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A3.1.7—Karyotyping and karyograms

Karyotyping photographs and arranges chromosomes so chromosome number, sex chromosomes, abnormalities, homologous pairs, and species-level differences can be interpreted accurately.

Syllabus
First assessment 2025
Objective
A3.1.7
Level
HL

Exam analysis

Chance of appearing8%of analysed past papers
Latest appearanceMay 2025
Most common paperPaper1
Typical marks1

Common command terms

  • State
  • Determine
  • Explain
  • Analyse
  • Identify
  • Outline
  • Compare
  • Distinguish
  • Justify
  • Describe
  • Draw

Scoring notes

Common mistake
Treating karyotyping as a test for individual gene mutations rather than chromosome-level abnormalities.

Recent exam appearances

May 2025Paper1A ["HL"] · TZ122[ 1 ]A3.1.7—Karyotyping and karyograms
May 2025Paper1B ["HL"] · TZ31(c)[ 4 ]A3.1.7—Karyotyping and karyograms
November 2019Paper1 ["HL"] · TZ011[ 1 ]A3.1.7—Karyotyping and karyograms
May 2019Paper2 ["HL"] · TZ12(c)(ii)[ 1 ]A3.1.7—Karyotyping and karyograms
May 2019Paper2 ["HL"] · TZ12(c)(i)[ 1 ]A3.1.7—Karyotyping and karyograms
Practice this objective

Coverage 2013–2025 · Updated 15 Jul 2026

Concept essentials

  • Karyograms arrange homologous chromosomes by size, banding pattern, and centromere position.
  • Sex can be inferred from sex chromosomes when the species sex-determination system is known.
  • Trisomies and other chromosome-number abnormalities are visible in karyograms.
  • Prenatal karyotyping requires fetal cells, such as cells from chorionic villi or amniotic fluid.
  • Karyotyping works at chromosome scale, not at single-gene sequence scale.
ConceptIB Biology HL