1. Viral Reproduction

2. Viruses If viruses are non-living, how do they replicate?? They need a host cell! Before a virus can replicate, it must attach to and infect a living cell. What kinds of cells? A virus is specific to a specific kind of cell.

3. Viral attachment Viruses are specific to certain host cells. They will only attach to a cell if the protein in its capsid or envelope matches the host cell’s protein. Like an enzyme (lock and key). If an virus can’t attach, it can’t infect the cell.

4. What happens after attachment? Once a suitable host is found, the virus attaches and injects its DNA into the host. The host cell drives the production of new virus particles.

5. Viral Replication Once in a host, the virus can take one of two paths. 1. Lytic Cycle2. Lysogenic Cycle

6. Two types of viral life cycles Lytic cycle The rapid reproduction of the entire virus carried out by the host eventually bursting the host cell.

7. Virus Replication-Lytic Cycle 1. Attachment 3. Replication and production of viral particles 4. Lysis and release of viral particles (cell destruction) 2. Insertion of DNA into host cell

8. The Lytic Cycle WATCH IT! WATCH IT!

9. Two types of viral life cycles Lytic cycle The rapid reproduction of the entire virus carried out by the host eventually bursting the host cell. Lysogenic cycle The viral DNA is integrated into a host and is replicated without destroying the cell. Eventually, the virus exists the lysogenic cycle and enters the lytic cycle.

10. 1. Attachment Virus Replication- Lysogenic Cycle 3. Integration of viral DNA into host DNA (called a provirus). 2. Insertion of DNA into host cell 5. Production of new host cell that is already infected. 4. Viral DNA is replicated with host DNA. 6. New cells continue to replicate and divide.

11. Virus Replication- Lysogenic Cycle Each time the cell divides, the provirus also divides. Each generation results in two infected host cells. Does not destroy host cell until provirus enters the lytic cycle.

12. The Lysogenic Cycle WATCH IT! WATCH IT!