Q BankQuestion BankDocsDocuments

D2.2.10 (HL)—Monozygotic twin studies

Monozygotic twin studies separate shared genome effects from environmental and epigenetic differences that accumulate over time in individuals and tissues.

Syllabus
First assessment 2025
Objective
D2.2.10
Level
HL

Exam analysis

Chance of appearing2%of analysed past papers
Latest appearanceNovember 2021
Most common paperPaper3
Typical marks1–3

Common command terms

  • Identify
  • Compare
  • Analyse

Scoring notes

Common mistake
Using only numerical values without comparing identical and non-identical twins.

Recent exam appearances

November 2021Paper1 ["HL"] · TZ027[ 1 ]D2.2.10 (HL)—Monozygotic twin studies
November 2013Paper3 ["HL"] · TZ04(c)[ 3 ]D2.2.10 (HL)—Monozygotic twin studies
November 2013Paper3 ["HL"] · TZ04(b)[ 3 ]D2.2.10 (HL)—Monozygotic twin studies
November 2013Paper3 ["HL"] · TZ04(a)[ 1 ]D2.2.10 (HL)—Monozygotic twin studies
Practice this objective

Coverage 2013–2021 · Updated 16 Jul 2026

Concept essentials

  • Monozygotic twins share essentially the same genome.
  • Differences between identical twins can involve epigenetic or environmental factors.
  • Greater similarity in identical than non-identical twins can support genetic influence.
  • Adult identical twins may differ in methylation pattern.
ConceptIB Biology HL