D1.3 Mutation and gene editing
Mutation and gene editing explain how DNA sequence changes arise, affect proteins, create variation and can be studied or altered deliberately.
- Syllabus
- First assessment 2025
- Topic
- D1.3
- Level
- SL
Exam analysis
Chance of appearing14%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1
Typical marks1–2
Most tested objectives
Common question formats
- Definition or recall
- Process explanation
- Comparison
- Evaluation
- Diagram interpretation
- Calculation
Recent exam appearances
November 2025Paper1A ["SL"] · TZ17[ 1 ]D1.3.6—Consequences in germ vs. somatic cells
November 2025Paper1B ["SL"] · TZ14(d)(ii)[ 1 ]D1.3.4—Causes of mutation
November 2025Paper1B ["SL"] · TZ14(d)(i)[ 1 ]D1.3.4—Causes of mutation
November 2025Paper1B ["SL"] · TZ14(b)[ 1 ]D1.3.4—Causes of mutation
May 2025Paper1A ["SL"] · TZ38[ 1 ]D1.3.5—Randomness in mutation
Practice this topic
Coverage 2010–2025 · Updated 16 Jul 2026
Objective notes
7 learning objectives• Gene mutations are changes in the base sequence of DNA
• Main types are substitution, insertion, deletion, and duplication
• Base substitutions can create SNPs and change codons
• Degeneracy can make substitutions silent, missense, or nonsense
• Insertions or deletions not in multiples of three cause frameshifts
• Frameshifts alter downstream codons and often disrupt protein function
• Mutations can arise from replication errors, repair errors, or chromosome damage
• Mutagens include chemicals, ionizing radiation, and ultraviolet radiation
• Mutations occur randomly with respect to organism need or advantage
• Mutation rate varies with DNA sequence, gene expression, repair, and mutagen exposure
• Germ-line mutations can be inherited by offspring
• Somatic mutations affect only descendant body cells and can contribute to cancer
• Mutation is the original source of new alleles and genetic variation
• Many mutations are neutral or harmful, but variation supplies material for natural selection