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Science

Inheritance

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Huntington’s disease

Huntington’s disease is an inherited disorder that affects the nervous system. It is caused by a dominant allele. This means it can be passed on by just one parent if they have the disorder. The genetic diagram shows how this can happen.

The Huntington's allele is represented by H. The normal allele is h. Suppose 'Parent 1' has Huntingdon's, then they are Hh. 'Parent 2' does not - they are hh. The possible combinations of alleles in the children are Hh, Hh, hh and hh. So it is possible for the children to get the disease if only one parent has it

Genetic diagram to show the inheritance of Huntingdon's disease

Note that if you are doing the Foundation Tier paper you are expected to be able to interpret genetic diagrams. If you are doing the Higher Tier paper, you are expected to be able to draw genetic diagrams for any combination of dominant and recessive alleles.

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