Year 10 Science · Unit 1 · Lesson 5

Genetic Variation and Mutations

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Learning Goals

Trace the causal chain from a mutagen to disease using the because chain
Compare substitution versus insertion/deletion mutations for their effect on proteins
Apply mutation concepts to a real-world cancer example

Warm Up

Because… chain

Fill in the missing effects. Each cause leads to the next step in the chain, tracing how UV radiation can cause melanoma.

UV radiation from the sun strikes skin cells

→

A thymine dimer forms, two adjacent thymine bases bond together incorrectly

→

A mutation occurs in the BRAF gene, which normally controls cell division

→

The mutated cell divides uncontrollably, accumulating further mutations

→

Overall outcome:

Your Turn

Compare two

Complete the table to compare substitution mutations with insertion/deletion mutations.

Feature	Substitution mutation	Insertion / Deletion mutation
What changes in the DNA?
Does the reading frame shift?
How many codons are affected?
Effect on the protein produced
Example disease (if any)

Show What You Know

1. Australia has one of the highest rates of melanoma in the world, partly due to high UV radiation levels and a historically sun-exposed outdoor culture. Using your knowledge of UV radiation as a mutagen, explain the biological mechanism by which UV causes skin cancer.

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2. The BRCA1 and BRCA2 genes normally produce proteins that repair DNA. A woman with a BRCA1 mutation has a significantly higher lifetime risk of breast cancer. Explain why a mutation in a DNA repair gene (like BRCA1) would increase the risk of developing cancer.

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Wrap Up

In one sentence, what was the main idea of this lesson?