lesson 3 viruses. virus tiny “organism” that is parasitic to cells composed of two main parts:...
TRANSCRIPT
Virus
• Tiny “organism” that is parasitic to cells• Composed of two main parts:• Protein outer shell called capsid• Genetic material inside (DNA or RNA)
• Not classified as living• Do not have cells• Require cells to replicate
• Likely evolved after cells came into existence
Virus
• Cause some of the most common illnesses, ex:• Common cold, the flu, cold sores, etc
• Cause some of the deadliest diseases, ex:• Ebola, avian flu, AIDS
Virus
• Cannot be killed by antibiotics• Antibiotics kill bacteria
• People can be protected against viruses with vaccines• Ex. Flu shot
RNA or DNA?
• Viruses with RNA (higher mutation rate)• Human immunodeficiency virus (HIV)• Influenza viruses• Rabies• Measles, mumps, pneunomia, polio, common cold• SARS
• Viruses with DNA (usually stable/constant, vaccines effective )• Chickenpox, cold sores, genital herpes• Mononucleosis• Hepatitis• Respiratory infections, tumours
Virus Shapes
1. Helical (a spiral rod)
2. Polyhedral (many sides)
3. Complex (polyhedral capsid attached to a helical tail)
Viruses are host cell specific• Viruses usually infect only 1 type of host or even
one cell type• Some viruses can infect many species• Ex. Rabies, swine flu
How are viruses spread?
• Vectors – carriers of viruses from one host to another• May include:• Insects (yellow fever, West Nile)• Animals (rabies)• Water (polio)• Air (influenza, common cold, chicken pox)• Humans (influenza, hepatitis, HIV)
Virus applications
• Studying molecular biology• Genetically modify organisms• Virotherapy: using viruses to treat diseases• Kill bacteria• Kill cancer
• Insecticide• Biological warfare
Homework
1. What is a virus?2. Are viruses alive? Why or why not?3. Name 2 characteristics of viruses4. What is the difference between a host and a
parasite?5. What are 3 different vectors for viruses?6. Can a tobacco mosaic virus infect a human? Why
or why not?7. Describe the life cycle of a virus.