle: Viral DNA enters a cell, reprograms the cell to makes copies of the virus, and causes the cell to burst releasing new viruses.
B. Lysogenic cycle: A virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cell DNA. Lysogenic infections may become lytic if the viral DNA leaves the host DNA.
DNA Viruses vs. RNA Viruses do not mutate frequently because they utilize the host cell's DNA polymerase to make more copies of the viral DNA. DNA polymerase can proofread and correct errors (mutations) during DNA replication. You only need a vaccine for a DNA virus once. Examples: smallpox, HPV (warts, cancers).
DNA Viruses vs. RNA Viruses have a high mutation rate when the cell copies RNA for new viruses, the enzyme used cannot proofread and fix mutations. Examples: Influenza, common cold virus (rhinovirus).
DNA Viruses vs. RNA Viruses Some RNA viruses use their RNA to make DNA - called retroviruses. When retroviruses make a copy of the RNA as DNA, the DNA can integrate into host cell DNA causing a lysogenic infection. Example: Human Immunodeficiency Virus (HIV).