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IB Biology HL D3.2.13 Pedigree Charts Questions

Analyse pedigree generations and affected-phenotype transmission to classify inheritance and deduce genotypes or probabilities in IB Biology HL D3.2.13.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Infer autosomal dominant, autosomal recessive or X-linked inheritance from affected individuals, unaffected parents and sex-specific transmission in a pedigree.
  • Deduce a specified individual genotype or offspring probability from a pedigree and its inheritance pattern.

IB Biology HL D3.2.13 Pedigree Charts Questions question 1

[Maximum number: 3]

In late-onset Tay-Sachs disease, neurological disorders slowly appear in adults. The pedigree chart shows four generations of a family affected by the disease.

Figure for Question IB Biology HL D3.2.13 Pedigree Charts Questions question 1 — IB Biology HL

Question (a)

(a)

Determine the type of inheritance shown in the pedigree chart.

[ 1 ]

Question (b)

(b)

At the gene locus for the disease, the alleles are N and n . Deduce the genotype of the person identified as

[ 2 ]

Question (i)

(i)

At the gene locus for late-onset Tay-Sachs disease, the alleles are N and n. Deduce the genotype of the person identified as A.

[ 1 ]

Question (ii)

(ii)

At the gene locus for late-onset Tay-Sachs disease, the alleles are N and n. Deduce the genotype of the person identified as B.

[ 1 ]
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