Lesson 7 of 9 / Mutation, cell division and cancer
Why division needs checkpoints
How do risk factors affect control without guaranteeing cancer?
I can explain the need for tight cycle regulation and identify genetic, chemical and ionising-radiation risk factors.
I can explain mitotic-cycle significance and the need for tight regulation.Syllabus
Syllabus 8876, Core 2(h). Explain mitotic-cycle significance and the need for tight regulation.
I can identify genetic, chemical and ionising-radiation cancer risk factors.Syllabus
Syllabus 8876, Core 2(i). Identify genetic, chemical and ionising-radiation cancer risk factors.
About 5 min
Make a guess. You are not marked.
Is cancer just normal tissue repair happening faster than usual?
Show the answer
Cancer cells have lost normal division control.
Repair stops when a tissue is restored. Cancer cells ignore the checks that should stop them.
The key idea
Cell-cycle control normally prevents inappropriate division. Mutations and damaging exposures can disrupt control, increasing the chance of cancerous growth.
Explore the idea
A checkpoint must control progression
Normal controls coordinate progression with cell condition. H1 does not require the named molecular checkpoint regulators.
Explanation
A tissue needs cells to divide at suitable times and stop when appropriate. Checkpoints coordinate events such as DNA replication, integrity and chromosome attachment with progression through the cycle. H1 requires the importance of regulation, not the detailed molecular checkpoint machinery.
If control is disrupted, damaged cells may continue dividing and pass altered DNA to descendants. Failure to regulate division can contribute to uncontrolled growth. One failed control is not a complete explanation of every cancer, because development commonly requires several changes.
Inherited genetic variants can increase susceptibility. Chemical carcinogens can damage DNA or promote changes associated with cancer; tobacco-smoke chemicals are a familiar example. Ionising radiation can damage DNA, including causing strand breaks.
A risk factor increases probability; it does not mean every exposed person develops cancer or that every cancer has one identifiable exposure. Cells possess repair and removal mechanisms, and the effect depends on exposure and biological context. A reasoned explanation states the increased chance and the mechanism without promising a deterministic outcome.
Step by step
- 1
State normal control
Progression should depend on appropriate completion and checking of earlier events.
- 2
Identify a source of change
Inherited susceptibility, chemicals and ionising radiation can contribute differently.
- 3
Use probability language
A risk factor can increase the chance of mutations or dysregulation, not guarantee a tumour.
Worked example
An incomplete causal claim
A student says, "One exposure to radiation always creates cancer immediately." Correct the reasoning.
One way to explain it
Ionising radiation can damage DNA and increase cancer risk, but damage may be repaired or the affected cell removed. Cancer commonly develops through accumulated changes over time, so one exposure does not guarantee immediate cancer.
Why this answer works
- Retain the real risk mechanism.
- Remove the unjustified certainty and timescale.
Watch out for this
A student says: "Cancerous growth is simply normal tissue repair happening faster." What is wrong with this?
Show the answer
Repair is regulated to meet tissue needs. Cancer involves loss of normal controls and other acquired properties.
Check your understanding
Why is tight regulation of division necessary?
Show the answer
To prevent inappropriate proliferation and transmission of damaged genetic material.
Division should occur under suitable, checked conditions.
Quick recall
How do risk factors affect control without guaranteeing cancer?