D2.1.10—Down syndrome
Down syndrome usually results when non-disjunction produces a gamete with an extra chromosome 21, causing trisomy after fertilization occurs in reproduction.
- Syllabus
- First assessment 2025
- Objective
- D2.1.10
- Level
- HL
Exam analysis
Chance of appearing4%of analysed past papers
Latest appearanceMay 2024
Most common paperPaper1
Typical marks1
Common command terms
- Explain
- Outline
- Determine
- State
- Identify
- Describe
Scoring notes
- Common mistake
- Calling Down syndrome a gene mutation instead of a chromosome-number abnormality.
Recent exam appearances
May 2024Paper2 ["HL"] · TZ27(b)[ 4 ]D2.1.10—Down syndrome
November 2020Paper1 ["HL"] · TZ013[ 1 ]D2.1.10—Down syndrome
May 2018Paper1 ["HL"] · TZ217[ 1 ]D2.1.10—Down syndrome
May 2013Paper2 ["HL"] · TZ22(b)(ii)[ 1 ]D2.1.10—Down syndrome
May 2013Paper1 ["HL"] · TZ111[ 1 ]D2.1.10—Down syndrome
Practice this objective
Coverage 2013–2024 · Updated 16 Jul 2026
Concept essentials
- Non-disjunction is failed chromosome separation during meiosis.
- Non-disjunction can produce gametes with extra or missing chromosomes.
- Down syndrome is usually caused by trisomy 21.
- A karyogram can identify the chromosome affected by trisomy.