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IB Biology HL D2.1.10 Down Syndrome Questions

Analyse how failed chromosome separation creates abnormal gametes and can produce Down syndrome in IB Biology HL D2.1.10.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Identify the meiotic stage and homologous- or sister-chromatid separation failure responsible for non-disjunction.
  • Use karyotype or chromosome-number evidence to diagnose aneuploidy and its meiotic origin.

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Study D2.1.10—Down syndrome conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

IB Biology HL D2.1.10 Down Syndrome Questions question 1

[Maximum number: 1]

In a strain of soybeans, high oil content (H) in seeds is dominant to low oil content (h) and four seeds in a pod (F) is dominant to two seeds in a pod (f). A farmer crosses two soybean plants, both with high oil content and four seeds in a pod. The offspring have a phenotypic ratio of 9: 3: 3: 1.

The image shows the karyotype of a person who developed as a female.

Figure for Question IB Biology HL D2.1.10 Down Syndrome Questions question 1 — IB Biology HL

Determine, with a reason, whether this karyotype shows that non-disjunction has occurred.

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