Genetic Disorders

This lesson covers genetic disorders — conditions caused by mutations in genes that are inherited — as required by the Edexcel GCSE Combined Science specification (1SC0). You need to understand cystic fibrosis (recessive), polydactyly (dominant), how to use Punnett squares for these conditions, and the implications of genetic testing.

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What Are Genetic Disorders?

A genetic disorder is a disease or condition caused by a mutation in one or more genes. Genetic disorders can be:

• Inherited — passed from parents to offspring through their alleles.
• Caused by dominant or recessive alleles.

The two genetic disorders you need to know for Edexcel GCSE Combined Science are:

Disorder	Inheritance pattern	Allele
Cystic fibrosis	Autosomal recessive	f (recessive), F (normal dominant)
Polydactyly	Autosomal dominant	D (dominant affected), d (normal recessive)

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Cystic Fibrosis

Cystic fibrosis (CF) is a genetic disorder that affects the lungs, digestive system and other organs. It is caused by a recessive allele.

Key Facts