CourseCourseConceptConceptDocumentDocument

IB Biology HL D1.3 Mutation and Gene Editing Questions

Practise IB Biology HL D1.3 by classifying mutations, predicting molecular consequences and evaluating gene knockout and CRISPR evidence.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • define gene mutations and distinguish substitution, insertion and deletion in DNA sequences
  • deduce codon and amino-acid outcomes of substitutions, including silent, missense and nonsense changes
  • link a substitution to altered haemoglobin structure, red-cell shape and sickle-cell function
  • explain chemical mutagen effects and evaluate NNK tumour evidence using dose and model limits
  • explain random mutation as a source of new alleles and population variation
  • use gene-knockout phenotypes or p53-knockout mice to investigate gene function and drug effects
  • apply CRISPR-Cas9 to target dystrophin mutations by replacing, inserting or deleting DNA
  • identify conserved protein stretches from sequence-alignment evidence

Covered syllabus points

D1.3.1—Gene mutationsD1.3.2—Base substitution consequencesD1.3.3—Insertion and deletion consequencesD1.3.4—Causes of mutationD1.3.5—Randomness in mutationD1.3.6—Consequences in germ vs. somatic cellsD1.3.7—Mutation as source of variationD1.3.8 (HL)—Gene knockoutD1.3.9 (HL)—CRISPR-Cas9 gene editingD1.3.10 (HL)—Conserved sequences

Question 1

[Maximum number: 4]

Duchenne muscular dystrophy (DMD) is a sex-linked genetic disorder caused by a recessive allele resulting from mutations in the X-linked dystrophin gene. This causes the degeneration of cardiac and skeletal muscle. These mutations can include deletions, insertions and base substitution mutations.

Question (a)

(a)

Distinguish between deletion and insertion mutations.

Figure for Question (a) — IB Biology HL
[ 1 ]

Question (b)

(b)

Explain ways in which CRISPR-Cas9 gene editing could be used to change the mutated dystrophin protein produced.

[ 3 ]

Question 2

[Maximum number: 5]

Outline the effects of a base substitution mutation in the case of sickle-cell anemia.

Question 3

[Maximum number: 11]

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)

State the relationship between the dose of NNK and lung tumour incidence.

[ 1 ]

Question (b)

(b)

Explain the effects of mutagens such as NNK.

[ 2 ]

Question (c)

(c)

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 (d)

(d)

Describe the results when the mice were injected with NNK.

[ 2 ]

Question (e)

(e)

Evaluate the hypothesis that nicotine is not a mutagen.

[ 3 ]
All question bank results loaded