IB Biology SL 1.3.1 Gene mutations Question Bank
Practise IB Biology SL 1.3.1 by defining gene mutation and explaining how nucleotide changes produce new alleles.
- Syllabus
- First assessment 2025
- Course
- Biology SL
- Level
- SL
Practise IB Biology SL 1.3.1 by defining gene mutation and explaining how nucleotide changes produce new alleles.
Psammonobiotus balticus belongs to a group of protists (unicellular eukaryotic organisms) that have a shell surrounding most of the cell, which provides shelter from predators. The graph shows the frequency of varying shell lengths in a population of P. balticus.

Mutations may increase variation within a species. Compare and contrast substitution and insertion mutations.
Similarity:
a. both involve changes in the sequence of DNA/bases/nucleotides/triplets
OR
both may cause the production of a different amino acid/protein/polypeptide;
Difference:
b. substitution changes a base/nucleotide while insertion adds a base/nucleotide
OR
substitution changes one triplet while insertion changes more / causes frameshift
OR
substitution may not change protein/polypeptide function while insertion usually does;
Marking guidance:
Accept codon in place of triplet.
b. the contrast between substitution and insertion must be clear.
2
max