The Viral Lifecycle Lab
A virus has two ways to make more of itself: burst the cell now, or hide inside its DNA and wait. Learn the lytic and lysogenic pathways, and never mix them up again.
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The Viral Lifecycle Lab 🦠
A virus is not even a cell, so it cannot reproduce on its own. It has to hijack a living host cell to make copies of itself. There are **two ways** it can do this, and telling them apart is exactly what this Higher-tier topic is testing.
Two pathways 🧬
Once a virus has entered a host cell, it follows one of two pathways: • The **lytic** pathway: make copies **straight away** and burst the cell. • The **lysogenic** pathway: **hide** inside the host DNA and wait.\n\nWe will take them one at a time, starting with the lytic pathway.
The lytic pathway 💥
In the **lytic** pathway the virus goes to work immediately: • It injects its **genetic material** into the host cell. • It hijacks the cell's machinery to make **many copies** of the virus. • The new viruses assemble, and the cell **bursts (lysis)**, releasing them to infect more cells. It is fast and it **destroys the host cell**.
The lytic cycle
An interactive activity.
Which pathway is this?
A virus infects a cell, immediately makes hundreds of copies, and the cell bursts open. Which pathway is this?
- The lytic pathway, because it replicates at once and destroys the cell
- The lysogenic pathway
- Neither, because viruses cannot reproduce inside cells
- Both pathways happening at the same time
The lysogenic pathway 😴
The **lysogenic** pathway plays a longer game: • The **viral DNA is inserted into the host cell's own DNA** (its genome), where it becomes a dormant **provirus**. • Every time the host cell **divides**, the viral DNA is **copied along with it**, spreading silently and doing no immediate harm. It can stay dormant for many cell generations.
Match each term to its meaning
- Lytic pathway
- Lysogenic pathway
- Provirus
- Lysis
- Immediate replication that bursts the host cell
- Viral DNA incorporated into the host genome, staying dormant
- The dormant viral DNA sitting inside the host cell's DNA
- The bursting of the host cell to release new viruses
The switch ⚡
The lysogenic pathway is not the end of the story. A **trigger**, such as stress or a chemical, can switch the dormant provirus into the **lytic** pathway. The viral DNA then leaves the host genome, replication begins, and the cell is burst as before. So a lysogenic infection can turn lytic later.
From dormant to deadly
An interactive activity.
True about the pathways
Select ALL THREE statements about the viral lifecycle that are TRUE.
- In the lytic pathway the host cell bursts to release new viruses
- In the lysogenic pathway the viral DNA is incorporated into the host genome
- A lysogenic infection can later switch to the lytic pathway
- The lytic pathway keeps the virus dormant for years
- The lysogenic pathway immediately bursts the cell
- A virus can replicate on its own without a host cell
Lifecycle summary
A virus reproduces inside a host cell by one of two pathways. In the _____ pathway it makes copies at once and the cell bursts, a process called _____. In the lysogenic pathway the viral DNA is incorporated into the host _____ and stays dormant, but a trigger can later switch it to the _____ pathway.