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A3.1.8—Unity and diversity of genomes within species

Members of a species share most genomic information, while alleles, SNPs, recombination, organelle DNA, and population history create individual variation.

Syllabus
First assessment 2025
Objective
A3.1.8
Level
HL

Exam analysis

Chance of appearing6%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1
Typical marks1–2

Common command terms

  • Compare
  • Discuss
  • Determine
  • Contrast
  • State
  • Distinguish
  • Calculate

Scoring notes

Common mistake
Assuming every SNP changes the proteome rather than recognising that it always changes the genome.

Recent exam appearances

November 2025Paper1A ["HL"] · TZ322[ 1 ]A3.1.8—Unity and diversity of genomes within species
November 2024Paper3 ["HL"] · TZ012(b)[ 2 ]A3.1.8—Unity and diversity of genomes within species
May 2022Paper1 ["HL"] · TZ210[ 1 ]A3.1.8—Unity and diversity of genomes within species
May 2021Paper1 ["HL"] · TZ210[ 1 ]A3.1.8—Unity and diversity of genomes within species
May 2019Paper1 ["HL"] · TZ219[ 1 ]A3.1.8—Unity and diversity of genomes within species
Practice this objective

Coverage 2015–2025 · Updated 15 Jul 2026

Concept essentials

  • A genome includes all DNA in the organism, including organelle DNA where present.
  • Individuals in a species share many genes but can carry different alleles.
  • Meiosis and fertilisation generate unique combinations of chromosomes and alleles.
  • SNPs are single-base genome differences that may or may not alter proteins.
  • Haplotype and allele-frequency data reveal population-level genetic diversity.
ConceptIB Biology HL