Remember! Viruses are specific! Once a virus attaches to a cell, what happens?

Viral Reproduction

Viral Infections Once a virus enters a host cell, 1 of 2 processes will occur: – Lysogenic Cycle – Lytic Cycle

The Lytic Cycle

1.Viral DNA (or RNA) is injected into the host cell 2.Host cell begins to make mRNA from the viral DNA 3.Viral proteins shut down the host cell’s regular functions 4.Cell is used to make thousands of viruses 5.Host cell bursts (lyses) & releases viruses to infect other cells This is a cell lysing. Viruses burst out of the cell!

The Lysogenic Cycle

1.Viral DNA (or RNA) is injected into the host cell 2.DNA is integrated (joined) into the host DNA 3.Host cell continues dividing with the virus DNA 4.Eventually, the viral DNA can be triggered to enter the Lytic Cycle! Cold sores are caused from a type of herpes virus. This virus enters the Lysogenic Cycle, but can enter the Lytic Cycle if your immune system is weakened. This is when you get a cold sore!

The Lytic & Lysogenic Cycles

Which cycle will spread the viral infection? A.Lytic Cycle B.Lysogenic Cycle C.Both Both!

Which cycle can cause disease? A.Lytic Cycle B.Lysogenic Cycle C.Both Both!

Which cycle will assemble new viruses? A.Lytic Cycle B.Lysogenic Cycle C.Both The Lytic Cycle!

Which cycle is more sneaky? A.Lytic Cycle B.Lysogenic Cycle C.Both The Lysogenic Cycle! Even if the cold sore goes away, the virus never does…

What is the correct sequence of events of the Lytic Cycle? Try to do this without looking at your notes. Use logic! A.Injection, Transcription, Translation, Assembly, Lysis B.Injection, Assembly, Translation, Transcription, Lysis C.Lysis, Assembly, Injection, Transcription, Translation D.Assembly, Transcription, Translation, Lysis, Injection A. Injection, Transcription, Translation, Assembly, Lysis

RNA Viruses RNA viruses do not have built in proofreading, so they mutate & evolve QUICKLY! A special type of RNA virus, a retrovirus, can cause DNA to be made from their RNA. – Some cancers & AIDS are caused by retroviruses! Human Immunodeficiency Virus

Lytic vs. Lysogenic Cycle Answer the questions & complete the table. Don’t turn it in yet!