Viruses Flashcards
What are viruses?
Non living, lack cellular structure, don’t carry out cellular processes
Viruses must be in a host cell to produce
Viruses can be classified based on…
Disease they cause, size and shape, nucleic acid structure
Viruses that infect bacteria are called…
bacteriophages
Different shapes of viruses are…
Polyhedral, cylindrical, alien shape, spherical
2 types of nucleic structure are…
RNA viruses: more common, more errors during replication, higher mutation rates
DNA viruses: less common, less errors during replication, lower mutation rates
The lytic cycle
depends on the metabolism of the host cell to replicate DNA or RNA
Steps of Lytic cycle are..
Attachment: virus attatches to host cell and injects nucleic acid into cell
Synthesis: virus DNA takes over host cell and programs it to replicate its DNA
Assembly: All components of virus come together to create new virus particles
Release: Host cell breaks open and new virus particles are released. Host cell dies
Lytic cycle makes us feel..
sick! because of the bursting of cells which gives us symptoms and makes us feel bad
Lysogenic cycle
Virus is hidden in DNA until it wants to attack
Lysogenic cycle steps…
- Attachment: Virus attaches to cell, DNA enters and integrated itself into hosts cells DNA
- Reproduction: Virus DNA makes copies of itself during normal mitosis of the cell
- Cytokinesis: Daughter cells of mitosis have virus DNA integrated with their own and the cycle continues
Viruses can alternate between both the lysogenic cycle and lytic cycle. What virus alternates between the 2?
HIV has an enzyme that transcribes RNA to DNA. This DNA can then insert itself into host cell and make copies of itself as cell divides.
Example of virus going through lysogenic and lytic cycle?
Herpes: sores appear during lytic cycle when host cells are destroyed. but disappear during lysogenic cycle when viral DNA is incorporated into host cell DNA
Why are viruses important?
- Ability to spread
- Can cause epidemic or pandemic
- Some can increase cancer risk
- Kill crops and livestock
- in gene therapy you can kill cancer cells
What are vaccines?
Train our bodies to defend against the virus by injecting dead or weakened viruses into our bodies. Immune system will build antibodies against it
What are Prions?
Proteins found in all body tissues but at high levels in the brain. Only disease causing agents that don’t have DNA or RNA.
How can disease start from prions?
When prions(proteins) aren’t folded correctly and covert normal shaped proteins into a harmful shape. When prions get into our brain, proteins become misshaped and brain cells start dying.
HIV contains Reverse transcriptase, what does it do?
when RNA goes to DNA
Lysis
To burst
Lysogenic cycle only becomes active when..
change in environment
Retrovirusses
can alternate between lysogenic cycle and lytic cycle
Prions are found all over the body but highest in the brain
Prions are the only disease agents that don’t have…
DNA or RNA
Prions cause..
Crutezfeldt- Jakob Disease, which is related to mad cow disease
