1. Viruses  Is it living?  Shapes/Structure  Replication  Types of viruses

2. Are Viruses Living????  Viruses are segments of nucleic acids enclosed in a protein capsid  Very, Very small  Contain either RNA or DNA  Considered to be non-living because they do not carry on life process on their own for example movement and reproduction. In addition they: - do not grow - do not have homeostasis - do not metabolize

3. Structure Capsid: protein coat surrounding nucleic acid Envelope: membrane-like structure outside the capsid (can have or not can an envelope) Glycoprotein: projections used to attach to a host cell. Capsid DNA/RNA Glycoprotein HIV virus Envelope

4. Shapes of viruses 2 shapes -Helical: Rod-like appearance, with capsid proteins winding around the core in a spiral EX: Rabies Virus Tobacco Mosaic virus

5. Shapes Con’t Icosahedral - 20 triangular faces: herpes, chickenpox, polio Herpes Virus

6. Common Viruses to Humans Viral groupNucleic ShapeDiseases Acid StructureCaused PapovavirusesDNA I, NE Warts, Cancer AdenovirusesDNA I, NE Respiratory, Intestinal Infection HerpesviruesDNA I, E herpes, chickenpox, shingle, Mono PicornvirusesRNA I, NE Hepatitis, Cancer MyxoviruesRNA H,E Influenza A, B, C RhabdoviruesRNA H, E Rabies RetrovirusesRNA I, E AIDS, Cancer

7. Virus Types 1. DNA: Works in 2 ways - Virus enters the cell and directly produces RNA to make viral proteins proteins - Viruses DNA joins with the host cell DNA to make new viruses 2. RNA - RNA enters in the host cell’s cytoplasm. It then uses the ribosomes to make new viral proteins. - RNA enters in the host cell’s cytoplasm. It then uses the ribosomes to make new viral proteins. 3. Retroviruses - Contain an enzyme called reverse transcriptase: causes DNA to be made from RNA. The DNA becomes part of the host DNA/Genes. Then new RNA is made from this new DNA. RNA makes new viral proteins. - Contain an enzyme called reverse transcriptase: causes DNA to be made from RNA. The DNA becomes part of the host DNA/Genes. Then new RNA is made from this new DNA. RNA makes new viral proteins. 4. Viroid: short, single strand of RNA, no capsid. They interfere with plant metabolism and has destroyed entire crops (potatoes, cucumbers, oranges) 5. Prions: 250 amino acids and have no nucleic acid. Linked to brain diseases such as scrapie (slow degeneration of nervous system in sheep) and Mad Cow (brain disease in cows)

8. Replication:Bacteriophage Bacteriophage: - viruses that infect bacteria - T-4 bacteriophage- Escherichia coli- found in human digestive tract - composed of icosahedral head contain nucleic acids. -Tail composed of the collar and sheath; this helps to inject Collar nucleic acid into the host cell. - Tail Fibers: attached to the Tail base plate help attach to host cell base plate

9. Replication Cycles  Lytic Cycle - They are virulent: cause disease - They are virulent: cause disease - A virus invades a host cell, produces new viruses, - A virus invades a host cell, produces new viruses, destroys the host cell, and releases new viruses. destroys the host cell, and releases new viruses.  Lysogenic Cycle - infects the cell without causing immediate harm. - these viruses can stay in the host for a long period of time. time. - Called a temperate virus - When the DNA is injected into the host cell, it does not start to make new viral parts immediately, they will become part of the host’s DNA. When the cell is replicated naturally by the host, the virus is also being replicated. - this can become virulent.

10. Lytic Cylce: 1. Attachment/Adsorption Adsorption of a Bacteriophage to the Cell Wall of the Bacterium Attachment sites on the virus bind to corresponding receptors on the host cell wall.

11. Lytic Cycle: 2. Injection/Penetration The bacteriophage injects its genome (DNA) into the bacterium's cytoplasm

12. Lytic Cycle: 3. Viral Replication and Assembly The viral genome directs the host cell's metabolic machinery (ribosomes, tRNA, nutrients, energy, enzymes, etc.) to make viral enzymes and viral parts. The capsids assemble around the viral genomes as the viral tails assemble. (they are replicating viral parts)

13. Lytic Cycle 4. Release Release of the Bacteriophages by Lysis of the Bacterium A bacteriophage-coded enzyme breaks down the peptidoglycan in the bacterial cell wall causing osmotic lysis.

14. Treatments Antiviral Drugs Antiviral Drugs Vaccines Vaccines Animal Control: mosquitoes, rabies, Animal Control: mosquitoes, rabies, Antibiotics are not a treatment for viruses Antibiotics are not a treatment for viruses