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IB Biology HL 1.3.4 Causes of mutation and causal evidence Question Bank

Practise IB Biology HL 1.3.4 by analysing mutagen mechanisms and evaluating evidence for a causal link to disease.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Explain how a chemical mutagen can damage DNA or alter gene expression.
  • Evaluate dose, controls and alternative explanations in evidence linking a mutagen to cancer.
  • Distinguish correlation from causation when interpreting exposure and disease graphs.

D1.3.4—Causes of mutation question 1

[Maximum number: 10]

Tobacco smoke contains a number of mutagens that are known to induce lung tumours in rodents, including NNK, a nitrosamine. The graph shows the relationship between NNK and lung tumour incidence in male rats. NNK was administered by subcutaneous injection for 20 weeks. Data points on the graph show percentage incidence of lung cancer in treatment groups of between 20 and 80 rats.

Graph removed for copyright reasons

Question (a)

(a)

Explain the effects of mutagens such as NNK.

[ 2 ]

Question (b)

(b)

Rates of lung cancer in smokers are high. Discuss whether it can be concluded from the evidence in the two graphs that NNK causes lung cancer in smokers.

Nicotine addiction is the reason that people continue to smoke. Nicotine replacement therapy (NRT) is often used to help people quit smoking. Concerns about the safety of NRT led to a study where mice were given nicotine in drinking water and NNK was administered by subcutaneous injection. The table shows the effect of nicotine consumption on NNK-induced lung tumours in the mice.

Table removed for copyright reasons

[ 3 ]

Question (c)

(c)

Describe the results when the mice were injected with NNK.

[ 2 ]

Question (d)

(d)

Evaluate the hypothesis that nicotine is not a mutagen.

[ 3 ]
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