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IB Biology HL 2.5.13 Complex pedigree inheritance analysis Question Bank

Practise IB Biology HL 2.5.13 by analysing complex pedigrees to deduce allele behaviour and genotypes.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Deduce autosomal, X-linked or dominant-recessive inheritance from pedigree evidence.
  • Infer individual genotypes and evaluate inherited-disorder probabilities.

D3.2.13—Pedigree charts 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 D3.2.13—Pedigree charts 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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