Viruses: the itty bitty stalkers of doom!

ARE VIRUSES ALIVE? NO!

…WHY NOT? Viruses are infectious particles that contain DNA or RNA and a protein coat called a capsid They are not living because they DO NOT: Grow Reproduce on their own Obtain or use energy Respond to their environment

Structure Capsid = protein coat DNA or RNA = genetic material Capsids can have many different shapes!

SO HOW DO THEY INFECT US? Viruses can be considered a “borrowed life” They infect cells and use the cell’s machinery and parts to help them reproduce Viruses can infect humans, animals, plants, and bacteria.

HOW DO VIRUSES REPRODUCE IF THEY ARE NOT ALIVE?! The virus attaches to a host cell The virus’s genetic material (DNA or RNA) enters the host cell The virus’s genetic material causes the cell to make viral protein and genetic material New viruses form inside of the host cell New viruses are releases when the cell bursts Viruses need a host cell to reproduce because they are NOT living!!!!

HOW DO VIRUSES MUTATE? Sometimes during the process of copying the DNA or RNA of the virus, small errors occur in the copy. Most of the time, the change kills the virus and causes it to stop multiplying. However, sometimes the mutation can instead result in a changed protein that can replicate better and become more infectious Sometimes during the process of copying the RNA or DNA of the virus, small errors (substitutions in nucleotide base pairs) occur in the copy. These errors are replicated into subsequent copies. If the change isn't fatal to the virus and causes it to stop replicating, then the virus has resulted in a mutation. If that mutation results in a changed protein that enables the virus to survive, infect or replicate better the virus will become more infectious.

Viruses that infect bacteria BACTERIOPHAGES Viruses that infect bacteria

VIRAL DISEASES HIV (retrovirus) Smallpox Flu Chicken Pox Common Cold

VACCINES Vaccines are weakened viruses or pathogens that help prompt the body to create the proper immune response to give an individual protection from the virus. Why do you only get chicken pox once? 11