BELL WORK: Write the question AND your answer. Why can’t a person be infected by the tobacco mosaic virus?

CO: I will describe viral reproduction. LO: I will write notes and talk about the steps in viral reproduction.

Science Fact of the Day: Corneas are the only tissues that don't require blood.

OVERVIEW

Quick Write: Answer the question at the bottom of your first page. Are viruses alive? Explain why or why not.

So what happens when a virus gets into your body??

VIRUS A living thing that provides a source of energy for a virus or an organism Organisms that live on or near a host and cause harm. A tiny, nonliving structure that invades and then multiplies inside of a cell. A virus that immediately goes into action. It begins to take over cell functions and produce the virus’s proteins and genetic material. These parts then assemble into new viruses. The viruses multiply like a copy machine left on. When it is full the cell bursts open – releases the new viruses and dies. Some viruses hide for a while and become part of the cell’s genetic material. It may stay inactive and “hidden” for years. Then under certain conditions it becomes active and acts like an active virus. Ex – cold sores

Lytic Cycle Active viruses enter cells and immediately begin to multiply, leading to the quick death of the invaded cells. Steps to the lytic cycle: 1.Attach to cell 2.Inject DNA/RNA 3.Produce (replicate) virus parts 4.Assemble new virons 5.Release viruses to infect other cells

Lytic Cycle - Viruses

Lysogenic Cycle Hidden viruses “hide” for a while inside host cells before becoming active Steps to the Lysogenic Cycle: 1.Attach to cell 2.Inject DNA/RNA 3.Integrate DNA/RNA into cell 4.Wait 5.Remove DNA/RNA 6.Become active (lytic cycle)

Lysogenic Cycle - Viruses

Rally Robin: Cycle Steps Get into partners—decide who is partner A and who is partner B. – Partner A: Describe the steps for the Lytic cycle. – Partner B: Draw each step. After a few minutes, we will switch to the Lysogenic Cycle and you will switch roles.

Lytic CycleLysogenic Cycle Attach to cells Inject DNA/RNA into cells Virus takes over the nucleus Viral reproduction Happens immediately Causes cell death quickly Active viruses One example is flu Virus hides Integrate DNA/RNA into the cell Virus waits Hidden viruses One example is HIV Happens more slowly

Could viruses be helpful?

- Since viruses can transport DNA and RNA into cells, scientists are exploring Gene Therapy - In Gene Therapy, viral genetic material is replaced with new DNA - In time, this could be used to cure genetic diseases. Currently we have no cure for these types of illnesses

You decide…Lytic or Lysogenic Dengue Fever

For spread of infection thurs.. Could we be the Last of Us?