2019HSCShort answer

Q28 (a)

2 marks

Question

Huntington’s disease is an autosomal dominant condition caused by a mutation of a gene on chromosome 4. It causes nerve cells to break down.
Stargardt disease is an autosomal recessive condition caused by a mutation of a different gene on chromosome 4. It causes damage to the retina.
A patient is heterozygous for both Huntington’s (Hh) and Stargardt disease (Rr). His father’s extended family has numerous cases of both of these diseases. His mother does not have either disease and is homozygous for both genes.

Complete the tables, showing the TWO alleles the patient inherited from each parent.

Uncropped source page 20 for question 28.a; requires human review and cropping — Reviewed visual · source page 20

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Solution

Criteria	Marks
Suitable alleles identified for both parents	2
Provides some relevant information	1

Sample answer:

Alleles from father	Alleles from mother
H, r	h, R

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Syllabus alignment

Module 5 · Heredity

Genetic VariationInterpret inheritance patterns, pedigrees and Punnett squares to model genotype combinations.

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