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D3.2.7—Phenylketonuria (PKU)

PKU is an inherited recessive condition affecting phenylalanine metabolism, managed by identifying affected individuals and controlling diet in inheritance problems.

Syllabus
First assessment 2025
Objective
D3.2.7
Level
HL

Exam analysis

Chance of appearing3%of analysed past papers
Latest appearanceMay 2025
Most common paperPaper3
Typical marks1–2

Common command terms

  • Explain
  • Outline

Recent exam appearances

May 2025Paper1A ["HL"] · TZ232[ 1 ]D3.2.7—Phenylketonuria (PKU)
May 2024Paper3 ["HL"] · TZ222(b)[ 2 ]D3.2.7—Phenylketonuria (PKU)
May 2024Paper3 ["HL"] · TZ222(a)[ 2 ]D3.2.7—Phenylketonuria (PKU)
May 2016Paper3 ["HL"] · TZ019(b)(ii)[ 1 ]D3.2.7—Phenylketonuria (PKU)
Practice this objective

Coverage 2016–2025 · Updated 16 Jul 2026

Concept essentials

  • PKU is usually autosomal recessive, so carriers can be unaffected.
  • Diet can influence the PKU phenotype by limiting phenylalanine intake.
  • The condition links an allele to an enzyme defect and a metabolic outcome.
ConceptIB Biology HL